diff --git a/ExtUtils-ParseXS-3.35-Upgrade-to-3.39.patch b/ExtUtils-ParseXS-3.35-Upgrade-to-3.39.patch new file mode 100644 index 0000000..a18bfae --- /dev/null +++ b/ExtUtils-ParseXS-3.35-Upgrade-to-3.39.patch @@ -0,0 +1,4743 @@ +From c85261a4cef59150c379ff88a21d0f9ca6374dc2 Mon Sep 17 00:00:00 2001 +From: Jitka Plesnikova +Date: Thu, 24 May 2018 09:57:37 +0200 +Subject: [PATCH] Upgrade to 3.39 + +--- + Changes | 6 + + lib/ExtUtils/ParseXS.pm | 14 +- + lib/ExtUtils/ParseXS/Constants.pm | 2 +- + lib/ExtUtils/ParseXS/CountLines.pm | 2 +- + lib/ExtUtils/ParseXS/Eval.pm | 6 +- + lib/ExtUtils/ParseXS/Utilities.pm | 2 +- + lib/ExtUtils/Typemaps.pm | 6 +- + lib/ExtUtils/Typemaps/Cmd.pm | 2 +- + lib/ExtUtils/Typemaps/InputMap.pm | 2 +- + lib/ExtUtils/Typemaps/OutputMap.pm | 2 +- + lib/ExtUtils/Typemaps/Type.pm | 2 +- + lib/perlxs.pod | 2354 ++++++++++++++++++++++++++++++++++++ + lib/perlxstut.pod | 1401 +++++++++++++++++++++ + lib/perlxstypemap.pod | 711 +++++++++++ + t/XSTest.xs | 1 + + t/XSUsage.xs | 2 + + 16 files changed, 4497 insertions(+), 18 deletions(-) + create mode 100644 lib/perlxs.pod + create mode 100644 lib/perlxstut.pod + create mode 100644 lib/perlxstypemap.pod + +diff --git a/Changes b/Changes +index 0181371..f9fb36e 100644 +--- a/Changes ++++ b/Changes +@@ -1,5 +1,11 @@ + Revision history for Perl extension ExtUtils::ParseXS. + ++3.36 ++ - Make generated code avoid warnings about the "items" variable ++ being unused ++ - Avoid some unused-variable warnings generated by XS code in the ++ test suite ++ + 3.35 - Mon Jul 31 17:50:00 CET 2017 + - Fix ExtUtils-ParseXS/t/*.t that needed '.' in @INC (David Mitchell) + - Remove impediment to compiling under C++11 (Karl Williamson) +diff --git a/lib/ExtUtils/ParseXS.pm b/lib/ExtUtils/ParseXS.pm +index d629cf6..e1f0940 100644 +--- a/lib/ExtUtils/ParseXS.pm ++++ b/lib/ExtUtils/ParseXS.pm +@@ -11,12 +11,12 @@ use Symbol; + + our $VERSION; + BEGIN { +- $VERSION = '3.35'; ++ $VERSION = '3.39'; ++ require ExtUtils::ParseXS::Constants; ExtUtils::ParseXS::Constants->VERSION($VERSION); ++ require ExtUtils::ParseXS::CountLines; ExtUtils::ParseXS::CountLines->VERSION($VERSION); ++ require ExtUtils::ParseXS::Utilities; ExtUtils::ParseXS::Utilities->VERSION($VERSION); ++ require ExtUtils::ParseXS::Eval; ExtUtils::ParseXS::Eval->VERSION($VERSION); + } +-use ExtUtils::ParseXS::Constants $VERSION; +-use ExtUtils::ParseXS::CountLines $VERSION; +-use ExtUtils::ParseXS::Utilities $VERSION; +-use ExtUtils::ParseXS::Eval $VERSION; + $VERSION = eval $VERSION if $VERSION =~ /_/; + + use ExtUtils::ParseXS::Utilities qw( +@@ -519,9 +519,10 @@ EOF + EOF + } + else { +- # cv likely to be unused ++ # cv and items likely to be unused + print Q(<<"EOF"); + # PERL_UNUSED_VAR(cv); /* -W */ ++# PERL_UNUSED_VAR(items); /* -W */ + EOF + } + +@@ -871,6 +872,7 @@ EOF + #XS_EUPXS(XS_$self->{Packid}_nil) + #{ + # dXSARGS; ++# PERL_UNUSED_VAR(items); + # XSRETURN_EMPTY; + #} + # +diff --git a/lib/ExtUtils/ParseXS/Constants.pm b/lib/ExtUtils/ParseXS/Constants.pm +index 2150fb8..45b5674 100644 +--- a/lib/ExtUtils/ParseXS/Constants.pm ++++ b/lib/ExtUtils/ParseXS/Constants.pm +@@ -3,7 +3,7 @@ use strict; + use warnings; + use Symbol; + +-our $VERSION = '3.35'; ++our $VERSION = '3.39'; + + =head1 NAME + +diff --git a/lib/ExtUtils/ParseXS/CountLines.pm b/lib/ExtUtils/ParseXS/CountLines.pm +index ad86b57..5b48449 100644 +--- a/lib/ExtUtils/ParseXS/CountLines.pm ++++ b/lib/ExtUtils/ParseXS/CountLines.pm +@@ -1,7 +1,7 @@ + package ExtUtils::ParseXS::CountLines; + use strict; + +-our $VERSION = '3.35'; ++our $VERSION = '3.39'; + + our $SECTION_END_MARKER; + +diff --git a/lib/ExtUtils/ParseXS/Eval.pm b/lib/ExtUtils/ParseXS/Eval.pm +index 6b06bf5..9eba5e5 100644 +--- a/lib/ExtUtils/ParseXS/Eval.pm ++++ b/lib/ExtUtils/ParseXS/Eval.pm +@@ -2,7 +2,7 @@ package ExtUtils::ParseXS::Eval; + use strict; + use warnings; + +-our $VERSION = '3.35'; ++our $VERSION = '3.39'; + + =head1 NAME + +@@ -29,7 +29,7 @@ Warns the contents of C<$@> if any. + Not all these variables are necessarily considered "public" wrt. use in + typemaps, so beware. Variables set up from the ExtUtils::ParseXS object: + +- $Package $Alias $func_name $Full_func_name $pname ++ $Package $ALIAS $func_name $Full_func_name $pname + + Variables set up from C<$other_hashref>: + +@@ -63,7 +63,7 @@ Warns the contents of C<$@> if any. + Not all these variables are necessarily considered "public" wrt. use in + typemaps, so beware. Variables set up from the ExtUtils::ParseXS object: + +- $Package $Alias $func_name $Full_func_name $pname ++ $Package $ALIAS $func_name $Full_func_name $pname + + Variables set up from C<$other_hashref>: + +diff --git a/lib/ExtUtils/ParseXS/Utilities.pm b/lib/ExtUtils/ParseXS/Utilities.pm +index bc1e098..ae25b33 100644 +--- a/lib/ExtUtils/ParseXS/Utilities.pm ++++ b/lib/ExtUtils/ParseXS/Utilities.pm +@@ -5,7 +5,7 @@ use Exporter; + use File::Spec; + use ExtUtils::ParseXS::Constants (); + +-our $VERSION = '3.35'; ++our $VERSION = '3.39'; + + our (@ISA, @EXPORT_OK); + @ISA = qw(Exporter); +diff --git a/lib/ExtUtils/Typemaps.pm b/lib/ExtUtils/Typemaps.pm +index 992d15b..a762322 100644 +--- a/lib/ExtUtils/Typemaps.pm ++++ b/lib/ExtUtils/Typemaps.pm +@@ -2,7 +2,7 @@ package ExtUtils::Typemaps; + use 5.006001; + use strict; + use warnings; +-our $VERSION = '3.35'; ++our $VERSION = '3.38'; + + require ExtUtils::ParseXS; + require ExtUtils::ParseXS::Constants; +@@ -781,7 +781,9 @@ corresponding OUTPUT code: + $var.context.value().size()); + ', + 'T_OUT' => ' { +- GV *gv = newGVgen("$Package"); ++ GV *gv = (GV *)sv_newmortal(); ++ gv_init_pvn(gv, gv_stashpvs("$Package",1), ++ "__ANONIO__",10,0); + if ( do_open(gv, "+>&", 3, FALSE, 0, 0, $var) ) + sv_setsv( + $arg, +diff --git a/lib/ExtUtils/Typemaps/Cmd.pm b/lib/ExtUtils/Typemaps/Cmd.pm +index 7ff0780..3c33f54 100644 +--- a/lib/ExtUtils/Typemaps/Cmd.pm ++++ b/lib/ExtUtils/Typemaps/Cmd.pm +@@ -2,7 +2,7 @@ package ExtUtils::Typemaps::Cmd; + use 5.006001; + use strict; + use warnings; +-our $VERSION = '3.35'; ++our $VERSION = '3.38'; + + use ExtUtils::Typemaps; + +diff --git a/lib/ExtUtils/Typemaps/InputMap.pm b/lib/ExtUtils/Typemaps/InputMap.pm +index b626973..bf19df1 100644 +--- a/lib/ExtUtils/Typemaps/InputMap.pm ++++ b/lib/ExtUtils/Typemaps/InputMap.pm +@@ -2,7 +2,7 @@ package ExtUtils::Typemaps::InputMap; + use 5.006001; + use strict; + use warnings; +-our $VERSION = '3.35'; ++our $VERSION = '3.38'; + + =head1 NAME + +diff --git a/lib/ExtUtils/Typemaps/OutputMap.pm b/lib/ExtUtils/Typemaps/OutputMap.pm +index 8c72e5b..90adb48 100644 +--- a/lib/ExtUtils/Typemaps/OutputMap.pm ++++ b/lib/ExtUtils/Typemaps/OutputMap.pm +@@ -2,7 +2,7 @@ package ExtUtils::Typemaps::OutputMap; + use 5.006001; + use strict; + use warnings; +-our $VERSION = '3.35'; ++our $VERSION = '3.38'; + + =head1 NAME + +diff --git a/lib/ExtUtils/Typemaps/Type.pm b/lib/ExtUtils/Typemaps/Type.pm +index 7909bbe..01bd51d 100644 +--- a/lib/ExtUtils/Typemaps/Type.pm ++++ b/lib/ExtUtils/Typemaps/Type.pm +@@ -4,7 +4,7 @@ use strict; + use warnings; + require ExtUtils::Typemaps; + +-our $VERSION = '3.35'; ++our $VERSION = '3.38'; + + =head1 NAME + +diff --git a/lib/perlxs.pod b/lib/perlxs.pod +new file mode 100644 +index 0000000..1419ee0 +--- /dev/null ++++ b/lib/perlxs.pod +@@ -0,0 +1,2354 @@ ++=head1 NAME ++ ++perlxs - XS language reference manual ++ ++=head1 DESCRIPTION ++ ++=head2 Introduction ++ ++XS is an interface description file format used to create an extension ++interface between Perl and C code (or a C library) which one wishes ++to use with Perl. The XS interface is combined with the library to ++create a new library which can then be either dynamically loaded ++or statically linked into perl. The XS interface description is ++written in the XS language and is the core component of the Perl ++extension interface. ++ ++Before writing XS, read the L section below. ++ ++An B forms the basic unit of the XS interface. After compilation ++by the B compiler, each XSUB amounts to a C function definition ++which will provide the glue between Perl calling conventions and C ++calling conventions. ++ ++The glue code pulls the arguments from the Perl stack, converts these ++Perl values to the formats expected by a C function, call this C function, ++transfers the return values of the C function back to Perl. ++Return values here may be a conventional C return value or any C ++function arguments that may serve as output parameters. These return ++values may be passed back to Perl either by putting them on the ++Perl stack, or by modifying the arguments supplied from the Perl side. ++ ++The above is a somewhat simplified view of what really happens. Since ++Perl allows more flexible calling conventions than C, XSUBs may do much ++more in practice, such as checking input parameters for validity, ++throwing exceptions (or returning undef/empty list) if the return value ++from the C function indicates failure, calling different C functions ++based on numbers and types of the arguments, providing an object-oriented ++interface, etc. ++ ++Of course, one could write such glue code directly in C. However, this ++would be a tedious task, especially if one needs to write glue for ++multiple C functions, and/or one is not familiar enough with the Perl ++stack discipline and other such arcana. XS comes to the rescue here: ++instead of writing this glue C code in long-hand, one can write ++a more concise short-hand I of what should be done by ++the glue, and let the XS compiler B handle the rest. ++ ++The XS language allows one to describe the mapping between how the C ++routine is used, and how the corresponding Perl routine is used. It ++also allows creation of Perl routines which are directly translated to ++C code and which are not related to a pre-existing C function. In cases ++when the C interface coincides with the Perl interface, the XSUB ++declaration is almost identical to a declaration of a C function (in K&R ++style). In such circumstances, there is another tool called C ++that is able to translate an entire C header file into a corresponding ++XS file that will provide glue to the functions/macros described in ++the header file. ++ ++The XS compiler is called B. This compiler creates ++the constructs necessary to let an XSUB manipulate Perl values, and ++creates the glue necessary to let Perl call the XSUB. The compiler ++uses B to determine how to map C function parameters ++and output values to Perl values and back. The default typemap ++(which comes with Perl) handles many common C types. A supplementary ++typemap may also be needed to handle any special structures and types ++for the library being linked. For more information on typemaps, ++see L. ++ ++A file in XS format starts with a C language section which goes until the ++first C> directive. Other XS directives and XSUB definitions ++may follow this line. The "language" used in this part of the file ++is usually referred to as the XS language. B recognizes and ++skips POD (see L) in both the C and XS language sections, which ++allows the XS file to contain embedded documentation. ++ ++See L for a tutorial on the whole extension creation process. ++ ++Note: For some extensions, Dave Beazley's SWIG system may provide a ++significantly more convenient mechanism for creating the extension ++glue code. See L for more information. ++ ++=head2 On The Road ++ ++Many of the examples which follow will concentrate on creating an interface ++between Perl and the ONC+ RPC bind library functions. The rpcb_gettime() ++function is used to demonstrate many features of the XS language. This ++function has two parameters; the first is an input parameter and the second ++is an output parameter. The function also returns a status value. ++ ++ bool_t rpcb_gettime(const char *host, time_t *timep); ++ ++From C this function will be called with the following ++statements. ++ ++ #include ++ bool_t status; ++ time_t timep; ++ status = rpcb_gettime( "localhost", &timep ); ++ ++If an XSUB is created to offer a direct translation between this function ++and Perl, then this XSUB will be used from Perl with the following code. ++The $status and $timep variables will contain the output of the function. ++ ++ use RPC; ++ $status = rpcb_gettime( "localhost", $timep ); ++ ++The following XS file shows an XS subroutine, or XSUB, which ++demonstrates one possible interface to the rpcb_gettime() ++function. This XSUB represents a direct translation between ++C and Perl and so preserves the interface even from Perl. ++This XSUB will be invoked from Perl with the usage shown ++above. Note that the first three #include statements, for ++C, C, and C, will always be present at the ++beginning of an XS file. This approach and others will be ++expanded later in this document. A #define for C ++should be present to fetch the interpreter context more efficiently, ++see L for details. ++ ++ #define PERL_NO_GET_CONTEXT ++ #include "EXTERN.h" ++ #include "perl.h" ++ #include "XSUB.h" ++ #include ++ ++ MODULE = RPC PACKAGE = RPC ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep ++ OUTPUT: ++ timep ++ ++Any extension to Perl, including those containing XSUBs, ++should have a Perl module to serve as the bootstrap which ++pulls the extension into Perl. This module will export the ++extension's functions and variables to the Perl program and ++will cause the extension's XSUBs to be linked into Perl. ++The following module will be used for most of the examples ++in this document and should be used from Perl with the C ++command as shown earlier. Perl modules are explained in ++more detail later in this document. ++ ++ package RPC; ++ ++ require Exporter; ++ require DynaLoader; ++ @ISA = qw(Exporter DynaLoader); ++ @EXPORT = qw( rpcb_gettime ); ++ ++ bootstrap RPC; ++ 1; ++ ++Throughout this document a variety of interfaces to the rpcb_gettime() ++XSUB will be explored. The XSUBs will take their parameters in different ++orders or will take different numbers of parameters. In each case the ++XSUB is an abstraction between Perl and the real C rpcb_gettime() ++function, and the XSUB must always ensure that the real rpcb_gettime() ++function is called with the correct parameters. This abstraction will ++allow the programmer to create a more Perl-like interface to the C ++function. ++ ++=head2 The Anatomy of an XSUB ++ ++The simplest XSUBs consist of 3 parts: a description of the return ++value, the name of the XSUB routine and the names of its arguments, ++and a description of types or formats of the arguments. ++ ++The following XSUB allows a Perl program to access a C library function ++called sin(). The XSUB will imitate the C function which takes a single ++argument and returns a single value. ++ ++ double ++ sin(x) ++ double x ++ ++Optionally, one can merge the description of types and the list of ++argument names, rewriting this as ++ ++ double ++ sin(double x) ++ ++This makes this XSUB look similar to an ANSI C declaration. An optional ++semicolon is allowed after the argument list, as in ++ ++ double ++ sin(double x); ++ ++Parameters with C pointer types can have different semantic: C functions ++with similar declarations ++ ++ bool string_looks_as_a_number(char *s); ++ bool make_char_uppercase(char *c); ++ ++are used in absolutely incompatible manner. Parameters to these functions ++could be described B like this: ++ ++ char * s ++ char &c ++ ++Both these XS declarations correspond to the C C type, but they have ++different semantics, see L<"The & Unary Operator">. ++ ++It is convenient to think that the indirection operator ++C<*> should be considered as a part of the type and the address operator C<&> ++should be considered part of the variable. See L ++for more info about handling qualifiers and unary operators in C types. ++ ++The function name and the return type must be placed on ++separate lines and should be flush left-adjusted. ++ ++ INCORRECT CORRECT ++ ++ double sin(x) double ++ double x sin(x) ++ double x ++ ++The rest of the function description may be indented or left-adjusted. The ++following example shows a function with its body left-adjusted. Most ++examples in this document will indent the body for better readability. ++ ++ CORRECT ++ ++ double ++ sin(x) ++ double x ++ ++More complicated XSUBs may contain many other sections. Each section of ++an XSUB starts with the corresponding keyword, such as INIT: or CLEANUP:. ++However, the first two lines of an XSUB always contain the same data: ++descriptions of the return type and the names of the function and its ++parameters. Whatever immediately follows these is considered to be ++an INPUT: section unless explicitly marked with another keyword. ++(See L.) ++ ++An XSUB section continues until another section-start keyword is found. ++ ++=head2 The Argument Stack ++ ++The Perl argument stack is used to store the values which are ++sent as parameters to the XSUB and to store the XSUB's ++return value(s). In reality all Perl functions (including non-XSUB ++ones) keep their values on this stack all the same time, each limited ++to its own range of positions on the stack. In this document the ++first position on that stack which belongs to the active ++function will be referred to as position 0 for that function. ++ ++XSUBs refer to their stack arguments with the macro B, where I ++refers to a position in this XSUB's part of the stack. Position 0 for that ++function would be known to the XSUB as ST(0). The XSUB's incoming ++parameters and outgoing return values always begin at ST(0). For many ++simple cases the B compiler will generate the code necessary to ++handle the argument stack by embedding code fragments found in the ++typemaps. In more complex cases the programmer must supply the code. ++ ++=head2 The RETVAL Variable ++ ++The RETVAL variable is a special C variable that is declared automatically ++for you. The C type of RETVAL matches the return type of the C library ++function. The B compiler will declare this variable in each XSUB ++with non-C return type. By default the generated C function ++will use RETVAL to hold the return value of the C library function being ++called. In simple cases the value of RETVAL will be placed in ST(0) of ++the argument stack where it can be received by Perl as the return value ++of the XSUB. ++ ++If the XSUB has a return type of C then the compiler will ++not declare a RETVAL variable for that function. When using ++a PPCODE: section no manipulation of the RETVAL variable is required, the ++section may use direct stack manipulation to place output values on the stack. ++ ++If PPCODE: directive is not used, C return value should be used ++only for subroutines which do not return a value, I CODE: ++directive is used which sets ST(0) explicitly. ++ ++Older versions of this document recommended to use C return ++value in such cases. It was discovered that this could lead to ++segfaults in cases when XSUB was I C. This practice is ++now deprecated, and may be not supported at some future version. Use ++the return value C in such cases. (Currently C contains ++some heuristic code which tries to disambiguate between "truly-void" ++and "old-practice-declared-as-void" functions. Hence your code is at ++mercy of this heuristics unless you use C as return value.) ++ ++=head2 Returning SVs, AVs and HVs through RETVAL ++ ++When you're using RETVAL to return an C, there's some magic ++going on behind the scenes that should be mentioned. When you're ++manipulating the argument stack using the ST(x) macro, for example, ++you usually have to pay special attention to reference counts. (For ++more about reference counts, see L.) To make your life ++easier, the typemap file automatically makes C mortal when ++you're returning an C. Thus, the following two XSUBs are more ++or less equivalent: ++ ++ void ++ alpha() ++ PPCODE: ++ ST(0) = newSVpv("Hello World",0); ++ sv_2mortal(ST(0)); ++ XSRETURN(1); ++ ++ SV * ++ beta() ++ CODE: ++ RETVAL = newSVpv("Hello World",0); ++ OUTPUT: ++ RETVAL ++ ++This is quite useful as it usually improves readability. While ++this works fine for an C, it's unfortunately not as easy ++to have C or C as a return value. You I be ++able to write: ++ ++ AV * ++ array() ++ CODE: ++ RETVAL = newAV(); ++ /* do something with RETVAL */ ++ OUTPUT: ++ RETVAL ++ ++But due to an unfixable bug (fixing it would break lots of existing ++CPAN modules) in the typemap file, the reference count of the C ++is not properly decremented. Thus, the above XSUB would leak memory ++whenever it is being called. The same problem exists for C, ++C, and C (which indicates a scalar reference, not ++a general C). ++In XS code on perls starting with perl 5.16, you can override the ++typemaps for any of these types with a version that has proper ++handling of refcounts. In your C section, do ++ ++ AV* T_AVREF_REFCOUNT_FIXED ++ ++to get the repaired variant. For backward compatibility with older ++versions of perl, you can instead decrement the reference count ++manually when you're returning one of the aforementioned ++types using C: ++ ++ AV * ++ array() ++ CODE: ++ RETVAL = newAV(); ++ sv_2mortal((SV*)RETVAL); ++ /* do something with RETVAL */ ++ OUTPUT: ++ RETVAL ++ ++Remember that you don't have to do this for an C. The reference ++documentation for all core typemaps can be found in L. ++ ++=head2 The MODULE Keyword ++ ++The MODULE keyword is used to start the XS code and to specify the package ++of the functions which are being defined. All text preceding the first ++MODULE keyword is considered C code and is passed through to the output with ++POD stripped, but otherwise untouched. Every XS module will have a ++bootstrap function which is used to hook the XSUBs into Perl. The package ++name of this bootstrap function will match the value of the last MODULE ++statement in the XS source files. The value of MODULE should always remain ++constant within the same XS file, though this is not required. ++ ++The following example will start the XS code and will place ++all functions in a package named RPC. ++ ++ MODULE = RPC ++ ++=head2 The PACKAGE Keyword ++ ++When functions within an XS source file must be separated into packages ++the PACKAGE keyword should be used. This keyword is used with the MODULE ++keyword and must follow immediately after it when used. ++ ++ MODULE = RPC PACKAGE = RPC ++ ++ [ XS code in package RPC ] ++ ++ MODULE = RPC PACKAGE = RPCB ++ ++ [ XS code in package RPCB ] ++ ++ MODULE = RPC PACKAGE = RPC ++ ++ [ XS code in package RPC ] ++ ++The same package name can be used more than once, allowing for ++non-contiguous code. This is useful if you have a stronger ordering ++principle than package names. ++ ++Although this keyword is optional and in some cases provides redundant ++information it should always be used. This keyword will ensure that the ++XSUBs appear in the desired package. ++ ++=head2 The PREFIX Keyword ++ ++The PREFIX keyword designates prefixes which should be ++removed from the Perl function names. If the C function is ++C and the PREFIX value is C then Perl will ++see this function as C. ++ ++This keyword should follow the PACKAGE keyword when used. ++If PACKAGE is not used then PREFIX should follow the MODULE ++keyword. ++ ++ MODULE = RPC PREFIX = rpc_ ++ ++ MODULE = RPC PACKAGE = RPCB PREFIX = rpcb_ ++ ++=head2 The OUTPUT: Keyword ++ ++The OUTPUT: keyword indicates that certain function parameters should be ++updated (new values made visible to Perl) when the XSUB terminates or that ++certain values should be returned to the calling Perl function. For ++simple functions which have no CODE: or PPCODE: section, ++such as the sin() function above, the RETVAL variable is ++automatically designated as an output value. For more complex functions ++the B compiler will need help to determine which variables are output ++variables. ++ ++This keyword will normally be used to complement the CODE: keyword. ++The RETVAL variable is not recognized as an output variable when the ++CODE: keyword is present. The OUTPUT: keyword is used in this ++situation to tell the compiler that RETVAL really is an output ++variable. ++ ++The OUTPUT: keyword can also be used to indicate that function parameters ++are output variables. This may be necessary when a parameter has been ++modified within the function and the programmer would like the update to ++be seen by Perl. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep ++ OUTPUT: ++ timep ++ ++The OUTPUT: keyword will also allow an output parameter to ++be mapped to a matching piece of code rather than to a ++typemap. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep ++ OUTPUT: ++ timep sv_setnv(ST(1), (double)timep); ++ ++B emits an automatic C for all parameters in the ++OUTPUT section of the XSUB, except RETVAL. This is the usually desired ++behavior, as it takes care of properly invoking 'set' magic on output ++parameters (needed for hash or array element parameters that must be ++created if they didn't exist). If for some reason, this behavior is ++not desired, the OUTPUT section may contain a C line ++to disable it for the remainder of the parameters in the OUTPUT section. ++Likewise, C can be used to reenable it for the ++remainder of the OUTPUT section. See L for more details ++about 'set' magic. ++ ++=head2 The NO_OUTPUT Keyword ++ ++The NO_OUTPUT can be placed as the first token of the XSUB. This keyword ++indicates that while the C subroutine we provide an interface to has ++a non-C return type, the return value of this C subroutine should not ++be returned from the generated Perl subroutine. ++ ++With this keyword present L is created, and in the ++generated call to the subroutine this variable is assigned to, but the value ++of this variable is not going to be used in the auto-generated code. ++ ++This keyword makes sense only if C is going to be accessed by the ++user-supplied code. It is especially useful to make a function interface ++more Perl-like, especially when the C return value is just an error condition ++indicator. For example, ++ ++ NO_OUTPUT int ++ delete_file(char *name) ++ POSTCALL: ++ if (RETVAL != 0) ++ croak("Error %d while deleting file '%s'", RETVAL, name); ++ ++Here the generated XS function returns nothing on success, and will die() ++with a meaningful error message on error. ++ ++=head2 The CODE: Keyword ++ ++This keyword is used in more complicated XSUBs which require ++special handling for the C function. The RETVAL variable is ++still declared, but it will not be returned unless it is specified ++in the OUTPUT: section. ++ ++The following XSUB is for a C function which requires special handling of ++its parameters. The Perl usage is given first. ++ ++ $status = rpcb_gettime( "localhost", $timep ); ++ ++The XSUB follows. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t timep ++ CODE: ++ RETVAL = rpcb_gettime( host, &timep ); ++ OUTPUT: ++ timep ++ RETVAL ++ ++=head2 The INIT: Keyword ++ ++The INIT: keyword allows initialization to be inserted into the XSUB before ++the compiler generates the call to the C function. Unlike the CODE: keyword ++above, this keyword does not affect the way the compiler handles RETVAL. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep ++ INIT: ++ printf("# Host is %s\n", host ); ++ OUTPUT: ++ timep ++ ++Another use for the INIT: section is to check for preconditions before ++making a call to the C function: ++ ++ long long ++ lldiv(a,b) ++ long long a ++ long long b ++ INIT: ++ if (a == 0 && b == 0) ++ XSRETURN_UNDEF; ++ if (b == 0) ++ croak("lldiv: cannot divide by 0"); ++ ++=head2 The NO_INIT Keyword ++ ++The NO_INIT keyword is used to indicate that a function ++parameter is being used only as an output value. The B ++compiler will normally generate code to read the values of ++all function parameters from the argument stack and assign ++them to C variables upon entry to the function. NO_INIT ++will tell the compiler that some parameters will be used for ++output rather than for input and that they will be handled ++before the function terminates. ++ ++The following example shows a variation of the rpcb_gettime() function. ++This function uses the timep variable only as an output variable and does ++not care about its initial contents. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep = NO_INIT ++ OUTPUT: ++ timep ++ ++=head2 The TYPEMAP: Keyword ++ ++Starting with Perl 5.16, you can embed typemaps into your XS code ++instead of or in addition to typemaps in a separate file. Multiple ++such embedded typemaps will be processed in order of appearance in ++the XS code and like local typemap files take precedence over the ++default typemap, the embedded typemaps may overwrite previous ++definitions of TYPEMAP, INPUT, and OUTPUT stanzas. The syntax for ++embedded typemaps is ++ ++ TYPEMAP: < keyword must appear in the first column of a ++new line. ++ ++Refer to L for details on writing typemaps. ++ ++=head2 Initializing Function Parameters ++ ++C function parameters are normally initialized with their values from ++the argument stack (which in turn contains the parameters that were ++passed to the XSUB from Perl). The typemaps contain the ++code segments which are used to translate the Perl values to ++the C parameters. The programmer, however, is allowed to ++override the typemaps and supply alternate (or additional) ++initialization code. Initialization code starts with the first ++C<=>, C<;> or C<+> on a line in the INPUT: section. The only ++exception happens if this C<;> terminates the line, then this C<;> ++is quietly ignored. ++ ++The following code demonstrates how to supply initialization code for ++function parameters. The initialization code is eval'ed within double ++quotes by the compiler before it is added to the output so anything ++which should be interpreted literally [mainly C<$>, C<@>, or C<\\>] ++must be protected with backslashes. The variables C<$var>, C<$arg>, ++and C<$type> can be used as in typemaps. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host = (char *)SvPV_nolen($arg); ++ time_t &timep = 0; ++ OUTPUT: ++ timep ++ ++This should not be used to supply default values for parameters. One ++would normally use this when a function parameter must be processed by ++another library function before it can be used. Default parameters are ++covered in the next section. ++ ++If the initialization begins with C<=>, then it is output in ++the declaration for the input variable, replacing the initialization ++supplied by the typemap. If the initialization ++begins with C<;> or C<+>, then it is performed after ++all of the input variables have been declared. In the C<;> ++case the initialization normally supplied by the typemap is not performed. ++For the C<+> case, the declaration for the variable will include the ++initialization from the typemap. A global ++variable, C<%v>, is available for the truly rare case where ++information from one initialization is needed in another ++initialization. ++ ++Here's a truly obscure example: ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ time_t &timep; /* \$v{timep}=@{[$v{timep}=$arg]} */ ++ char *host + SvOK($v{timep}) ? SvPV_nolen($arg) : NULL; ++ OUTPUT: ++ timep ++ ++The construct C<\$v{timep}=@{[$v{timep}=$arg]}> used in the above ++example has a two-fold purpose: first, when this line is processed by ++B, the Perl snippet C<$v{timep}=$arg> is evaluated. Second, ++the text of the evaluated snippet is output into the generated C file ++(inside a C comment)! During the processing of C line, ++C<$arg> will evaluate to C, and C<$v{timep}> will evaluate to ++C. ++ ++=head2 Default Parameter Values ++ ++Default values for XSUB arguments can be specified by placing an ++assignment statement in the parameter list. The default value may ++be a number, a string or the special string C. Defaults should ++always be used on the right-most parameters only. ++ ++To allow the XSUB for rpcb_gettime() to have a default host ++value the parameters to the XSUB could be rearranged. The ++XSUB will then call the real rpcb_gettime() function with ++the parameters in the correct order. This XSUB can be called ++from Perl with either of the following statements: ++ ++ $status = rpcb_gettime( $timep, $host ); ++ ++ $status = rpcb_gettime( $timep ); ++ ++The XSUB will look like the code which follows. A CODE: ++block is used to call the real rpcb_gettime() function with ++the parameters in the correct order for that function. ++ ++ bool_t ++ rpcb_gettime(timep,host="localhost") ++ char *host ++ time_t timep = NO_INIT ++ CODE: ++ RETVAL = rpcb_gettime( host, &timep ); ++ OUTPUT: ++ timep ++ RETVAL ++ ++=head2 The PREINIT: Keyword ++ ++The PREINIT: keyword allows extra variables to be declared immediately ++before or after the declarations of the parameters from the INPUT: section ++are emitted. ++ ++If a variable is declared inside a CODE: section it will follow any typemap ++code that is emitted for the input parameters. This may result in the ++declaration ending up after C code, which is C syntax error. Similar ++errors may happen with an explicit C<;>-type or C<+>-type initialization of ++parameters is used (see L<"Initializing Function Parameters">). Declaring ++these variables in an INIT: section will not help. ++ ++In such cases, to force an additional variable to be declared together ++with declarations of other variables, place the declaration into a ++PREINIT: section. The PREINIT: keyword may be used one or more times ++within an XSUB. ++ ++The following examples are equivalent, but if the code is using complex ++typemaps then the first example is safer. ++ ++ bool_t ++ rpcb_gettime(timep) ++ time_t timep = NO_INIT ++ PREINIT: ++ char *host = "localhost"; ++ CODE: ++ RETVAL = rpcb_gettime( host, &timep ); ++ OUTPUT: ++ timep ++ RETVAL ++ ++For this particular case an INIT: keyword would generate the ++same C code as the PREINIT: keyword. Another correct, but error-prone example: ++ ++ bool_t ++ rpcb_gettime(timep) ++ time_t timep = NO_INIT ++ CODE: ++ char *host = "localhost"; ++ RETVAL = rpcb_gettime( host, &timep ); ++ OUTPUT: ++ timep ++ RETVAL ++ ++Another way to declare C is to use a C block in the CODE: section: ++ ++ bool_t ++ rpcb_gettime(timep) ++ time_t timep = NO_INIT ++ CODE: ++ { ++ char *host = "localhost"; ++ RETVAL = rpcb_gettime( host, &timep ); ++ } ++ OUTPUT: ++ timep ++ RETVAL ++ ++The ability to put additional declarations before the typemap entries are ++processed is very handy in the cases when typemap conversions manipulate ++some global state: ++ ++ MyObject ++ mutate(o) ++ PREINIT: ++ MyState st = global_state; ++ INPUT: ++ MyObject o; ++ CLEANUP: ++ reset_to(global_state, st); ++ ++Here we suppose that conversion to C in the INPUT: section and from ++MyObject when processing RETVAL will modify a global variable C. ++After these conversions are performed, we restore the old value of ++C (to avoid memory leaks, for example). ++ ++There is another way to trade clarity for compactness: INPUT sections allow ++declaration of C variables which do not appear in the parameter list of ++a subroutine. Thus the above code for mutate() can be rewritten as ++ ++ MyObject ++ mutate(o) ++ MyState st = global_state; ++ MyObject o; ++ CLEANUP: ++ reset_to(global_state, st); ++ ++and the code for rpcb_gettime() can be rewritten as ++ ++ bool_t ++ rpcb_gettime(timep) ++ time_t timep = NO_INIT ++ char *host = "localhost"; ++ C_ARGS: ++ host, &timep ++ OUTPUT: ++ timep ++ RETVAL ++ ++=head2 The SCOPE: Keyword ++ ++The SCOPE: keyword allows scoping to be enabled for a particular XSUB. If ++enabled, the XSUB will invoke ENTER and LEAVE automatically. ++ ++To support potentially complex type mappings, if a typemap entry used ++by an XSUB contains a comment like C then scoping will ++be automatically enabled for that XSUB. ++ ++To enable scoping: ++ ++ SCOPE: ENABLE ++ ++To disable scoping: ++ ++ SCOPE: DISABLE ++ ++=head2 The INPUT: Keyword ++ ++The XSUB's parameters are usually evaluated immediately after entering the ++XSUB. The INPUT: keyword can be used to force those parameters to be ++evaluated a little later. The INPUT: keyword can be used multiple times ++within an XSUB and can be used to list one or more input variables. This ++keyword is used with the PREINIT: keyword. ++ ++The following example shows how the input parameter C can be ++evaluated late, after a PREINIT. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ PREINIT: ++ time_t tt; ++ INPUT: ++ time_t timep ++ CODE: ++ RETVAL = rpcb_gettime( host, &tt ); ++ timep = tt; ++ OUTPUT: ++ timep ++ RETVAL ++ ++The next example shows each input parameter evaluated late. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ PREINIT: ++ time_t tt; ++ INPUT: ++ char *host ++ PREINIT: ++ char *h; ++ INPUT: ++ time_t timep ++ CODE: ++ h = host; ++ RETVAL = rpcb_gettime( h, &tt ); ++ timep = tt; ++ OUTPUT: ++ timep ++ RETVAL ++ ++Since INPUT sections allow declaration of C variables which do not appear ++in the parameter list of a subroutine, this may be shortened to: ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ time_t tt; ++ char *host; ++ char *h = host; ++ time_t timep; ++ CODE: ++ RETVAL = rpcb_gettime( h, &tt ); ++ timep = tt; ++ OUTPUT: ++ timep ++ RETVAL ++ ++(We used our knowledge that input conversion for C is a "simple" one, ++thus C is initialized on the declaration line, and our assignment ++C is not performed too early. Otherwise one would need to have the ++assignment C in a CODE: or INIT: section.) ++ ++=head2 The IN/OUTLIST/IN_OUTLIST/OUT/IN_OUT Keywords ++ ++In the list of parameters for an XSUB, one can precede parameter names ++by the C/C/C/C/C keywords. ++C keyword is the default, the other keywords indicate how the Perl ++interface should differ from the C interface. ++ ++Parameters preceded by C/C/C/C ++keywords are considered to be used by the C subroutine I. C/C keywords indicate that the C subroutine ++does not inspect the memory pointed by this parameter, but will write ++through this pointer to provide additional return values. ++ ++Parameters preceded by C keyword do not appear in the usage ++signature of the generated Perl function. ++ ++Parameters preceded by C/C/C I appear as ++parameters to the Perl function. With the exception of ++C-parameters, these parameters are converted to the corresponding ++C type, then pointers to these data are given as arguments to the C ++function. It is expected that the C function will write through these ++pointers. ++ ++The return list of the generated Perl function consists of the C return value ++from the function (unless the XSUB is of C return type or ++C was used) followed by all the C ++and C parameters (in the order of appearance). On the ++return from the XSUB the C/C Perl parameter will be ++modified to have the values written by the C function. ++ ++For example, an XSUB ++ ++ void ++ day_month(OUTLIST day, IN unix_time, OUTLIST month) ++ int day ++ int unix_time ++ int month ++ ++should be used from Perl as ++ ++ my ($day, $month) = day_month(time); ++ ++The C signature of the corresponding function should be ++ ++ void day_month(int *day, int unix_time, int *month); ++ ++The C/C/C/C/C keywords can be ++mixed with ANSI-style declarations, as in ++ ++ void ++ day_month(OUTLIST int day, int unix_time, OUTLIST int month) ++ ++(here the optional C keyword is omitted). ++ ++The C parameters are identical with parameters introduced with ++L and put into the C section (see ++L). The C parameters are very similar, ++the only difference being that the value C function writes through the ++pointer would not modify the Perl parameter, but is put in the output ++list. ++ ++The C/C parameter differ from C/C ++parameters only by the initial value of the Perl parameter not ++being read (and not being given to the C function - which gets some ++garbage instead). For example, the same C function as above can be ++interfaced with as ++ ++ void day_month(OUT int day, int unix_time, OUT int month); ++ ++or ++ ++ void ++ day_month(day, unix_time, month) ++ int &day = NO_INIT ++ int unix_time ++ int &month = NO_INIT ++ OUTPUT: ++ day ++ month ++ ++However, the generated Perl function is called in very C-ish style: ++ ++ my ($day, $month); ++ day_month($day, time, $month); ++ ++=head2 The C Keyword ++ ++If one of the input arguments to the C function is the length of a string ++argument C, one can substitute the name of the length-argument by ++C in the XSUB declaration. This argument must be omitted when ++the generated Perl function is called. E.g., ++ ++ void ++ dump_chars(char *s, short l) ++ { ++ short n = 0; ++ while (n < l) { ++ printf("s[%d] = \"\\%#03o\"\n", n, (int)s[n]); ++ n++; ++ } ++ } ++ ++ MODULE = x PACKAGE = x ++ ++ void dump_chars(char *s, short length(s)) ++ ++should be called as C. ++ ++This directive is supported with ANSI-type function declarations only. ++ ++=head2 Variable-length Parameter Lists ++ ++XSUBs can have variable-length parameter lists by specifying an ellipsis ++C<(...)> in the parameter list. This use of the ellipsis is similar to that ++found in ANSI C. The programmer is able to determine the number of ++arguments passed to the XSUB by examining the C variable which the ++B compiler supplies for all XSUBs. By using this mechanism one can ++create an XSUB which accepts a list of parameters of unknown length. ++ ++The I parameter for the rpcb_gettime() XSUB can be ++optional so the ellipsis can be used to indicate that the ++XSUB will take a variable number of parameters. Perl should ++be able to call this XSUB with either of the following statements. ++ ++ $status = rpcb_gettime( $timep, $host ); ++ ++ $status = rpcb_gettime( $timep ); ++ ++The XS code, with ellipsis, follows. ++ ++ bool_t ++ rpcb_gettime(timep, ...) ++ time_t timep = NO_INIT ++ PREINIT: ++ char *host = "localhost"; ++ CODE: ++ if( items > 1 ) ++ host = (char *)SvPV_nolen(ST(1)); ++ RETVAL = rpcb_gettime( host, &timep ); ++ OUTPUT: ++ timep ++ RETVAL ++ ++=head2 The C_ARGS: Keyword ++ ++The C_ARGS: keyword allows creating of XSUBS which have different ++calling sequence from Perl than from C, without a need to write ++CODE: or PPCODE: section. The contents of the C_ARGS: paragraph is ++put as the argument to the called C function without any change. ++ ++For example, suppose that a C function is declared as ++ ++ symbolic nth_derivative(int n, symbolic function, int flags); ++ ++and that the default flags are kept in a global C variable ++C. Suppose that you want to create an interface which ++is called as ++ ++ $second_deriv = $function->nth_derivative(2); ++ ++To do this, declare the XSUB as ++ ++ symbolic ++ nth_derivative(function, n) ++ symbolic function ++ int n ++ C_ARGS: ++ n, function, default_flags ++ ++=head2 The PPCODE: Keyword ++ ++The PPCODE: keyword is an alternate form of the CODE: keyword and is used ++to tell the B compiler that the programmer is supplying the code to ++control the argument stack for the XSUBs return values. Occasionally one ++will want an XSUB to return a list of values rather than a single value. ++In these cases one must use PPCODE: and then explicitly push the list of ++values on the stack. The PPCODE: and CODE: keywords should not be used ++together within the same XSUB. ++ ++The actual difference between PPCODE: and CODE: sections is in the ++initialization of C macro (which stands for the I Perl ++stack pointer), and in the handling of data on the stack when returning ++from an XSUB. In CODE: sections SP preserves the value which was on ++entry to the XSUB: SP is on the function pointer (which follows the ++last parameter). In PPCODE: sections SP is moved backward to the ++beginning of the parameter list, which allows C macros ++to place output values in the place Perl expects them to be when ++the XSUB returns back to Perl. ++ ++The generated trailer for a CODE: section ensures that the number of return ++values Perl will see is either 0 or 1 (depending on the Cness of the ++return value of the C function, and heuristics mentioned in ++L<"The RETVAL Variable">). The trailer generated for a PPCODE: section ++is based on the number of return values and on the number of times ++C was updated by C<[X]PUSH*()> macros. ++ ++Note that macros C, C and C work equally ++well in CODE: sections and PPCODE: sections. ++ ++The following XSUB will call the C rpcb_gettime() function ++and will return its two output values, timep and status, to ++Perl as a single list. ++ ++ void ++ rpcb_gettime(host) ++ char *host ++ PREINIT: ++ time_t timep; ++ bool_t status; ++ PPCODE: ++ status = rpcb_gettime( host, &timep ); ++ EXTEND(SP, 2); ++ PUSHs(sv_2mortal(newSViv(status))); ++ PUSHs(sv_2mortal(newSViv(timep))); ++ ++Notice that the programmer must supply the C code necessary ++to have the real rpcb_gettime() function called and to have ++the return values properly placed on the argument stack. ++ ++The C return type for this function tells the B compiler that ++the RETVAL variable is not needed or used and that it should not be created. ++In most scenarios the void return type should be used with the PPCODE: ++directive. ++ ++The EXTEND() macro is used to make room on the argument ++stack for 2 return values. The PPCODE: directive causes the ++B compiler to create a stack pointer available as C, and it ++is this pointer which is being used in the EXTEND() macro. ++The values are then pushed onto the stack with the PUSHs() ++macro. ++ ++Now the rpcb_gettime() function can be used from Perl with ++the following statement. ++ ++ ($status, $timep) = rpcb_gettime("localhost"); ++ ++When handling output parameters with a PPCODE section, be sure to handle ++'set' magic properly. See L for details about 'set' magic. ++ ++=head2 Returning Undef And Empty Lists ++ ++Occasionally the programmer will want to return simply ++C or an empty list if a function fails rather than a ++separate status value. The rpcb_gettime() function offers ++just this situation. If the function succeeds we would like ++to have it return the time and if it fails we would like to ++have undef returned. In the following Perl code the value ++of $timep will either be undef or it will be a valid time. ++ ++ $timep = rpcb_gettime( "localhost" ); ++ ++The following XSUB uses the C return type as a mnemonic only, ++and uses a CODE: block to indicate to the compiler ++that the programmer has supplied all the necessary code. The ++sv_newmortal() call will initialize the return value to undef, making that ++the default return value. ++ ++ SV * ++ rpcb_gettime(host) ++ char * host ++ PREINIT: ++ time_t timep; ++ bool_t x; ++ CODE: ++ ST(0) = sv_newmortal(); ++ if( rpcb_gettime( host, &timep ) ) ++ sv_setnv( ST(0), (double)timep); ++ ++The next example demonstrates how one would place an explicit undef in the ++return value, should the need arise. ++ ++ SV * ++ rpcb_gettime(host) ++ char * host ++ PREINIT: ++ time_t timep; ++ bool_t x; ++ CODE: ++ if( rpcb_gettime( host, &timep ) ){ ++ ST(0) = sv_newmortal(); ++ sv_setnv( ST(0), (double)timep); ++ } ++ else{ ++ ST(0) = &PL_sv_undef; ++ } ++ ++To return an empty list one must use a PPCODE: block and ++then not push return values on the stack. ++ ++ void ++ rpcb_gettime(host) ++ char *host ++ PREINIT: ++ time_t timep; ++ PPCODE: ++ if( rpcb_gettime( host, &timep ) ) ++ PUSHs(sv_2mortal(newSViv(timep))); ++ else{ ++ /* Nothing pushed on stack, so an empty ++ * list is implicitly returned. */ ++ } ++ ++Some people may be inclined to include an explicit C in the above ++XSUB, rather than letting control fall through to the end. In those ++situations C should be used, instead. This will ensure that ++the XSUB stack is properly adjusted. Consult L for other ++C macros. ++ ++Since C macros can be used with CODE blocks as well, one can ++rewrite this example as: ++ ++ int ++ rpcb_gettime(host) ++ char *host ++ PREINIT: ++ time_t timep; ++ CODE: ++ RETVAL = rpcb_gettime( host, &timep ); ++ if (RETVAL == 0) ++ XSRETURN_UNDEF; ++ OUTPUT: ++ RETVAL ++ ++In fact, one can put this check into a POSTCALL: section as well. Together ++with PREINIT: simplifications, this leads to: ++ ++ int ++ rpcb_gettime(host) ++ char *host ++ time_t timep; ++ POSTCALL: ++ if (RETVAL == 0) ++ XSRETURN_UNDEF; ++ ++=head2 The REQUIRE: Keyword ++ ++The REQUIRE: keyword is used to indicate the minimum version of the ++B compiler needed to compile the XS module. An XS module which ++contains the following statement will compile with only B version ++1.922 or greater: ++ ++ REQUIRE: 1.922 ++ ++=head2 The CLEANUP: Keyword ++ ++This keyword can be used when an XSUB requires special cleanup procedures ++before it terminates. When the CLEANUP: keyword is used it must follow ++any CODE:, or OUTPUT: blocks which are present in the XSUB. The code ++specified for the cleanup block will be added as the last statements in ++the XSUB. ++ ++=head2 The POSTCALL: Keyword ++ ++This keyword can be used when an XSUB requires special procedures ++executed after the C subroutine call is performed. When the POSTCALL: ++keyword is used it must precede OUTPUT: and CLEANUP: blocks which are ++present in the XSUB. ++ ++See examples in L<"The NO_OUTPUT Keyword"> and L<"Returning Undef And Empty Lists">. ++ ++The POSTCALL: block does not make a lot of sense when the C subroutine ++call is supplied by user by providing either CODE: or PPCODE: section. ++ ++=head2 The BOOT: Keyword ++ ++The BOOT: keyword is used to add code to the extension's bootstrap ++function. The bootstrap function is generated by the B compiler and ++normally holds the statements necessary to register any XSUBs with Perl. ++With the BOOT: keyword the programmer can tell the compiler to add extra ++statements to the bootstrap function. ++ ++This keyword may be used any time after the first MODULE keyword and should ++appear on a line by itself. The first blank line after the keyword will ++terminate the code block. ++ ++ BOOT: ++ # The following message will be printed when the ++ # bootstrap function executes. ++ printf("Hello from the bootstrap!\n"); ++ ++=head2 The VERSIONCHECK: Keyword ++ ++The VERSIONCHECK: keyword corresponds to B's C<-versioncheck> and ++C<-noversioncheck> options. This keyword overrides the command line ++options. Version checking is enabled by default. When version checking is ++enabled the XS module will attempt to verify that its version matches the ++version of the PM module. ++ ++To enable version checking: ++ ++ VERSIONCHECK: ENABLE ++ ++To disable version checking: ++ ++ VERSIONCHECK: DISABLE ++ ++Note that if the version of the PM module is an NV (a floating point ++number), it will be stringified with a possible loss of precision ++(currently chopping to nine decimal places) so that it may not match ++the version of the XS module anymore. Quoting the $VERSION declaration ++to make it a string is recommended if long version numbers are used. ++ ++=head2 The PROTOTYPES: Keyword ++ ++The PROTOTYPES: keyword corresponds to B's C<-prototypes> and ++C<-noprototypes> options. This keyword overrides the command line options. ++Prototypes are disabled by default. When prototypes are enabled, XSUBs will ++be given Perl prototypes. This keyword may be used multiple times in an XS ++module to enable and disable prototypes for different parts of the module. ++Note that B will nag you if you don't explicitly enable or disable ++prototypes, with: ++ ++ Please specify prototyping behavior for Foo.xs (see perlxs manual) ++ ++To enable prototypes: ++ ++ PROTOTYPES: ENABLE ++ ++To disable prototypes: ++ ++ PROTOTYPES: DISABLE ++ ++=head2 The PROTOTYPE: Keyword ++ ++This keyword is similar to the PROTOTYPES: keyword above but can be used to ++force B to use a specific prototype for the XSUB. This keyword ++overrides all other prototype options and keywords but affects only the ++current XSUB. Consult L for information about Perl ++prototypes. ++ ++ bool_t ++ rpcb_gettime(timep, ...) ++ time_t timep = NO_INIT ++ PROTOTYPE: $;$ ++ PREINIT: ++ char *host = "localhost"; ++ CODE: ++ if( items > 1 ) ++ host = (char *)SvPV_nolen(ST(1)); ++ RETVAL = rpcb_gettime( host, &timep ); ++ OUTPUT: ++ timep ++ RETVAL ++ ++If the prototypes are enabled, you can disable it locally for a given ++XSUB as in the following example: ++ ++ void ++ rpcb_gettime_noproto() ++ PROTOTYPE: DISABLE ++ ... ++ ++=head2 The ALIAS: Keyword ++ ++The ALIAS: keyword allows an XSUB to have two or more unique Perl names ++and to know which of those names was used when it was invoked. The Perl ++names may be fully-qualified with package names. Each alias is given an ++index. The compiler will setup a variable called C which contain the ++index of the alias which was used. When the XSUB is called with its ++declared name C will be 0. ++ ++The following example will create aliases C and ++C for this function. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep ++ ALIAS: ++ FOO::gettime = 1 ++ BAR::getit = 2 ++ INIT: ++ printf("# ix = %d\n", ix ); ++ OUTPUT: ++ timep ++ ++=head2 The OVERLOAD: Keyword ++ ++Instead of writing an overloaded interface using pure Perl, you ++can also use the OVERLOAD keyword to define additional Perl names ++for your functions (like the ALIAS: keyword above). However, the ++overloaded functions must be defined in such a way as to accept the number ++of parameters supplied by perl's overload system. For most overload ++methods, it will be three parameters; for the C function it will ++be four. However, the bitwise operators C<&>, C<|>, C<^>, and C<~> may be ++called with three I five arguments (see L). ++ ++If any ++function has the OVERLOAD: keyword, several additional lines ++will be defined in the c file generated by xsubpp in order to ++register with the overload magic. ++ ++Since blessed objects are actually stored as RV's, it is useful ++to use the typemap features to preprocess parameters and extract ++the actual SV stored within the blessed RV. See the sample for ++T_PTROBJ_SPECIAL below. ++ ++To use the OVERLOAD: keyword, create an XS function which takes ++three input parameters (or use the C-style '...' definition) like ++this: ++ ++ SV * ++ cmp (lobj, robj, swap) ++ My_Module_obj lobj ++ My_Module_obj robj ++ IV swap ++ OVERLOAD: cmp <=> ++ { /* function defined here */} ++ ++In this case, the function will overload both of the three way ++comparison operators. For all overload operations using non-alpha ++characters, you must type the parameter without quoting, separating ++multiple overloads with whitespace. Note that "" (the stringify ++overload) should be entered as \"\" (i.e. escaped). ++ ++Since, as mentioned above, bitwise operators may take extra arguments, you ++may want to use something like C<(lobj, robj, swap, ...)> (with ++literal C<...>) as your parameter list. ++ ++=head2 The FALLBACK: Keyword ++ ++In addition to the OVERLOAD keyword, if you need to control how ++Perl autogenerates missing overloaded operators, you can set the ++FALLBACK keyword in the module header section, like this: ++ ++ MODULE = RPC PACKAGE = RPC ++ ++ FALLBACK: TRUE ++ ... ++ ++where FALLBACK can take any of the three values TRUE, FALSE, or ++UNDEF. If you do not set any FALLBACK value when using OVERLOAD, ++it defaults to UNDEF. FALLBACK is not used except when one or ++more functions using OVERLOAD have been defined. Please see ++L for more details. ++ ++=head2 The INTERFACE: Keyword ++ ++This keyword declares the current XSUB as a keeper of the given ++calling signature. If some text follows this keyword, it is ++considered as a list of functions which have this signature, and ++should be attached to the current XSUB. ++ ++For example, if you have 4 C functions multiply(), divide(), add(), ++subtract() all having the signature: ++ ++ symbolic f(symbolic, symbolic); ++ ++you can make them all to use the same XSUB using this: ++ ++ symbolic ++ interface_s_ss(arg1, arg2) ++ symbolic arg1 ++ symbolic arg2 ++ INTERFACE: ++ multiply divide ++ add subtract ++ ++(This is the complete XSUB code for 4 Perl functions!) Four generated ++Perl function share names with corresponding C functions. ++ ++The advantage of this approach comparing to ALIAS: keyword is that there ++is no need to code a switch statement, each Perl function (which shares ++the same XSUB) knows which C function it should call. Additionally, one ++can attach an extra function remainder() at runtime by using ++ ++ CV *mycv = newXSproto("Symbolic::remainder", ++ XS_Symbolic_interface_s_ss, __FILE__, "$$"); ++ XSINTERFACE_FUNC_SET(mycv, remainder); ++ ++say, from another XSUB. (This example supposes that there was no ++INTERFACE_MACRO: section, otherwise one needs to use something else instead of ++C, see the next section.) ++ ++=head2 The INTERFACE_MACRO: Keyword ++ ++This keyword allows one to define an INTERFACE using a different way ++to extract a function pointer from an XSUB. The text which follows ++this keyword should give the name of macros which would extract/set a ++function pointer. The extractor macro is given return type, C, ++and C for this C. The setter macro is given cv, ++and the function pointer. ++ ++The default value is C and C. ++An INTERFACE keyword with an empty list of functions can be omitted if ++INTERFACE_MACRO keyword is used. ++ ++Suppose that in the previous example functions pointers for ++multiply(), divide(), add(), subtract() are kept in a global C array ++C with offsets being C, C, C, ++C. Then one can use ++ ++ #define XSINTERFACE_FUNC_BYOFFSET(ret,cv,f) \ ++ ((XSINTERFACE_CVT_ANON(ret))fp[CvXSUBANY(cv).any_i32]) ++ #define XSINTERFACE_FUNC_BYOFFSET_set(cv,f) \ ++ CvXSUBANY(cv).any_i32 = CAT2( f, _off ) ++ ++in C section, ++ ++ symbolic ++ interface_s_ss(arg1, arg2) ++ symbolic arg1 ++ symbolic arg2 ++ INTERFACE_MACRO: ++ XSINTERFACE_FUNC_BYOFFSET ++ XSINTERFACE_FUNC_BYOFFSET_set ++ INTERFACE: ++ multiply divide ++ add subtract ++ ++in XSUB section. ++ ++=head2 The INCLUDE: Keyword ++ ++This keyword can be used to pull other files into the XS module. The other ++files may have XS code. INCLUDE: can also be used to run a command to ++generate the XS code to be pulled into the module. ++ ++The file F contains our C function: ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep ++ OUTPUT: ++ timep ++ ++The XS module can use INCLUDE: to pull that file into it. ++ ++ INCLUDE: Rpcb1.xsh ++ ++If the parameters to the INCLUDE: keyword are followed by a pipe (C<|>) then ++the compiler will interpret the parameters as a command. This feature is ++mildly deprecated in favour of the C directive, as documented ++below. ++ ++ INCLUDE: cat Rpcb1.xsh | ++ ++Do not use this to run perl: C will run the perl that ++happens to be the first in your path and not necessarily the same perl that is ++used to run C. See L<"The INCLUDE_COMMAND: Keyword">. ++ ++=head2 The INCLUDE_COMMAND: Keyword ++ ++Runs the supplied command and includes its output into the current XS ++document. C assigns special meaning to the C<$^X> token ++in that it runs the same perl interpreter that is running C: ++ ++ INCLUDE_COMMAND: cat Rpcb1.xsh ++ ++ INCLUDE_COMMAND: $^X -e ... ++ ++=head2 The CASE: Keyword ++ ++The CASE: keyword allows an XSUB to have multiple distinct parts with each ++part acting as a virtual XSUB. CASE: is greedy and if it is used then all ++other XS keywords must be contained within a CASE:. This means nothing may ++precede the first CASE: in the XSUB and anything following the last CASE: is ++included in that case. ++ ++A CASE: might switch via a parameter of the XSUB, via the C ALIAS: ++variable (see L<"The ALIAS: Keyword">), or maybe via the C variable ++(see L<"Variable-length Parameter Lists">). The last CASE: becomes the ++B case if it is not associated with a conditional. The following ++example shows CASE switched via C with a function C ++having an alias C. When the function is called as ++C its parameters are the usual C<(char *host, time_t *timep)>, ++but when the function is called as C its parameters are ++reversed, C<(time_t *timep, char *host)>. ++ ++ long ++ rpcb_gettime(a,b) ++ CASE: ix == 1 ++ ALIAS: ++ x_gettime = 1 ++ INPUT: ++ # 'a' is timep, 'b' is host ++ char *b ++ time_t a = NO_INIT ++ CODE: ++ RETVAL = rpcb_gettime( b, &a ); ++ OUTPUT: ++ a ++ RETVAL ++ CASE: ++ # 'a' is host, 'b' is timep ++ char *a ++ time_t &b = NO_INIT ++ OUTPUT: ++ b ++ RETVAL ++ ++That function can be called with either of the following statements. Note ++the different argument lists. ++ ++ $status = rpcb_gettime( $host, $timep ); ++ ++ $status = x_gettime( $timep, $host ); ++ ++=head2 The EXPORT_XSUB_SYMBOLS: Keyword ++ ++The EXPORT_XSUB_SYMBOLS: keyword is likely something you will never need. ++In perl versions earlier than 5.16.0, this keyword does nothing. Starting ++with 5.16, XSUB symbols are no longer exported by default. That is, they ++are C functions. If you include ++ ++ EXPORT_XSUB_SYMBOLS: ENABLE ++ ++in your XS code, the XSUBs following this line will not be declared C. ++You can later disable this with ++ ++ EXPORT_XSUB_SYMBOLS: DISABLE ++ ++which, again, is the default that you should probably never change. ++You cannot use this keyword on versions of perl before 5.16 to make ++XSUBs C. ++ ++=head2 The & Unary Operator ++ ++The C<&> unary operator in the INPUT: section is used to tell B ++that it should convert a Perl value to/from C using the C type to the left ++of C<&>, but provide a pointer to this value when the C function is called. ++ ++This is useful to avoid a CODE: block for a C function which takes a parameter ++by reference. Typically, the parameter should be not a pointer type (an ++C or C but not an C or C). ++ ++The following XSUB will generate incorrect C code. The B compiler will ++turn this into code which calls C with parameters C<(char ++*host, time_t timep)>, but the real C wants the C ++parameter to be of type C rather than C. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t timep ++ OUTPUT: ++ timep ++ ++That problem is corrected by using the C<&> operator. The B compiler ++will now turn this into code which calls C correctly with ++parameters C<(char *host, time_t *timep)>. It does this by carrying the ++C<&> through, so the function call looks like C. ++ ++ bool_t ++ rpcb_gettime(host,timep) ++ char *host ++ time_t &timep ++ OUTPUT: ++ timep ++ ++=head2 Inserting POD, Comments and C Preprocessor Directives ++ ++C preprocessor directives are allowed within BOOT:, PREINIT: INIT:, CODE:, ++PPCODE:, POSTCALL:, and CLEANUP: blocks, as well as outside the functions. ++Comments are allowed anywhere after the MODULE keyword. The compiler will ++pass the preprocessor directives through untouched and will remove the ++commented lines. POD documentation is allowed at any point, both in the ++C and XS language sections. POD must be terminated with a C<=cut> command; ++C will exit with an error if it does not. It is very unlikely that ++human generated C code will be mistaken for POD, as most indenting styles ++result in whitespace in front of any line starting with C<=>. Machine ++generated XS files may fall into this trap unless care is taken to ++ensure that a space breaks the sequence "\n=". ++ ++Comments can be added to XSUBs by placing a C<#> as the first ++non-whitespace of a line. Care should be taken to avoid making the ++comment look like a C preprocessor directive, lest it be interpreted as ++such. The simplest way to prevent this is to put whitespace in front of ++the C<#>. ++ ++If you use preprocessor directives to choose one of two ++versions of a function, use ++ ++ #if ... version1 ++ #else /* ... version2 */ ++ #endif ++ ++and not ++ ++ #if ... version1 ++ #endif ++ #if ... version2 ++ #endif ++ ++because otherwise B will believe that you made a duplicate ++definition of the function. Also, put a blank line before the ++#else/#endif so it will not be seen as part of the function body. ++ ++=head2 Using XS With C++ ++ ++If an XSUB name contains C<::>, it is considered to be a C++ method. ++The generated Perl function will assume that ++its first argument is an object pointer. The object pointer ++will be stored in a variable called THIS. The object should ++have been created by C++ with the new() function and should ++be blessed by Perl with the sv_setref_pv() macro. The ++blessing of the object by Perl can be handled by a typemap. An example ++typemap is shown at the end of this section. ++ ++If the return type of the XSUB includes C, the method is considered ++to be a static method. It will call the C++ ++function using the class::method() syntax. If the method is not static ++the function will be called using the THIS-Emethod() syntax. ++ ++The next examples will use the following C++ class. ++ ++ class color { ++ public: ++ color(); ++ ~color(); ++ int blue(); ++ void set_blue( int ); ++ ++ private: ++ int c_blue; ++ }; ++ ++The XSUBs for the blue() and set_blue() methods are defined with the class ++name but the parameter for the object (THIS, or "self") is implicit and is ++not listed. ++ ++ int ++ color::blue() ++ ++ void ++ color::set_blue( val ) ++ int val ++ ++Both Perl functions will expect an object as the first parameter. In the ++generated C++ code the object is called C, and the method call will ++be performed on this object. So in the C++ code the blue() and set_blue() ++methods will be called as this: ++ ++ RETVAL = THIS->blue(); ++ ++ THIS->set_blue( val ); ++ ++You could also write a single get/set method using an optional argument: ++ ++ int ++ color::blue( val = NO_INIT ) ++ int val ++ PROTOTYPE $;$ ++ CODE: ++ if (items > 1) ++ THIS->set_blue( val ); ++ RETVAL = THIS->blue(); ++ OUTPUT: ++ RETVAL ++ ++If the function's name is B then the C++ C function will be ++called and C will be given as its parameter. The generated C++ code for ++ ++ void ++ color::DESTROY() ++ ++will look like this: ++ ++ color *THIS = ...; // Initialized as in typemap ++ ++ delete THIS; ++ ++If the function's name is B then the C++ C function will be called ++to create a dynamic C++ object. The XSUB will expect the class name, which ++will be kept in a variable called C, to be given as the first ++argument. ++ ++ color * ++ color::new() ++ ++The generated C++ code will call C. ++ ++ RETVAL = new color(); ++ ++The following is an example of a typemap that could be used for this C++ ++example. ++ ++ TYPEMAP ++ color * O_OBJECT ++ ++ OUTPUT ++ # The Perl object is blessed into 'CLASS', which should be a ++ # char* having the name of the package for the blessing. ++ O_OBJECT ++ sv_setref_pv( $arg, CLASS, (void*)$var ); ++ ++ INPUT ++ O_OBJECT ++ if( sv_isobject($arg) && (SvTYPE(SvRV($arg)) == SVt_PVMG) ) ++ $var = ($type)SvIV((SV*)SvRV( $arg )); ++ else{ ++ warn("${Package}::$func_name() -- " . ++ "$var is not a blessed SV reference"); ++ XSRETURN_UNDEF; ++ } ++ ++=head2 Interface Strategy ++ ++When designing an interface between Perl and a C library a straight ++translation from C to XS (such as created by C) is often sufficient. ++However, sometimes the interface will look ++very C-like and occasionally nonintuitive, especially when the C function ++modifies one of its parameters, or returns failure inband (as in "negative ++return values mean failure"). In cases where the programmer wishes to ++create a more Perl-like interface the following strategy may help to ++identify the more critical parts of the interface. ++ ++Identify the C functions with input/output or output parameters. The XSUBs for ++these functions may be able to return lists to Perl. ++ ++Identify the C functions which use some inband info as an indication ++of failure. They may be ++candidates to return undef or an empty list in case of failure. If the ++failure may be detected without a call to the C function, you may want to use ++an INIT: section to report the failure. For failures detectable after the C ++function returns one may want to use a POSTCALL: section to process the ++failure. In more complicated cases use CODE: or PPCODE: sections. ++ ++If many functions use the same failure indication based on the return value, ++you may want to create a special typedef to handle this situation. Put ++ ++ typedef int negative_is_failure; ++ ++near the beginning of XS file, and create an OUTPUT typemap entry ++for C which converts negative values to C, or ++maybe croak()s. After this the return value of type C ++will create more Perl-like interface. ++ ++Identify which values are used by only the C and XSUB functions ++themselves, say, when a parameter to a function should be a contents of a ++global variable. If Perl does not need to access the contents of the value ++then it may not be necessary to provide a translation for that value ++from C to Perl. ++ ++Identify the pointers in the C function parameter lists and return ++values. Some pointers may be used to implement input/output or ++output parameters, they can be handled in XS with the C<&> unary operator, ++and, possibly, using the NO_INIT keyword. ++Some others will require handling of types like C, and one needs ++to decide what a useful Perl translation will do in such a case. When ++the semantic is clear, it is advisable to put the translation into a typemap ++file. ++ ++Identify the structures used by the C functions. In many ++cases it may be helpful to use the T_PTROBJ typemap for ++these structures so they can be manipulated by Perl as ++blessed objects. (This is handled automatically by C.) ++ ++If the same C type is used in several different contexts which require ++different translations, C several new types mapped to this C type, ++and create separate F entries for these new types. Use these ++types in declarations of return type and parameters to XSUBs. ++ ++=head2 Perl Objects And C Structures ++ ++When dealing with C structures one should select either ++B or B for the XS type. Both types are ++designed to handle pointers to complex objects. The ++T_PTRREF type will allow the Perl object to be unblessed ++while the T_PTROBJ type requires that the object be blessed. ++By using T_PTROBJ one can achieve a form of type-checking ++because the XSUB will attempt to verify that the Perl object ++is of the expected type. ++ ++The following XS code shows the getnetconfigent() function which is used ++with ONC+ TIRPC. The getnetconfigent() function will return a pointer to a ++C structure and has the C prototype shown below. The example will ++demonstrate how the C pointer will become a Perl reference. Perl will ++consider this reference to be a pointer to a blessed object and will ++attempt to call a destructor for the object. A destructor will be ++provided in the XS source to free the memory used by getnetconfigent(). ++Destructors in XS can be created by specifying an XSUB function whose name ++ends with the word B. XS destructors can be used to free memory ++which may have been malloc'd by another XSUB. ++ ++ struct netconfig *getnetconfigent(const char *netid); ++ ++A C will be created for C. The Perl ++object will be blessed in a class matching the name of the C ++type, with the tag C appended, and the name should not ++have embedded spaces if it will be a Perl package name. The ++destructor will be placed in a class corresponding to the ++class of the object and the PREFIX keyword will be used to ++trim the name to the word DESTROY as Perl will expect. ++ ++ typedef struct netconfig Netconfig; ++ ++ MODULE = RPC PACKAGE = RPC ++ ++ Netconfig * ++ getnetconfigent(netid) ++ char *netid ++ ++ MODULE = RPC PACKAGE = NetconfigPtr PREFIX = rpcb_ ++ ++ void ++ rpcb_DESTROY(netconf) ++ Netconfig *netconf ++ CODE: ++ printf("Now in NetconfigPtr::DESTROY\n"); ++ free( netconf ); ++ ++This example requires the following typemap entry. Consult ++L for more information about adding new typemaps ++for an extension. ++ ++ TYPEMAP ++ Netconfig * T_PTROBJ ++ ++This example will be used with the following Perl statements. ++ ++ use RPC; ++ $netconf = getnetconfigent("udp"); ++ ++When Perl destroys the object referenced by $netconf it will send the ++object to the supplied XSUB DESTROY function. Perl cannot determine, and ++does not care, that this object is a C struct and not a Perl object. In ++this sense, there is no difference between the object created by the ++getnetconfigent() XSUB and an object created by a normal Perl subroutine. ++ ++=head2 Safely Storing Static Data in XS ++ ++Starting with Perl 5.8, a macro framework has been defined to allow ++static data to be safely stored in XS modules that will be accessed from ++a multi-threaded Perl. ++ ++Although primarily designed for use with multi-threaded Perl, the macros ++have been designed so that they will work with non-threaded Perl as well. ++ ++It is therefore strongly recommended that these macros be used by all ++XS modules that make use of static data. ++ ++The easiest way to get a template set of macros to use is by specifying ++the C<-g> (C<--global>) option with h2xs (see L). ++ ++Below is an example module that makes use of the macros. ++ ++ #define PERL_NO_GET_CONTEXT ++ #include "EXTERN.h" ++ #include "perl.h" ++ #include "XSUB.h" ++ ++ /* Global Data */ ++ ++ #define MY_CXT_KEY "BlindMice::_guts" XS_VERSION ++ ++ typedef struct { ++ int count; ++ char name[3][100]; ++ } my_cxt_t; ++ ++ START_MY_CXT ++ ++ MODULE = BlindMice PACKAGE = BlindMice ++ ++ BOOT: ++ { ++ MY_CXT_INIT; ++ MY_CXT.count = 0; ++ strcpy(MY_CXT.name[0], "None"); ++ strcpy(MY_CXT.name[1], "None"); ++ strcpy(MY_CXT.name[2], "None"); ++ } ++ ++ int ++ newMouse(char * name) ++ PREINIT: ++ dMY_CXT; ++ CODE: ++ if (MY_CXT.count >= 3) { ++ warn("Already have 3 blind mice"); ++ RETVAL = 0; ++ } ++ else { ++ RETVAL = ++ MY_CXT.count; ++ strcpy(MY_CXT.name[MY_CXT.count - 1], name); ++ } ++ OUTPUT: ++ RETVAL ++ ++ char * ++ get_mouse_name(index) ++ int index ++ PREINIT: ++ dMY_CXT; ++ CODE: ++ if (index > MY_CXT.count) ++ croak("There are only 3 blind mice."); ++ else ++ RETVAL = MY_CXT.name[index - 1]; ++ OUTPUT: ++ RETVAL ++ ++ void ++ CLONE(...) ++ CODE: ++ MY_CXT_CLONE; ++ ++=head3 MY_CXT REFERENCE ++ ++=over 5 ++ ++=item MY_CXT_KEY ++ ++This macro is used to define a unique key to refer to the static data ++for an XS module. The suggested naming scheme, as used by h2xs, is to ++use a string that consists of the module name, the string "::_guts" ++and the module version number. ++ ++ #define MY_CXT_KEY "MyModule::_guts" XS_VERSION ++ ++=item typedef my_cxt_t ++ ++This struct typedef I always be called C. The other ++C macros assume the existence of the C typedef name. ++ ++Declare a typedef named C that is a structure that contains ++all the data that needs to be interpreter-local. ++ ++ typedef struct { ++ int some_value; ++ } my_cxt_t; ++ ++=item START_MY_CXT ++ ++Always place the START_MY_CXT macro directly after the declaration ++of C. ++ ++=item MY_CXT_INIT ++ ++The MY_CXT_INIT macro initializes storage for the C struct. ++ ++It I be called exactly once, typically in a BOOT: section. If you ++are maintaining multiple interpreters, it should be called once in each ++interpreter instance, except for interpreters cloned from existing ones. ++(But see L below.) ++ ++=item dMY_CXT ++ ++Use the dMY_CXT macro (a declaration) in all the functions that access ++MY_CXT. ++ ++=item MY_CXT ++ ++Use the MY_CXT macro to access members of the C struct. For ++example, if C is ++ ++ typedef struct { ++ int index; ++ } my_cxt_t; ++ ++then use this to access the C member ++ ++ dMY_CXT; ++ MY_CXT.index = 2; ++ ++=item aMY_CXT/pMY_CXT ++ ++C may be quite expensive to calculate, and to avoid the overhead ++of invoking it in each function it is possible to pass the declaration ++onto other functions using the C/C macros, eg ++ ++ void sub1() { ++ dMY_CXT; ++ MY_CXT.index = 1; ++ sub2(aMY_CXT); ++ } ++ ++ void sub2(pMY_CXT) { ++ MY_CXT.index = 2; ++ } ++ ++Analogously to C, there are equivalent forms for when the macro is the ++first or last in multiple arguments, where an underscore represents a ++comma, i.e. C<_aMY_CXT>, C, C<_pMY_CXT> and C. ++ ++=item MY_CXT_CLONE ++ ++By default, when a new interpreter is created as a copy of an existing one ++(eg via C<< threads->create() >>), both interpreters share the same physical ++my_cxt_t structure. Calling C (typically via the package's ++C function), causes a byte-for-byte copy of the structure to be ++taken, and any future dMY_CXT will cause the copy to be accessed instead. ++ ++=item MY_CXT_INIT_INTERP(my_perl) ++ ++=item dMY_CXT_INTERP(my_perl) ++ ++These are versions of the macros which take an explicit interpreter as an ++argument. ++ ++=back ++ ++Note that these macros will only work together within the I source ++file; that is, a dMY_CTX in one source file will access a different structure ++than a dMY_CTX in another source file. ++ ++=head2 Thread-aware system interfaces ++ ++Starting from Perl 5.8, in C/C++ level Perl knows how to wrap ++system/library interfaces that have thread-aware versions ++(e.g. getpwent_r()) into frontend macros (e.g. getpwent()) that ++correctly handle the multithreaded interaction with the Perl ++interpreter. This will happen transparently, the only thing ++you need to do is to instantiate a Perl interpreter. ++ ++This wrapping happens always when compiling Perl core source ++(PERL_CORE is defined) or the Perl core extensions (PERL_EXT is ++defined). When compiling XS code outside of the Perl core, the wrapping ++does not take place before Perl 5.28. Starting in that release you can ++ ++ #define PERL_REENTRANT ++ ++in your code to enable the wrapping. It is advisable to do so if you ++are using such functions, as intermixing the C<_r>-forms (as Perl compiled ++for multithreaded operation will do) and the C<_r>-less forms is neither ++well-defined (inconsistent results, data corruption, or even crashes ++become more likely), nor is it very portable. Unfortunately, not all ++systems have all the C<_r> forms, but using this C<#define> gives you ++whatever protection that Perl is aware is available on each system. ++ ++=head1 EXAMPLES ++ ++File C: Interface to some ONC+ RPC bind library functions. ++ ++ #define PERL_NO_GET_CONTEXT ++ #include "EXTERN.h" ++ #include "perl.h" ++ #include "XSUB.h" ++ ++ #include ++ ++ typedef struct netconfig Netconfig; ++ ++ MODULE = RPC PACKAGE = RPC ++ ++ SV * ++ rpcb_gettime(host="localhost") ++ char *host ++ PREINIT: ++ time_t timep; ++ CODE: ++ ST(0) = sv_newmortal(); ++ if( rpcb_gettime( host, &timep ) ) ++ sv_setnv( ST(0), (double)timep ); ++ ++ Netconfig * ++ getnetconfigent(netid="udp") ++ char *netid ++ ++ MODULE = RPC PACKAGE = NetconfigPtr PREFIX = rpcb_ ++ ++ void ++ rpcb_DESTROY(netconf) ++ Netconfig *netconf ++ CODE: ++ printf("NetconfigPtr::DESTROY\n"); ++ free( netconf ); ++ ++File C: Custom typemap for RPC.xs. (cf. L) ++ ++ TYPEMAP ++ Netconfig * T_PTROBJ ++ ++File C: Perl module for the RPC extension. ++ ++ package RPC; ++ ++ require Exporter; ++ require DynaLoader; ++ @ISA = qw(Exporter DynaLoader); ++ @EXPORT = qw(rpcb_gettime getnetconfigent); ++ ++ bootstrap RPC; ++ 1; ++ ++File C: Perl test program for the RPC extension. ++ ++ use RPC; ++ ++ $netconf = getnetconfigent(); ++ $a = rpcb_gettime(); ++ print "time = $a\n"; ++ print "netconf = $netconf\n"; ++ ++ $netconf = getnetconfigent("tcp"); ++ $a = rpcb_gettime("poplar"); ++ print "time = $a\n"; ++ print "netconf = $netconf\n"; ++ ++=head1 CAVEATS ++ ++XS code has full access to system calls including C library functions. ++It thus has the capability of interfering with things that the Perl core ++or other modules have set up, such as signal handlers or file handles. ++It could mess with the memory, or any number of harmful things. Don't. ++ ++Some modules have an event loop, waiting for user-input. It is highly ++unlikely that two such modules would work adequately together in a ++single Perl application. ++ ++In general, the perl interpreter views itself as the center of the ++universe as far as the Perl program goes. XS code is viewed as a ++help-mate, to accomplish things that perl doesn't do, or doesn't do fast ++enough, but always subservient to perl. The closer XS code adheres to ++this model, the less likely conflicts will occur. ++ ++One area where there has been conflict is in regards to C locales. (See ++L.) perl, with one exception and unless told otherwise, ++sets up the underlying locale the program is running in to the locale ++passed ++into it from the environment. This is an important difference from a ++generic C language program, where the underlying locale is the "C" ++locale unless the program changes it. As of v5.20, this underlying ++locale is completely hidden from pure Perl code outside the lexical ++scope of C> except for a couple of function calls in the ++POSIX module which of necessity use it. But the underlying locale, with ++that ++one exception is exposed to XS code, affecting all C library routines ++whose behavior is locale-dependent. Your XS code better not assume that ++the underlying locale is "C". The exception is the ++L|perllocale/Category LC_NUMERIC: Numeric Formatting> ++locale category, and the reason it is an exception is that experience ++has shown that it can be problematic for XS code, whereas we have not ++had reports of problems with the ++L. And the reason ++for this one category being problematic is that the character used as a ++decimal point can vary. Many European languages use a comma, whereas ++English, and hence Perl are expecting a dot (U+002E: FULL STOP). Many ++modules can handle only the radix character being a dot, and so perl ++attempts to make it so. Up through Perl v5.20, the attempt was merely ++to set C upon startup to the C<"C"> locale. Any ++L otherwise would change ++it; this caused some failures. Therefore, starting in v5.22, perl tries ++to keep C always set to C<"C"> for XS code. ++ ++To summarize, here's what to expect and how to handle locales in XS code: ++ ++=over ++ ++=item Non-locale-aware XS code ++ ++Keep in mind that even if you think your code is not locale-aware, it ++may call a library function that is. Hopefully the man page for such ++a function will indicate that dependency, but the documentation is ++imperfect. ++ ++The current locale is exposed to XS code except possibly C ++(explained in the next paragraph). ++There have not been reports of problems with the other categories. ++Perl initializes things on start-up so that the current locale is the ++one which is indicated by the user's environment in effect at that time. ++See L. ++ ++However, up through v5.20, Perl initialized things on start-up so that ++C was set to the "C" locale. But if any code anywhere ++changed it, it would stay changed. This means that your module can't ++count on C being something in particular, and you can't ++expect floating point numbers (including version strings) to have dots ++in them. If you don't allow for a non-dot, your code could break if ++anyone anywhere changed the locale. For this reason, v5.22 changed ++the behavior so that Perl tries to keep C in the "C" locale ++except around the operations internally where it should be something ++else. Misbehaving XS code will always be able to change the locale ++anyway, but the most common instance of this is checked for and ++handled. ++ ++=item Locale-aware XS code ++ ++If the locale from the user's environment is desired, there should be no ++need for XS code to set the locale except for C, as perl has ++already set the others up. XS code should avoid changing the locale, as ++it can adversely affect other, unrelated, code and may not be ++thread-safe. To minimize problems, the macros ++L, ++L, and ++L should be used to affect any needed ++change. ++ ++But, starting with Perl v5.28, locales are thread-safe on platforms that ++support this functionality. Windows has this starting with Visual ++Studio 2005. Many other modern platforms support the thread-safe POSIX ++2008 functions. The C C<#define> C will be ++defined iff this build is using these. From Perl-space, the read-only ++variable C<${SAFE_LOCALES}> is 1 if either the build is not threaded, or ++if C is defined; otherwise it is 0. ++ ++The way this works under-the-hood is that every thread has a choice of ++using a locale specific to it (this is the Windows and POSIX 2008 ++functionality), or the global locale that is accessible to all threads ++(this is the functionality that has always been there). The ++implementations for Windows and POSIX are completely different. On ++Windows, the runtime can be set up so that the standard ++L> function either only knows about the global locale or ++the locale for this thread. On POSIX, C always deals with ++the global locale, and other functions have been created to handle ++per-thread locales. Perl makes this transparent to perl-space code. It ++continues to use C, and the interpreter translates ++that into the per-thread functions. ++ ++All other locale-senstive functions automatically use the per-thread ++locale, if that is turned on, and failing that, the global locale. Thus ++calls to C are ineffective on POSIX systems for the current ++thread if that thread is using a per-thread locale. If perl is compiled ++for single-thread operation, it does not use the per-thread functions, ++so C does work as expected. ++ ++If you have loaded the L> module you can use the methods given ++in L to call L|POSIX/setlocale> to safely ++change or query the locale (on systems where it is safe to do so), or ++you can use the new 5.28 function L instead, ++which is a drop-in replacement for the system L>, and ++handles single-threaded and multi-threaded applications transparently. ++ ++There are some locale-related library calls that still aren't ++thread-safe because they return data in a buffer global to all threads. ++In the past, these didn't matter as locales weren't thread-safe at all. ++But now you have to be aware of them in case your module is called in a ++multi-threaded application. The known ones are ++ ++ asctime() ++ ctime() ++ gcvt() [POSIX.1-2001 only (function removed in POSIX.1-2008)] ++ getdate() ++ wcrtomb() if its final argument is NULL ++ wcsrtombs() if its final argument is NULL ++ wcstombs() ++ wctomb() ++ ++Some of these shouldn't really be called in a Perl application, and for ++others there are thread-safe versions of these already implemented: ++ ++ asctime_r() ++ ctime_r() ++ Perl_langinfo() ++ ++The C<_r> forms are automatically used, starting in Perl 5.28, if you ++compile your code, with ++ ++ #define PERL_REENTRANT ++ ++See also L. ++You can use the methods given in L, to get the best available ++locale-safe versions of these ++ ++ POSIX::localeconv() ++ POSIX::wcstombs() ++ POSIX::wctomb() ++ ++And note, that some items returned by C are available ++through L. ++ ++The others shouldn't be used in a threaded application. ++ ++Some modules may call a non-perl library that is locale-aware. This is ++fine as long as it doesn't try to query or change the locale using the ++system C. But if these do call the system C, ++those calls may be ineffective. Instead, ++L|perlapi/Perl_setlocale> works in all circumstances. ++Plain setlocale is ineffective on multi-threaded POSIX 2008 systems. It ++operates only on the global locale, whereas each thread has its own ++locale, paying no attention to the global one. Since converting ++these non-Perl libraries to C is out of the question, ++there is a new function in v5.28 ++L|perlapi/switch_to_global_locale> that will ++switch the thread it is called from so that any system C ++calls will have their desired effect. The function ++L|perlapi/sync_locale> must be called before returning to ++perl. ++ ++This thread can change the locale all it wants and it won't affect any ++other thread, except any that also have been switched to the global ++locale. This means that a multi-threaded application can have a single ++thread using an alien library without a problem; but no more than a ++single thread can be so-occupied. Bad results likely will happen. ++ ++In perls without multi-thread locale support, some alien libraries, ++such as C change locales. This can cause problems for the Perl ++core and other modules. For these, before control is returned to ++perl, starting in v5.20.1, calling the function ++L from XS should be sufficient to ++avoid most of these problems. Prior to this, you need a pure Perl ++statement that does this: ++ ++ POSIX::setlocale(LC_ALL, POSIX::setlocale(LC_ALL)); ++ ++or use the methods given in L. ++ ++=back ++ ++=head1 XS VERSION ++ ++This document covers features supported by C ++(also known as C) 3.13_01. ++ ++=head1 AUTHOR ++ ++Originally written by Dean Roehrich >. ++ ++Maintained since 1996 by The Perl Porters >. +diff --git a/lib/perlxstut.pod b/lib/perlxstut.pod +new file mode 100644 +index 0000000..ef154ad +--- /dev/null ++++ b/lib/perlxstut.pod +@@ -0,0 +1,1401 @@ ++=head1 NAME ++ ++perlxstut - Tutorial for writing XSUBs ++ ++=head1 DESCRIPTION ++ ++This tutorial will educate the reader on the steps involved in creating ++a Perl extension. The reader is assumed to have access to L, ++L and L. ++ ++This tutorial starts with very simple examples and becomes more complex, ++with each new example adding new features. Certain concepts may not be ++completely explained until later in the tutorial in order to slowly ease ++the reader into building extensions. ++ ++This tutorial was written from a Unix point of view. Where I know them ++to be otherwise different for other platforms (e.g. Win32), I will list ++them. If you find something that was missed, please let me know. ++ ++=head1 SPECIAL NOTES ++ ++=head2 make ++ ++This tutorial assumes that the make program that Perl is configured to ++use is called C. Instead of running "make" in the examples that ++follow, you may have to substitute whatever make program Perl has been ++configured to use. Running B should tell you what it is. ++ ++=head2 Version caveat ++ ++When writing a Perl extension for general consumption, one should expect that ++the extension will be used with versions of Perl different from the ++version available on your machine. Since you are reading this document, ++the version of Perl on your machine is probably 5.005 or later, but the users ++of your extension may have more ancient versions. ++ ++To understand what kinds of incompatibilities one may expect, and in the rare ++case that the version of Perl on your machine is older than this document, ++see the section on "Troubleshooting these Examples" for more information. ++ ++If your extension uses some features of Perl which are not available on older ++releases of Perl, your users would appreciate an early meaningful warning. ++You would probably put this information into the F file, but nowadays ++installation of extensions may be performed automatically, guided by F ++module or other tools. ++ ++In MakeMaker-based installations, F provides the earliest ++opportunity to perform version checks. One can put something like this ++in F for this purpose: ++ ++ eval { require 5.007 } ++ or die < build them, but you must link the XSUBs subroutines with the ++rest of Perl, creating a new executable. This situation is similar to ++Perl 4. ++ ++This tutorial can still be used on such a system. The XSUB build mechanism ++will check the system and build a dynamically-loadable library if possible, ++or else a static library and then, optionally, a new statically-linked ++executable with that static library linked in. ++ ++Should you wish to build a statically-linked executable on a system which ++can dynamically load libraries, you may, in all the following examples, ++where the command "C" with no arguments is executed, run the command ++"C" instead. ++ ++If you have generated such a statically-linked executable by choice, then ++instead of saying "C", you should say "C". ++On systems that cannot build dynamically-loadable libraries at all, simply ++saying "C" is sufficient. ++ ++=head2 Threads and PERL_NO_GET_CONTEXT ++ ++For threaded builds, perl requires the context pointer for the current ++thread, without C, perl will call a function to ++retrieve the context. ++ ++For improved performance, include: ++ ++ #define PERL_NO_GET_CONTEXT ++ ++as shown below. ++ ++For more details, see L. ++ ++=head1 TUTORIAL ++ ++Now let's go on with the show! ++ ++=head2 EXAMPLE 1 ++ ++Our first extension will be very simple. When we call the routine in the ++extension, it will print out a well-known message and return. ++ ++Run "C". This creates a directory named Mytest, ++possibly under ext/ if that directory exists in the current working ++directory. Several files will be created under the Mytest dir, including ++MANIFEST, Makefile.PL, lib/Mytest.pm, Mytest.xs, t/Mytest.t, and Changes. ++ ++The MANIFEST file contains the names of all the files just created in the ++Mytest directory. ++ ++The file Makefile.PL should look something like this: ++ ++ use ExtUtils::MakeMaker; ++ # See lib/ExtUtils/MakeMaker.pm for details of how to influence ++ # the contents of the Makefile that is written. ++ WriteMakefile( ++ NAME => 'Mytest', ++ VERSION_FROM => 'Mytest.pm', # finds $VERSION ++ LIBS => [''], # e.g., '-lm' ++ DEFINE => '', # e.g., '-DHAVE_SOMETHING' ++ INC => '', # e.g., '-I/usr/include/other' ++ ); ++ ++The file Mytest.pm should start with something like this: ++ ++ package Mytest; ++ ++ use 5.008008; ++ use strict; ++ use warnings; ++ ++ require Exporter; ++ ++ our @ISA = qw(Exporter); ++ our %EXPORT_TAGS = ( 'all' => [ qw( ++ ++ ) ] ); ++ ++ our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } ); ++ ++ our @EXPORT = qw( ++ ++ ); ++ ++ our $VERSION = '0.01'; ++ ++ require XSLoader; ++ XSLoader::load('Mytest', $VERSION); ++ ++ # Preloaded methods go here. ++ ++ 1; ++ __END__ ++ # Below is the stub of documentation for your module. You better ++ # edit it! ++ ++The rest of the .pm file contains sample code for providing documentation for ++the extension. ++ ++Finally, the Mytest.xs file should look something like this: ++ ++ #define PERL_NO_GET_CONTEXT ++ #include "EXTERN.h" ++ #include "perl.h" ++ #include "XSUB.h" ++ ++ #include "ppport.h" ++ ++ MODULE = Mytest PACKAGE = Mytest ++ ++Let's edit the .xs file by adding this to the end of the file: ++ ++ void ++ hello() ++ CODE: ++ printf("Hello, world!\n"); ++ ++It is okay for the lines starting at the "CODE:" line to not be indented. ++However, for readability purposes, it is suggested that you indent CODE: ++one level and the lines following one more level. ++ ++Now we'll run "C". This will create a real Makefile, ++which make needs. Its output looks something like: ++ ++ % perl Makefile.PL ++ Checking if your kit is complete... ++ Looks good ++ Writing Makefile for Mytest ++ % ++ ++Now, running make will produce output that looks something like this (some ++long lines have been shortened for clarity and some extraneous lines have ++been deleted): ++ ++ % make ++ cp lib/Mytest.pm blib/lib/Mytest.pm ++ perl xsubpp -typemap typemap Mytest.xs > Mytest.xsc && \ ++ mv Mytest.xsc Mytest.c ++ Please specify prototyping behavior for Mytest.xs (see perlxs manual) ++ cc -c Mytest.c ++ Running Mkbootstrap for Mytest () ++ chmod 644 Mytest.bs ++ rm -f blib/arch/auto/Mytest/Mytest.so ++ cc -shared -L/usr/local/lib Mytest.o -o blib/arch/auto/Mytest/Mytest.so ++ ++ chmod 755 blib/arch/auto/Mytest/Mytest.so ++ cp Mytest.bs blib/arch/auto/Mytest/Mytest.bs ++ chmod 644 blib/arch/auto/Mytest/Mytest.bs ++ Manifying blib/man3/Mytest.3pm ++ % ++ ++You can safely ignore the line about "prototyping behavior" - it is ++explained in L. ++ ++Perl has its own special way of easily writing test scripts, but for this ++example only, we'll create our own test script. Create a file called hello ++that looks like this: ++ ++ #! /opt/perl5/bin/perl ++ ++ use ExtUtils::testlib; ++ ++ use Mytest; ++ ++ Mytest::hello(); ++ ++Now we make the script executable (C), run the script ++and we should see the following output: ++ ++ % ./hello ++ Hello, world! ++ % ++ ++=head2 EXAMPLE 2 ++ ++Now let's add to our extension a subroutine that will take a single numeric ++argument as input and return 1 if the number is even or 0 if the number ++is odd. ++ ++Add the following to the end of Mytest.xs: ++ ++ int ++ is_even(input) ++ int input ++ CODE: ++ RETVAL = (input % 2 == 0); ++ OUTPUT: ++ RETVAL ++ ++There does not need to be whitespace at the start of the "C" ++line, but it is useful for improving readability. Placing a semi-colon at ++the end of that line is also optional. Any amount and kind of whitespace ++may be placed between the "C" and "C". ++ ++Now re-run make to rebuild our new shared library. ++ ++Now perform the same steps as before, generating a Makefile from the ++Makefile.PL file, and running make. ++ ++In order to test that our extension works, we now need to look at the ++file Mytest.t. This file is set up to imitate the same kind of testing ++structure that Perl itself has. Within the test script, you perform a ++number of tests to confirm the behavior of the extension, printing "ok" ++when the test is correct, "not ok" when it is not. ++ ++ use Test::More tests => 4; ++ BEGIN { use_ok('Mytest') }; ++ ++ ######################### ++ ++ # Insert your test code below, the Test::More module is use()ed here ++ # so read its man page ( perldoc Test::More ) for help writing this ++ # test script. ++ ++ is(&Mytest::is_even(0), 1); ++ is(&Mytest::is_even(1), 0); ++ is(&Mytest::is_even(2), 1); ++ ++We will be calling the test script through the command "C". You ++should see output that looks something like this: ++ ++ %make test ++ PERL_DL_NONLAZY=1 /usr/bin/perl "-MExtUtils::Command::MM" "-e" ++ "test_harness(0, 'blib/lib', 'blib/arch')" t/*.t ++ t/Mytest....ok ++ All tests successful. ++ Files=1, Tests=4, 0 wallclock secs ( 0.03 cusr + 0.00 csys = 0.03 CPU) ++ % ++ ++=head2 What has gone on? ++ ++The program h2xs is the starting point for creating extensions. In later ++examples we'll see how we can use h2xs to read header files and generate ++templates to connect to C routines. ++ ++h2xs creates a number of files in the extension directory. The file ++Makefile.PL is a perl script which will generate a true Makefile to build ++the extension. We'll take a closer look at it later. ++ ++The .pm and .xs files contain the meat of the extension. The .xs file holds ++the C routines that make up the extension. The .pm file contains routines ++that tell Perl how to load your extension. ++ ++Generating the Makefile and running C created a directory called blib ++(which stands for "build library") in the current working directory. This ++directory will contain the shared library that we will build. Once we have ++tested it, we can install it into its final location. ++ ++Invoking the test script via "C" did something very important. ++It invoked perl with all those C<-I> arguments so that it could find the ++various files that are part of the extension. It is I important that ++while you are still testing extensions that you use "C". If you ++try to run the test script all by itself, you will get a fatal error. ++Another reason it is important to use "C" to run your test ++script is that if you are testing an upgrade to an already-existing version, ++using "C" ensures that you will test your new extension, not the ++already-existing version. ++ ++When Perl sees a C, it searches for a file with the same name ++as the C'd extension that has a .pm suffix. If that file cannot be found, ++Perl dies with a fatal error. The default search path is contained in the ++C<@INC> array. ++ ++In our case, Mytest.pm tells perl that it will need the Exporter and Dynamic ++Loader extensions. It then sets the C<@ISA> and C<@EXPORT> arrays and the ++C<$VERSION> scalar; finally it tells perl to bootstrap the module. Perl ++will call its dynamic loader routine (if there is one) and load the shared ++library. ++ ++The two arrays C<@ISA> and C<@EXPORT> are very important. The C<@ISA> ++array contains a list of other packages in which to search for methods (or ++subroutines) that do not exist in the current package. This is usually ++only important for object-oriented extensions (which we will talk about ++much later), and so usually doesn't need to be modified. ++ ++The C<@EXPORT> array tells Perl which of the extension's variables and ++subroutines should be placed into the calling package's namespace. Because ++you don't know if the user has already used your variable and subroutine ++names, it's vitally important to carefully select what to export. Do I ++export method or variable names I without a good reason. ++ ++As a general rule, if the module is trying to be object-oriented then don't ++export anything. If it's just a collection of functions and variables, then ++you can export them via another array, called C<@EXPORT_OK>. This array ++does not automatically place its subroutine and variable names into the ++namespace unless the user specifically requests that this be done. ++ ++See L for more information. ++ ++The C<$VERSION> variable is used to ensure that the .pm file and the shared ++library are "in sync" with each other. Any time you make changes to ++the .pm or .xs files, you should increment the value of this variable. ++ ++=head2 Writing good test scripts ++ ++The importance of writing good test scripts cannot be over-emphasized. You ++should closely follow the "ok/not ok" style that Perl itself uses, so that ++it is very easy and unambiguous to determine the outcome of each test case. ++When you find and fix a bug, make sure you add a test case for it. ++ ++By running "C", you ensure that your Mytest.t script runs and uses ++the correct version of your extension. If you have many test cases, ++save your test files in the "t" directory and use the suffix ".t". ++When you run "C", all of these test files will be executed. ++ ++=head2 EXAMPLE 3 ++ ++Our third extension will take one argument as its input, round off that ++value, and set the I to the rounded value. ++ ++Add the following to the end of Mytest.xs: ++ ++ void ++ round(arg) ++ double arg ++ CODE: ++ if (arg > 0.0) { ++ arg = floor(arg + 0.5); ++ } else if (arg < 0.0) { ++ arg = ceil(arg - 0.5); ++ } else { ++ arg = 0.0; ++ } ++ OUTPUT: ++ arg ++ ++Edit the Makefile.PL file so that the corresponding line looks like this: ++ ++ 'LIBS' => ['-lm'], # e.g., '-lm' ++ ++Generate the Makefile and run make. Change the test number in Mytest.t to ++"9" and add the following tests: ++ ++ $i = -1.5; &Mytest::round($i); is( $i, -2.0 ); ++ $i = -1.1; &Mytest::round($i); is( $i, -1.0 ); ++ $i = 0.0; &Mytest::round($i); is( $i, 0.0 ); ++ $i = 0.5; &Mytest::round($i); is( $i, 1.0 ); ++ $i = 1.2; &Mytest::round($i); is( $i, 1.0 ); ++ ++Running "C" should now print out that all nine tests are okay. ++ ++Notice that in these new test cases, the argument passed to round was a ++scalar variable. You might be wondering if you can round a constant or ++literal. To see what happens, temporarily add the following line to Mytest.t: ++ ++ &Mytest::round(3); ++ ++Run "C" and notice that Perl dies with a fatal error. Perl won't ++let you change the value of constants! ++ ++=head2 What's new here? ++ ++=over 4 ++ ++=item * ++ ++We've made some changes to Makefile.PL. In this case, we've specified an ++extra library to be linked into the extension's shared library, the math ++library libm in this case. We'll talk later about how to write XSUBs that ++can call every routine in a library. ++ ++=item * ++ ++The value of the function is not being passed back as the function's return ++value, but by changing the value of the variable that was passed into the ++function. You might have guessed that when you saw that the return value ++of round is of type "void". ++ ++=back ++ ++=head2 Input and Output Parameters ++ ++You specify the parameters that will be passed into the XSUB on the line(s) ++after you declare the function's return value and name. Each input parameter ++line starts with optional whitespace, and may have an optional terminating ++semicolon. ++ ++The list of output parameters occurs at the very end of the function, just ++after the OUTPUT: directive. The use of RETVAL tells Perl that you ++wish to send this value back as the return value of the XSUB function. In ++Example 3, we wanted the "return value" placed in the original variable ++which we passed in, so we listed it (and not RETVAL) in the OUTPUT: section. ++ ++=head2 The XSUBPP Program ++ ++The B program takes the XS code in the .xs file and translates it into ++C code, placing it in a file whose suffix is .c. The C code created makes ++heavy use of the C functions within Perl. ++ ++=head2 The TYPEMAP file ++ ++The B program uses rules to convert from Perl's data types (scalar, ++array, etc.) to C's data types (int, char, etc.). These rules are stored ++in the typemap file ($PERLLIB/ExtUtils/typemap). There's a brief discussion ++below, but all the nitty-gritty details can be found in L. ++If you have a new-enough version of perl (5.16 and up) or an upgraded ++XS compiler (C 3.13_01 or better), then you can inline ++typemaps in your XS instead of writing separate files. ++Either way, this typemap thing is split into three parts: ++ ++The first section maps various C data types to a name, which corresponds ++somewhat with the various Perl types. The second section contains C code ++which B uses to handle input parameters. The third section contains ++C code which B uses to handle output parameters. ++ ++Let's take a look at a portion of the .c file created for our extension. ++The file name is Mytest.c: ++ ++ XS(XS_Mytest_round) ++ { ++ dXSARGS; ++ if (items != 1) ++ Perl_croak(aTHX_ "Usage: Mytest::round(arg)"); ++ PERL_UNUSED_VAR(cv); /* -W */ ++ { ++ double arg = (double)SvNV(ST(0)); /* XXXXX */ ++ if (arg > 0.0) { ++ arg = floor(arg + 0.5); ++ } else if (arg < 0.0) { ++ arg = ceil(arg - 0.5); ++ } else { ++ arg = 0.0; ++ } ++ sv_setnv(ST(0), (double)arg); /* XXXXX */ ++ SvSETMAGIC(ST(0)); ++ } ++ XSRETURN_EMPTY; ++ } ++ ++Notice the two lines commented with "XXXXX". If you check the first part ++of the typemap file (or section), you'll see that doubles are of type ++T_DOUBLE. In the INPUT part of the typemap, an argument that is T_DOUBLE ++is assigned to the variable arg by calling the routine SvNV on something, ++then casting it to double, then assigned to the variable arg. Similarly, ++in the OUTPUT section, once arg has its final value, it is passed to the ++sv_setnv function to be passed back to the calling subroutine. These two ++functions are explained in L; we'll talk more later about what ++that "ST(0)" means in the section on the argument stack. ++ ++=head2 Warning about Output Arguments ++ ++In general, it's not a good idea to write extensions that modify their input ++parameters, as in Example 3. Instead, you should probably return multiple ++values in an array and let the caller handle them (we'll do this in a later ++example). However, in order to better accommodate calling pre-existing C ++routines, which often do modify their input parameters, this behavior is ++tolerated. ++ ++=head2 EXAMPLE 4 ++ ++In this example, we'll now begin to write XSUBs that will interact with ++pre-defined C libraries. To begin with, we will build a small library of ++our own, then let h2xs write our .pm and .xs files for us. ++ ++Create a new directory called Mytest2 at the same level as the directory ++Mytest. In the Mytest2 directory, create another directory called mylib, ++and cd into that directory. ++ ++Here we'll create some files that will generate a test library. These will ++include a C source file and a header file. We'll also create a Makefile.PL ++in this directory. Then we'll make sure that running make at the Mytest2 ++level will automatically run this Makefile.PL file and the resulting Makefile. ++ ++In the mylib directory, create a file mylib.h that looks like this: ++ ++ #define TESTVAL 4 ++ ++ extern double foo(int, long, const char*); ++ ++Also create a file mylib.c that looks like this: ++ ++ #include ++ #include "./mylib.h" ++ ++ double ++ foo(int a, long b, const char *c) ++ { ++ return (a + b + atof(c) + TESTVAL); ++ } ++ ++And finally create a file Makefile.PL that looks like this: ++ ++ use ExtUtils::MakeMaker; ++ $Verbose = 1; ++ WriteMakefile( ++ NAME => 'Mytest2::mylib', ++ SKIP => [qw(all static static_lib dynamic dynamic_lib)], ++ clean => {'FILES' => 'libmylib$(LIB_EXT)'}, ++ ); ++ ++ ++ sub MY::top_targets { ++ ' ++ all :: static ++ ++ pure_all :: static ++ ++ static :: libmylib$(LIB_EXT) ++ ++ libmylib$(LIB_EXT): $(O_FILES) ++ $(AR) cr libmylib$(LIB_EXT) $(O_FILES) ++ $(RANLIB) libmylib$(LIB_EXT) ++ ++ '; ++ } ++ ++Make sure you use a tab and not spaces on the lines beginning with "$(AR)" ++and "$(RANLIB)". Make will not function properly if you use spaces. ++It has also been reported that the "cr" argument to $(AR) is unnecessary ++on Win32 systems. ++ ++We will now create the main top-level Mytest2 files. Change to the directory ++above Mytest2 and run the following command: ++ ++ % h2xs -O -n Mytest2 ./Mytest2/mylib/mylib.h ++ ++This will print out a warning about overwriting Mytest2, but that's okay. ++Our files are stored in Mytest2/mylib, and will be untouched. ++ ++The normal Makefile.PL that h2xs generates doesn't know about the mylib ++directory. We need to tell it that there is a subdirectory and that we ++will be generating a library in it. Let's add the argument MYEXTLIB to ++the WriteMakefile call so that it looks like this: ++ ++ WriteMakefile( ++ 'NAME' => 'Mytest2', ++ 'VERSION_FROM' => 'Mytest2.pm', # finds $VERSION ++ 'LIBS' => [''], # e.g., '-lm' ++ 'DEFINE' => '', # e.g., '-DHAVE_SOMETHING' ++ 'INC' => '', # e.g., '-I/usr/include/other' ++ 'MYEXTLIB' => 'mylib/libmylib$(LIB_EXT)', ++ ); ++ ++and then at the end add a subroutine (which will override the pre-existing ++subroutine). Remember to use a tab character to indent the line beginning ++with "cd"! ++ ++ sub MY::postamble { ++ ' ++ $(MYEXTLIB): mylib/Makefile ++ cd mylib && $(MAKE) $(PASSTHRU) ++ '; ++ } ++ ++Let's also fix the MANIFEST file so that it accurately reflects the contents ++of our extension. The single line that says "mylib" should be replaced by ++the following three lines: ++ ++ mylib/Makefile.PL ++ mylib/mylib.c ++ mylib/mylib.h ++ ++To keep our namespace nice and unpolluted, edit the .pm file and change ++the variable C<@EXPORT> to C<@EXPORT_OK>. Finally, in the ++.xs file, edit the #include line to read: ++ ++ #include "mylib/mylib.h" ++ ++And also add the following function definition to the end of the .xs file: ++ ++ double ++ foo(a,b,c) ++ int a ++ long b ++ const char * c ++ OUTPUT: ++ RETVAL ++ ++Now we also need to create a typemap because the default Perl doesn't ++currently support the C type. Include a new TYPEMAP ++section in your XS code before the above function: ++ ++ TYPEMAP: <" and all should be well. There are some warnings on missing ++tests for the Mytest2::mylib extension, but you can ignore them. ++ ++=head2 What has happened here? ++ ++Unlike previous examples, we've now run h2xs on a real include file. This ++has caused some extra goodies to appear in both the .pm and .xs files. ++ ++=over 4 ++ ++=item * ++ ++In the .xs file, there's now a #include directive with the absolute path to ++the mylib.h header file. We changed this to a relative path so that we ++could move the extension directory if we wanted to. ++ ++=item * ++ ++There's now some new C code that's been added to the .xs file. The purpose ++of the C routine is to make the values that are #define'd in the ++header file accessible by the Perl script (by calling either C or ++C<&Mytest2::TESTVAL>). There's also some XS code to allow calls to the ++C routine. ++ ++=item * ++ ++The .pm file originally exported the name C in the C<@EXPORT> array. ++This could lead to name clashes. A good rule of thumb is that if the #define ++is only going to be used by the C routines themselves, and not by the user, ++they should be removed from the C<@EXPORT> array. Alternately, if you don't ++mind using the "fully qualified name" of a variable, you could move most ++or all of the items from the C<@EXPORT> array into the C<@EXPORT_OK> array. ++ ++=item * ++ ++If our include file had contained #include directives, these would not have ++been processed by h2xs. There is no good solution to this right now. ++ ++=item * ++ ++We've also told Perl about the library that we built in the mylib ++subdirectory. That required only the addition of the C variable ++to the WriteMakefile call and the replacement of the postamble subroutine ++to cd into the subdirectory and run make. The Makefile.PL for the ++library is a bit more complicated, but not excessively so. Again we ++replaced the postamble subroutine to insert our own code. This code ++simply specified that the library to be created here was a static archive ++library (as opposed to a dynamically loadable library) and provided the ++commands to build it. ++ ++=back ++ ++=head2 Anatomy of .xs file ++ ++The .xs file of L<"EXAMPLE 4"> contained some new elements. To understand ++the meaning of these elements, pay attention to the line which reads ++ ++ MODULE = Mytest2 PACKAGE = Mytest2 ++ ++Anything before this line is plain C code which describes which headers ++to include, and defines some convenience functions. No translations are ++performed on this part, apart from having embedded POD documentation ++skipped over (see L) it goes into the generated output C file as is. ++ ++Anything after this line is the description of XSUB functions. ++These descriptions are translated by B into C code which ++implements these functions using Perl calling conventions, and which ++makes these functions visible from Perl interpreter. ++ ++Pay a special attention to the function C. This name appears ++twice in the generated .xs file: once in the first part, as a static C ++function, then another time in the second part, when an XSUB interface to ++this static C function is defined. ++ ++This is quite typical for .xs files: usually the .xs file provides ++an interface to an existing C function. Then this C function is defined ++somewhere (either in an external library, or in the first part of .xs file), ++and a Perl interface to this function (i.e. "Perl glue") is described in the ++second part of .xs file. The situation in L<"EXAMPLE 1">, L<"EXAMPLE 2">, ++and L<"EXAMPLE 3">, when all the work is done inside the "Perl glue", is ++somewhat of an exception rather than the rule. ++ ++=head2 Getting the fat out of XSUBs ++ ++In L<"EXAMPLE 4"> the second part of .xs file contained the following ++description of an XSUB: ++ ++ double ++ foo(a,b,c) ++ int a ++ long b ++ const char * c ++ OUTPUT: ++ RETVAL ++ ++Note that in contrast with L<"EXAMPLE 1">, L<"EXAMPLE 2"> and L<"EXAMPLE 3">, ++this description does not contain the actual I for what is done ++during a call to Perl function foo(). To understand what is going ++on here, one can add a CODE section to this XSUB: ++ ++ double ++ foo(a,b,c) ++ int a ++ long b ++ const char * c ++ CODE: ++ RETVAL = foo(a,b,c); ++ OUTPUT: ++ RETVAL ++ ++However, these two XSUBs provide almost identical generated C code: B ++compiler is smart enough to figure out the C section from the first ++two lines of the description of XSUB. What about C section? In ++fact, that is absolutely the same! The C section can be removed ++as well, I section or C section> is not ++specified: B can see that it needs to generate a function call ++section, and will autogenerate the OUTPUT section too. Thus one can ++shortcut the XSUB to become: ++ ++ double ++ foo(a,b,c) ++ int a ++ long b ++ const char * c ++ ++Can we do the same with an XSUB ++ ++ int ++ is_even(input) ++ int input ++ CODE: ++ RETVAL = (input % 2 == 0); ++ OUTPUT: ++ RETVAL ++ ++of L<"EXAMPLE 2">? To do this, one needs to define a C function C. As we saw in L, a proper place ++for this definition is in the first part of .xs file. In fact a C function ++ ++ int ++ is_even(int arg) ++ { ++ return (arg % 2 == 0); ++ } ++ ++is probably overkill for this. Something as simple as a C<#define> will ++do too: ++ ++ #define is_even(arg) ((arg) % 2 == 0) ++ ++After having this in the first part of .xs file, the "Perl glue" part becomes ++as simple as ++ ++ int ++ is_even(input) ++ int input ++ ++This technique of separation of the glue part from the workhorse part has ++obvious tradeoffs: if you want to change a Perl interface, you need to ++change two places in your code. However, it removes a lot of clutter, ++and makes the workhorse part independent from idiosyncrasies of Perl calling ++convention. (In fact, there is nothing Perl-specific in the above description, ++a different version of B might have translated this to TCL glue or ++Python glue as well.) ++ ++=head2 More about XSUB arguments ++ ++With the completion of Example 4, we now have an easy way to simulate some ++real-life libraries whose interfaces may not be the cleanest in the world. ++We shall now continue with a discussion of the arguments passed to the ++B compiler. ++ ++When you specify arguments to routines in the .xs file, you are really ++passing three pieces of information for each argument listed. The first ++piece is the order of that argument relative to the others (first, second, ++etc). The second is the type of argument, and consists of the type ++declaration of the argument (e.g., int, char*, etc). The third piece is ++the calling convention for the argument in the call to the library function. ++ ++While Perl passes arguments to functions by reference, ++C passes arguments by value; to implement a C function which modifies data ++of one of the "arguments", the actual argument of this C function would be ++a pointer to the data. Thus two C functions with declarations ++ ++ int string_length(char *s); ++ int upper_case_char(char *cp); ++ ++may have completely different semantics: the first one may inspect an array ++of chars pointed by s, and the second one may immediately dereference C ++and manipulate C<*cp> only (using the return value as, say, a success ++indicator). From Perl one would use these functions in ++a completely different manner. ++ ++One conveys this info to B by replacing C<*> before the ++argument by C<&>. C<&> means that the argument should be passed to a library ++function by its address. The above two function may be XSUB-ified as ++ ++ int ++ string_length(s) ++ char * s ++ ++ int ++ upper_case_char(cp) ++ char &cp ++ ++For example, consider: ++ ++ int ++ foo(a,b) ++ char &a ++ char * b ++ ++The first Perl argument to this function would be treated as a char and ++assigned to the variable a, and its address would be passed into the function ++foo. The second Perl argument would be treated as a string pointer and assigned ++to the variable b. The I of b would be passed into the function foo. ++The actual call to the function foo that B generates would look like ++this: ++ ++ foo(&a, b); ++ ++B will parse the following function argument lists identically: ++ ++ char &a ++ char&a ++ char & a ++ ++However, to help ease understanding, it is suggested that you place a "&" ++next to the variable name and away from the variable type), and place a ++"*" near the variable type, but away from the variable name (as in the ++call to foo above). By doing so, it is easy to understand exactly what ++will be passed to the C function; it will be whatever is in the "last ++column". ++ ++You should take great pains to try to pass the function the type of variable ++it wants, when possible. It will save you a lot of trouble in the long run. ++ ++=head2 The Argument Stack ++ ++If we look at any of the C code generated by any of the examples except ++example 1, you will notice a number of references to ST(n), where n is ++usually 0. "ST" is actually a macro that points to the n'th argument ++on the argument stack. ST(0) is thus the first argument on the stack and ++therefore the first argument passed to the XSUB, ST(1) is the second ++argument, and so on. ++ ++When you list the arguments to the XSUB in the .xs file, that tells B ++which argument corresponds to which of the argument stack (i.e., the first ++one listed is the first argument, and so on). You invite disaster if you ++do not list them in the same order as the function expects them. ++ ++The actual values on the argument stack are pointers to the values passed ++in. When an argument is listed as being an OUTPUT value, its corresponding ++value on the stack (i.e., ST(0) if it was the first argument) is changed. ++You can verify this by looking at the C code generated for Example 3. ++The code for the round() XSUB routine contains lines that look like this: ++ ++ double arg = (double)SvNV(ST(0)); ++ /* Round the contents of the variable arg */ ++ sv_setnv(ST(0), (double)arg); ++ ++The arg variable is initially set by taking the value from ST(0), then is ++stored back into ST(0) at the end of the routine. ++ ++XSUBs are also allowed to return lists, not just scalars. This must be ++done by manipulating stack values ST(0), ST(1), etc, in a subtly ++different way. See L for details. ++ ++XSUBs are also allowed to avoid automatic conversion of Perl function arguments ++to C function arguments. See L for details. Some people prefer ++manual conversion by inspecting C even in the cases when automatic ++conversion will do, arguing that this makes the logic of an XSUB call clearer. ++Compare with L<"Getting the fat out of XSUBs"> for a similar tradeoff of ++a complete separation of "Perl glue" and "workhorse" parts of an XSUB. ++ ++While experts may argue about these idioms, a novice to Perl guts may ++prefer a way which is as little Perl-guts-specific as possible, meaning ++automatic conversion and automatic call generation, as in ++L<"Getting the fat out of XSUBs">. This approach has the additional ++benefit of protecting the XSUB writer from future changes to the Perl API. ++ ++=head2 Extending your Extension ++ ++Sometimes you might want to provide some extra methods or subroutines ++to assist in making the interface between Perl and your extension simpler ++or easier to understand. These routines should live in the .pm file. ++Whether they are automatically loaded when the extension itself is loaded ++or only loaded when called depends on where in the .pm file the subroutine ++definition is placed. You can also consult L for an alternate ++way to store and load your extra subroutines. ++ ++=head2 Documenting your Extension ++ ++There is absolutely no excuse for not documenting your extension. ++Documentation belongs in the .pm file. This file will be fed to pod2man, ++and the embedded documentation will be converted to the manpage format, ++then placed in the blib directory. It will be copied to Perl's ++manpage directory when the extension is installed. ++ ++You may intersperse documentation and Perl code within the .pm file. ++In fact, if you want to use method autoloading, you must do this, ++as the comment inside the .pm file explains. ++ ++See L for more information about the pod format. ++ ++=head2 Installing your Extension ++ ++Once your extension is complete and passes all its tests, installing it ++is quite simple: you simply run "make install". You will either need ++to have write permission into the directories where Perl is installed, ++or ask your system administrator to run the make for you. ++ ++Alternately, you can specify the exact directory to place the extension's ++files by placing a "PREFIX=/destination/directory" after the make install ++(or in between the make and install if you have a brain-dead version of make). ++This can be very useful if you are building an extension that will eventually ++be distributed to multiple systems. You can then just archive the files in ++the destination directory and distribute them to your destination systems. ++ ++=head2 EXAMPLE 5 ++ ++In this example, we'll do some more work with the argument stack. The ++previous examples have all returned only a single value. We'll now ++create an extension that returns an array. ++ ++This extension is very Unix-oriented (struct statfs and the statfs system ++call). If you are not running on a Unix system, you can substitute for ++statfs any other function that returns multiple values, you can hard-code ++values to be returned to the caller (although this will be a bit harder ++to test the error case), or you can simply not do this example. If you ++change the XSUB, be sure to fix the test cases to match the changes. ++ ++Return to the Mytest directory and add the following code to the end of ++Mytest.xs: ++ ++ void ++ statfs(path) ++ char * path ++ INIT: ++ int i; ++ struct statfs buf; ++ ++ PPCODE: ++ i = statfs(path, &buf); ++ if (i == 0) { ++ XPUSHs(sv_2mortal(newSVnv(buf.f_bavail))); ++ XPUSHs(sv_2mortal(newSVnv(buf.f_bfree))); ++ XPUSHs(sv_2mortal(newSVnv(buf.f_blocks))); ++ XPUSHs(sv_2mortal(newSVnv(buf.f_bsize))); ++ XPUSHs(sv_2mortal(newSVnv(buf.f_ffree))); ++ XPUSHs(sv_2mortal(newSVnv(buf.f_files))); ++ XPUSHs(sv_2mortal(newSVnv(buf.f_type))); ++ } else { ++ XPUSHs(sv_2mortal(newSVnv(errno))); ++ } ++ ++You'll also need to add the following code to the top of the .xs file, just ++after the include of "XSUB.h": ++ ++ #include ++ ++Also add the following code segment to Mytest.t while incrementing the "9" ++tests to "11": ++ ++ @a = &Mytest::statfs("/blech"); ++ ok( scalar(@a) == 1 && $a[0] == 2 ); ++ @a = &Mytest::statfs("/"); ++ is( scalar(@a), 7 ); ++ ++=head2 New Things in this Example ++ ++This example added quite a few new concepts. We'll take them one at a time. ++ ++=over 4 ++ ++=item * ++ ++The INIT: directive contains code that will be placed immediately after ++the argument stack is decoded. C does not allow variable declarations at ++arbitrary locations inside a function, ++so this is usually the best way to declare local variables needed by the XSUB. ++(Alternatively, one could put the whole C section into braces, and ++put these declarations on top.) ++ ++=item * ++ ++This routine also returns a different number of arguments depending on the ++success or failure of the call to statfs. If there is an error, the error ++number is returned as a single-element array. If the call is successful, ++then a 7-element array is returned. Since only one argument is passed into ++this function, we need room on the stack to hold the 7 values which may be ++returned. ++ ++We do this by using the PPCODE: directive, rather than the CODE: directive. ++This tells B that we will be managing the return values that will be ++put on the argument stack by ourselves. ++ ++=item * ++ ++When we want to place values to be returned to the caller onto the stack, ++we use the series of macros that begin with "XPUSH". There are five ++different versions, for placing integers, unsigned integers, doubles, ++strings, and Perl scalars on the stack. In our example, we placed a ++Perl scalar onto the stack. (In fact this is the only macro which ++can be used to return multiple values.) ++ ++The XPUSH* macros will automatically extend the return stack to prevent ++it from being overrun. You push values onto the stack in the order you ++want them seen by the calling program. ++ ++=item * ++ ++The values pushed onto the return stack of the XSUB are actually mortal SV's. ++They are made mortal so that once the values are copied by the calling ++program, the SV's that held the returned values can be deallocated. ++If they were not mortal, then they would continue to exist after the XSUB ++routine returned, but would not be accessible. This is a memory leak. ++ ++=item * ++ ++If we were interested in performance, not in code compactness, in the success ++branch we would not use C macros, but C macros, and would ++pre-extend the stack before pushing the return values: ++ ++ EXTEND(SP, 7); ++ ++The tradeoff is that one needs to calculate the number of return values ++in advance (though overextending the stack will not typically hurt ++anything but memory consumption). ++ ++Similarly, in the failure branch we could use C I extending ++the stack: the Perl function reference comes to an XSUB on the stack, thus ++the stack is I large enough to take one return value. ++ ++=back ++ ++=head2 EXAMPLE 6 ++ ++In this example, we will accept a reference to an array as an input ++parameter, and return a reference to an array of hashes. This will ++demonstrate manipulation of complex Perl data types from an XSUB. ++ ++This extension is somewhat contrived. It is based on the code in ++the previous example. It calls the statfs function multiple times, ++accepting a reference to an array of filenames as input, and returning ++a reference to an array of hashes containing the data for each of the ++filesystems. ++ ++Return to the Mytest directory and add the following code to the end of ++Mytest.xs: ++ ++ SV * ++ multi_statfs(paths) ++ SV * paths ++ INIT: ++ AV * results; ++ SSize_t numpaths = 0, n; ++ int i; ++ struct statfs buf; ++ ++ SvGETMAGIC(paths); ++ if ((!SvROK(paths)) ++ || (SvTYPE(SvRV(paths)) != SVt_PVAV) ++ || ((numpaths = av_top_index((AV *)SvRV(paths))) < 0)) ++ { ++ XSRETURN_UNDEF; ++ } ++ results = (AV *)sv_2mortal((SV *)newAV()); ++ CODE: ++ for (n = 0; n <= numpaths; n++) { ++ HV * rh; ++ STRLEN l; ++ char * fn = SvPV(*av_fetch((AV *)SvRV(paths), n, 0), l); ++ ++ i = statfs(fn, &buf); ++ if (i != 0) { ++ av_push(results, newSVnv(errno)); ++ continue; ++ } ++ ++ rh = (HV *)sv_2mortal((SV *)newHV()); ++ ++ hv_store(rh, "f_bavail", 8, newSVnv(buf.f_bavail), 0); ++ hv_store(rh, "f_bfree", 7, newSVnv(buf.f_bfree), 0); ++ hv_store(rh, "f_blocks", 8, newSVnv(buf.f_blocks), 0); ++ hv_store(rh, "f_bsize", 7, newSVnv(buf.f_bsize), 0); ++ hv_store(rh, "f_ffree", 7, newSVnv(buf.f_ffree), 0); ++ hv_store(rh, "f_files", 7, newSVnv(buf.f_files), 0); ++ hv_store(rh, "f_type", 6, newSVnv(buf.f_type), 0); ++ ++ av_push(results, newRV_inc((SV *)rh)); ++ } ++ RETVAL = newRV_inc((SV *)results); ++ OUTPUT: ++ RETVAL ++ ++And add the following code to Mytest.t, while incrementing the "11" ++tests to "13": ++ ++ $results = Mytest::multi_statfs([ '/', '/blech' ]); ++ ok( ref $results->[0] ); ++ ok( ! ref $results->[1] ); ++ ++=head2 New Things in this Example ++ ++There are a number of new concepts introduced here, described below: ++ ++=over 4 ++ ++=item * ++ ++This function does not use a typemap. Instead, we declare it as accepting ++one SV* (scalar) parameter, and returning an SV* value, and we take care of ++populating these scalars within the code. Because we are only returning ++one value, we don't need a C directive - instead, we use C ++and C directives. ++ ++=item * ++ ++When dealing with references, it is important to handle them with caution. ++The C block first calls SvGETMAGIC(paths), in case ++paths is a tied variable. Then it checks that C returns ++true, which indicates that paths is a valid reference. (Simply ++checking C won't trigger FETCH on a tied variable.) It ++then verifies that the object referenced by paths is an array, using C ++to dereference paths, and C to discover its type. As an added test, ++it checks that the array referenced by paths is non-empty, using the ++C function (which returns -1 if the array is empty). The ++XSRETURN_UNDEF macro is used to abort the XSUB and return the undefined value ++whenever all three of these conditions are not met. ++ ++=item * ++ ++We manipulate several arrays in this XSUB. Note that an array is represented ++internally by an AV* pointer. The functions and macros for manipulating ++arrays are similar to the functions in Perl: C returns the ++highest index in an AV*, much like $#array; C fetches a single scalar ++value from an array, given its index; C pushes a scalar value onto the ++end of the array, automatically extending the array as necessary. ++ ++Specifically, we read pathnames one at a time from the input array, and ++store the results in an output array (results) in the same order. If ++statfs fails, the element pushed onto the return array is the value of ++errno after the failure. If statfs succeeds, though, the value pushed ++onto the return array is a reference to a hash containing some of the ++information in the statfs structure. ++ ++As with the return stack, it would be possible (and a small performance win) ++to pre-extend the return array before pushing data into it, since we know ++how many elements we will return: ++ ++ av_extend(results, numpaths); ++ ++=item * ++ ++We are performing only one hash operation in this function, which is storing ++a new scalar under a key using C. A hash is represented by an HV* ++pointer. Like arrays, the functions for manipulating hashes from an XSUB ++mirror the functionality available from Perl. See L and L ++for details. ++ ++=item * ++ ++To create a reference, we use the C function. Note that you can ++cast an AV* or an HV* to type SV* in this case (and many others). This ++allows you to take references to arrays, hashes and scalars with the same ++function. Conversely, the C function always returns an SV*, which may ++need to be cast to the appropriate type if it is something other than a ++scalar (check with C). ++ ++=item * ++ ++At this point, xsubpp is doing very little work - the differences between ++Mytest.xs and Mytest.c are minimal. ++ ++=back ++ ++=head2 EXAMPLE 7 (Coming Soon) ++ ++XPUSH args AND set RETVAL AND assign return value to array ++ ++=head2 EXAMPLE 8 (Coming Soon) ++ ++Setting $! ++ ++=head2 EXAMPLE 9 Passing open files to XSes ++ ++You would think passing files to an XS is difficult, with all the ++typeglobs and stuff. Well, it isn't. ++ ++Suppose that for some strange reason we need a wrapper around the ++standard C library function C. This is all we need: ++ ++ #define PERLIO_NOT_STDIO 0 ++ #define PERL_NO_GET_CONTEXT ++ #include "EXTERN.h" ++ #include "perl.h" ++ #include "XSUB.h" ++ ++ #include ++ ++ int ++ fputs(s, stream) ++ char * s ++ FILE * stream ++ ++The real work is done in the standard typemap. ++ ++B you lose all the fine stuff done by the perlio layers. This ++calls the stdio function C, which knows nothing about them. ++ ++The standard typemap offers three variants of PerlIO *: ++C (T_IN), C (T_INOUT) and C ++(T_OUT). A bare C is considered a T_INOUT. If it matters ++in your code (see below for why it might) #define or typedef ++one of the specific names and use that as the argument or result ++type in your XS file. ++ ++The standard typemap does not contain PerlIO * before perl 5.7, ++but it has the three stream variants. Using a PerlIO * directly ++is not backwards compatible unless you provide your own typemap. ++ ++For streams coming I perl the main difference is that ++C will get the output PerlIO * - which may make ++a difference on a socket. Like in our example... ++ ++For streams being handed I perl a new file handle is created ++(i.e. a reference to a new glob) and associated with the PerlIO * ++provided. If the read/write state of the PerlIO * is not correct then you ++may get errors or warnings from when the file handle is used. ++So if you opened the PerlIO * as "w" it should really be an ++C if open as "r" it should be an C. ++ ++Now, suppose you want to use perlio layers in your XS. We'll use the ++perlio C function as an example. ++ ++In the C part of the XS file (above the first MODULE line) you ++have ++ ++ #define OutputStream PerlIO * ++ or ++ typedef PerlIO * OutputStream; ++ ++ ++And this is the XS code: ++ ++ int ++ perlioputs(s, stream) ++ char * s ++ OutputStream stream ++ CODE: ++ RETVAL = PerlIO_puts(stream, s); ++ OUTPUT: ++ RETVAL ++ ++We have to use a C section because C has the arguments ++reversed compared to C, and we want to keep the arguments the same. ++ ++Wanting to explore this thoroughly, we want to use the stdio C ++on a PerlIO *. This means we have to ask the perlio system for a stdio ++C: ++ ++ int ++ perliofputs(s, stream) ++ char * s ++ OutputStream stream ++ PREINIT: ++ FILE *fp = PerlIO_findFILE(stream); ++ CODE: ++ if (fp != (FILE*) 0) { ++ RETVAL = fputs(s, fp); ++ } else { ++ RETVAL = -1; ++ } ++ OUTPUT: ++ RETVAL ++ ++Note: C will search the layers for a stdio ++layer. If it can't find one, it will call C to ++generate a new stdio C. Please only call C if ++you want a I C. It will generate one on each call and push a ++new stdio layer. So don't call it repeatedly on the same ++file. C will retrieve the stdio layer once it has been ++generated by C. ++ ++This applies to the perlio system only. For versions before 5.7, ++C is equivalent to C. ++ ++=head2 Troubleshooting these Examples ++ ++As mentioned at the top of this document, if you are having problems with ++these example extensions, you might see if any of these help you. ++ ++=over 4 ++ ++=item * ++ ++In versions of 5.002 prior to the gamma version, the test script in Example ++1 will not function properly. You need to change the "use lib" line to ++read: ++ ++ use lib './blib'; ++ ++=item * ++ ++In versions of 5.002 prior to version 5.002b1h, the test.pl file was not ++automatically created by h2xs. This means that you cannot say "make test" ++to run the test script. You will need to add the following line before the ++"use extension" statement: ++ ++ use lib './blib'; ++ ++=item * ++ ++In versions 5.000 and 5.001, instead of using the above line, you will need ++to use the following line: ++ ++ BEGIN { unshift(@INC, "./blib") } ++ ++=item * ++ ++This document assumes that the executable named "perl" is Perl version 5. ++Some systems may have installed Perl version 5 as "perl5". ++ ++=back ++ ++=head1 See also ++ ++For more information, consult L, L, L, L, ++and L. ++ ++=head1 Author ++ ++Jeff Okamoto > ++ ++Reviewed and assisted by Dean Roehrich, Ilya Zakharevich, Andreas Koenig, ++and Tim Bunce. ++ ++PerlIO material contributed by Lupe Christoph, with some clarification ++by Nick Ing-Simmons. ++ ++Changes for h2xs as of Perl 5.8.x by Renee Baecker ++ ++=head2 Last Changed ++ ++2012-01-20 +diff --git a/lib/perlxstypemap.pod b/lib/perlxstypemap.pod +new file mode 100644 +index 0000000..7d1f73c +--- /dev/null ++++ b/lib/perlxstypemap.pod +@@ -0,0 +1,711 @@ ++=head1 NAME ++ ++perlxstypemap - Perl XS C/Perl type mapping ++ ++=head1 DESCRIPTION ++ ++The more you think about interfacing between two languages, the more ++you'll realize that the majority of programmer effort has to go into ++converting between the data structures that are native to either of ++the languages involved. This trumps other matter such as differing ++calling conventions because the problem space is so much greater. ++There are simply more ways to shove data into memory than there are ++ways to implement a function call. ++ ++Perl XS' attempt at a solution to this is the concept of typemaps. ++At an abstract level, a Perl XS typemap is nothing but a recipe for ++converting from a certain Perl data structure to a certain C ++data structure and vice versa. Since there can be C types that ++are sufficiently similar to one another to warrant converting with ++the same logic, XS typemaps are represented by a unique identifier, ++henceforth called an B in this document. You can then tell ++the XS compiler that multiple C types are to be mapped with the same ++XS typemap. ++ ++In your XS code, when you define an argument with a C type or when ++you are using a C and an C section together with a ++C return type of your XSUB, it'll be the typemapping mechanism that ++makes this easy. ++ ++=head2 Anatomy of a typemap ++ ++In more practical terms, the typemap is a collection of code ++fragments which are used by the B compiler to map C function ++parameters and values to Perl values. The typemap file may consist ++of three sections labelled C, C, and C. ++An unlabelled initial section is assumed to be a C section. ++The INPUT section tells the compiler how to translate Perl values ++into variables of certain C types. The OUTPUT section tells the ++compiler how to translate the values from certain C types into values ++Perl can understand. The TYPEMAP section tells the compiler which ++of the INPUT and OUTPUT code fragments should be used to map a given ++C type to a Perl value. The section labels C, C, or ++C must begin in the first column on a line by themselves, ++and must be in uppercase. ++ ++Each type of section can appear an arbitrary number of times ++and does not have to appear at all. For example, a typemap may ++commonly lack C and C sections if all it needs to ++do is associate additional C types with core XS types like T_PTROBJ. ++Lines that start with a hash C<#> are considered comments and ignored ++in the C section, but are considered significant in C ++and C. Blank lines are generally ignored. ++ ++Traditionally, typemaps needed to be written to a separate file, ++conventionally called C in a CPAN distribution. With ++ExtUtils::ParseXS (the XS compiler) version 3.12 or better which ++comes with perl 5.16, typemaps can also be embedded directly into ++XS code using a HERE-doc like syntax: ++ ++ TYPEMAP: < can be replaced by other identifiers like with normal ++Perl HERE-docs. All details below about the typemap textual format ++remain valid. ++ ++The C section should contain one pair of C type and ++XS type per line as follows. An example from the core typemap file: ++ ++ TYPEMAP ++ # all variants of char* is handled by the T_PV typemap ++ char * T_PV ++ const char * T_PV ++ unsigned char * T_PV ++ ... ++ ++The C and C sections have identical formats, that is, ++each unindented line starts a new in- or output map respectively. ++A new in- or output map must start with the name of the XS type to ++map on a line by itself, followed by the code that implements it ++indented on the following lines. Example: ++ ++ INPUT ++ T_PV ++ $var = ($type)SvPV_nolen($arg) ++ T_PTR ++ $var = INT2PTR($type,SvIV($arg)) ++ ++We'll get to the meaning of those Perlish-looking variables in a ++little bit. ++ ++Finally, here's an example of the full typemap file for mapping C ++strings of the C type to Perl scalars/strings: ++ ++ TYPEMAP ++ char * T_PV ++ ++ INPUT ++ T_PV ++ $var = ($type)SvPV_nolen($arg) ++ ++ OUTPUT ++ T_PV ++ sv_setpv((SV*)$arg, $var); ++ ++Here's a more complicated example: suppose that you wanted ++C to be blessed into the class C. ++One way to do this is to use underscores (_) to separate package ++names, as follows: ++ ++ typedef struct netconfig * Net_Config; ++ ++And then provide a typemap entry C that maps ++underscores to double-colons (::), and declare C to be of ++that type: ++ ++ TYPEMAP ++ Net_Config T_PTROBJ_SPECIAL ++ ++ INPUT ++ T_PTROBJ_SPECIAL ++ if (sv_derived_from($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")){ ++ IV tmp = SvIV((SV*)SvRV($arg)); ++ $var = INT2PTR($type, tmp); ++ } ++ else ++ croak(\"$var is not of type ${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\") ++ ++ OUTPUT ++ T_PTROBJ_SPECIAL ++ sv_setref_pv($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\", ++ (void*)$var); ++ ++The INPUT and OUTPUT sections substitute underscores for double-colons ++on the fly, giving the desired effect. This example demonstrates some ++of the power and versatility of the typemap facility. ++ ++The C macro (defined in perl.h) casts an integer to a pointer ++of a given type, taking care of the possible different size of integers ++and pointers. There are also C, C, C macros, ++to map the other way, which may be useful in OUTPUT sections. ++ ++=head2 The Role of the typemap File in Your Distribution ++ ++The default typemap in the F directory of the Perl source ++contains many useful types which can be used by Perl extensions. Some ++extensions define additional typemaps which they keep in their own directory. ++These additional typemaps may reference INPUT and OUTPUT maps in the main ++typemap. The B compiler will allow the extension's own typemap to ++override any mappings which are in the default typemap. Instead of using ++an additional F file, typemaps may be embedded verbatim in XS ++with a heredoc-like syntax. See the documentation on the C XS ++keyword. ++ ++For CPAN distributions, you can assume that the XS types defined by ++the perl core are already available. Additionally, the core typemap ++has default XS types for a large number of C types. For example, if ++you simply return a C from your XSUB, the core typemap will ++have this C type associated with the T_PV XS type. That means your ++C string will be copied into the PV (pointer value) slot of a new scalar ++that will be returned from your XSUB to Perl. ++ ++If you're developing a CPAN distribution using XS, you may add your own ++file called F to the distribution. That file may contain ++typemaps that either map types that are specific to your code or that ++override the core typemap file's mappings for common C types. ++ ++=head2 Sharing typemaps Between CPAN Distributions ++ ++Starting with ExtUtils::ParseXS version 3.13_01 (comes with perl 5.16 ++and better), it is rather easy to share typemap code between multiple ++CPAN distributions. The general idea is to share it as a module that ++offers a certain API and have the dependent modules declare that as a ++built-time requirement and import the typemap into the XS. An example ++of such a typemap-sharing module on CPAN is ++C. Two steps to getting that module's ++typemaps available in your code: ++ ++=over 4 ++ ++=item * ++ ++Declare C as a build-time dependency ++in C (use C), or in your C ++(use C). ++ ++=item * ++ ++Include the following line in the XS section of your XS file: ++(don't break the line) ++ ++ INCLUDE_COMMAND: $^X -MExtUtils::Typemaps::Cmd ++ -e "print embeddable_typemap(q{Basic})" ++ ++=back ++ ++=head2 Writing typemap Entries ++ ++Each INPUT or OUTPUT typemap entry is a double-quoted Perl string that ++will be evaluated in the presence of certain variables to get the ++final C code for mapping a certain C type. ++ ++This means that you can embed Perl code in your typemap (C) code using ++constructs such as ++C<${ perl code that evaluates to scalar reference here }>. A common ++use case is to generate error messages that refer to the true function ++name even when using the ALIAS XS feature: ++ ++ ${ $ALIAS ? \q[GvNAME(CvGV(cv))] : \qq[\"$pname\"] } ++ ++For many typemap examples, refer to the core typemap file that can be ++found in the perl source tree at F. ++ ++The Perl variables that are available for interpolation into typemaps ++are the following: ++ ++=over 4 ++ ++=item * ++ ++I<$var> - the name of the input or output variable, eg. RETVAL for ++return values. ++ ++=item * ++ ++I<$type> - the raw C type of the parameter, any C<:> replaced with ++C<_>. ++e.g. for a type of C, I<$type> is C ++ ++=item * ++ ++I<$ntype> - the supplied type with C<*> replaced with C. ++e.g. for a type of C, I<$ntype> is C ++ ++=item * ++ ++I<$arg> - the stack entry, that the parameter is input from or output ++to, e.g. C ++ ++=item * ++ ++I<$argoff> - the argument stack offset of the argument. ie. 0 for the ++first argument, etc. ++ ++=item * ++ ++I<$pname> - the full name of the XSUB, with including the C ++name, with any C stripped. This is the non-ALIAS name. ++ ++=item * ++ ++I<$Package> - the package specified by the most recent C ++keyword. ++ ++=item * ++ ++I<$ALIAS> - non-zero if the current XSUB has any aliases declared with ++C. ++ ++=back ++ ++=head2 Full Listing of Core Typemaps ++ ++Each C type is represented by an entry in the typemap file that ++is responsible for converting perl variables (SV, AV, HV, CV, etc.) ++to and from that type. The following sections list all XS types ++that come with perl by default. ++ ++=over 4 ++ ++=item T_SV ++ ++This simply passes the C representation of the Perl variable (an SV*) ++in and out of the XS layer. This can be used if the C code wants ++to deal directly with the Perl variable. ++ ++=item T_SVREF ++ ++Used to pass in and return a reference to an SV. ++ ++Note that this typemap does not decrement the reference count ++when returning the reference to an SV*. ++See also: T_SVREF_REFCOUNT_FIXED ++ ++=item T_SVREF_FIXED ++ ++Used to pass in and return a reference to an SV. ++This is a fixed ++variant of T_SVREF that decrements the refcount appropriately ++when returning a reference to an SV*. Introduced in perl 5.15.4. ++ ++=item T_AVREF ++ ++From the perl level this is a reference to a perl array. ++From the C level this is a pointer to an AV. ++ ++Note that this typemap does not decrement the reference count ++when returning an AV*. See also: T_AVREF_REFCOUNT_FIXED ++ ++=item T_AVREF_REFCOUNT_FIXED ++ ++From the perl level this is a reference to a perl array. ++From the C level this is a pointer to an AV. This is a fixed ++variant of T_AVREF that decrements the refcount appropriately ++when returning an AV*. Introduced in perl 5.15.4. ++ ++=item T_HVREF ++ ++From the perl level this is a reference to a perl hash. ++From the C level this is a pointer to an HV. ++ ++Note that this typemap does not decrement the reference count ++when returning an HV*. See also: T_HVREF_REFCOUNT_FIXED ++ ++=item T_HVREF_REFCOUNT_FIXED ++ ++From the perl level this is a reference to a perl hash. ++From the C level this is a pointer to an HV. This is a fixed ++variant of T_HVREF that decrements the refcount appropriately ++when returning an HV*. Introduced in perl 5.15.4. ++ ++=item T_CVREF ++ ++From the perl level this is a reference to a perl subroutine ++(e.g. $sub = sub { 1 };). From the C level this is a pointer ++to a CV. ++ ++Note that this typemap does not decrement the reference count ++when returning an HV*. See also: T_HVREF_REFCOUNT_FIXED ++ ++=item T_CVREF_REFCOUNT_FIXED ++ ++From the perl level this is a reference to a perl subroutine ++(e.g. $sub = sub { 1 };). From the C level this is a pointer ++to a CV. ++ ++This is a fixed ++variant of T_HVREF that decrements the refcount appropriately ++when returning an HV*. Introduced in perl 5.15.4. ++ ++=item T_SYSRET ++ ++The T_SYSRET typemap is used to process return values from system calls. ++It is only meaningful when passing values from C to perl (there is ++no concept of passing a system return value from Perl to C). ++ ++System calls return -1 on error (setting ERRNO with the reason) ++and (usually) 0 on success. If the return value is -1 this typemap ++returns C. If the return value is not -1, this typemap ++translates a 0 (perl false) to "0 but true" (which ++is perl true) or returns the value itself, to indicate that the ++command succeeded. ++ ++The L module makes extensive use of this type. ++ ++=item T_UV ++ ++An unsigned integer. ++ ++=item T_IV ++ ++A signed integer. This is cast to the required integer type when ++passed to C and converted to an IV when passed back to Perl. ++ ++=item T_INT ++ ++A signed integer. This typemap converts the Perl value to a native ++integer type (the C type on the current platform). When returning ++the value to perl it is processed in the same way as for T_IV. ++ ++Its behaviour is identical to using an C type in XS with T_IV. ++ ++=item T_ENUM ++ ++An enum value. Used to transfer an enum component ++from C. There is no reason to pass an enum value to C since ++it is stored as an IV inside perl. ++ ++=item T_BOOL ++ ++A boolean type. This can be used to pass true and false values to and ++from C. ++ ++=item T_U_INT ++ ++This is for unsigned integers. It is equivalent to using T_UV ++but explicitly casts the variable to type C. ++The default type for C is T_UV. ++ ++=item T_SHORT ++ ++Short integers. This is equivalent to T_IV but explicitly casts ++the return to type C. The default typemap for C ++is T_IV. ++ ++=item T_U_SHORT ++ ++Unsigned short integers. This is equivalent to T_UV but explicitly ++casts the return to type C. The default typemap for ++C is T_UV. ++ ++T_U_SHORT is used for type C in the standard typemap. ++ ++=item T_LONG ++ ++Long integers. This is equivalent to T_IV but explicitly casts ++the return to type C. The default typemap for C ++is T_IV. ++ ++=item T_U_LONG ++ ++Unsigned long integers. This is equivalent to T_UV but explicitly ++casts the return to type C. The default typemap for ++C is T_UV. ++ ++T_U_LONG is used for type C in the standard typemap. ++ ++=item T_CHAR ++ ++Single 8-bit characters. ++ ++=item T_U_CHAR ++ ++An unsigned byte. ++ ++=item T_FLOAT ++ ++A floating point number. This typemap guarantees to return a variable ++cast to a C. ++ ++=item T_NV ++ ++A Perl floating point number. Similar to T_IV and T_UV in that the ++return type is cast to the requested numeric type rather than ++to a specific type. ++ ++=item T_DOUBLE ++ ++A double precision floating point number. This typemap guarantees to ++return a variable cast to a C. ++ ++=item T_PV ++ ++A string (char *). ++ ++=item T_PTR ++ ++A memory address (pointer). Typically associated with a C ++type. ++ ++=item T_PTRREF ++ ++Similar to T_PTR except that the pointer is stored in a scalar and the ++reference to that scalar is returned to the caller. This can be used ++to hide the actual pointer value from the programmer since it is usually ++not required directly from within perl. ++ ++The typemap checks that a scalar reference is passed from perl to XS. ++ ++=item T_PTROBJ ++ ++Similar to T_PTRREF except that the reference is blessed into a class. ++This allows the pointer to be used as an object. Most commonly used to ++deal with C structs. The typemap checks that the perl object passed ++into the XS routine is of the correct class (or part of a subclass). ++ ++The pointer is blessed into a class that is derived from the name ++of type of the pointer but with all '*' in the name replaced with ++'Ptr'. ++ ++For C XSUBs only, a T_PTROBJ is optimized to a T_PTRREF. This means ++the class check is skipped. ++ ++=item T_REF_IV_REF ++ ++NOT YET ++ ++=item T_REF_IV_PTR ++ ++Similar to T_PTROBJ in that the pointer is blessed into a scalar object. ++The difference is that when the object is passed back into XS it must be ++of the correct type (inheritance is not supported) while T_PTROBJ supports ++inheritance. ++ ++The pointer is blessed into a class that is derived from the name ++of type of the pointer but with all '*' in the name replaced with ++'Ptr'. ++ ++For C XSUBs only, a T_REF_IV_PTR is optimized to a T_PTRREF. This ++means the class check is skipped. ++ ++=item T_PTRDESC ++ ++NOT YET ++ ++=item T_REFREF ++ ++Similar to T_PTRREF, except the pointer stored in the referenced scalar ++is dereferenced and copied to the output variable. This means that ++T_REFREF is to T_PTRREF as T_OPAQUE is to T_OPAQUEPTR. All clear? ++ ++Only the INPUT part of this is implemented (Perl to XSUB) and there ++are no known users in core or on CPAN. ++ ++=item T_REFOBJ ++ ++Like T_REFREF, except it does strict type checking (inheritance is not ++supported). ++ ++For C XSUBs only, a T_REFOBJ is optimized to a T_REFREF. This means ++the class check is skipped. ++ ++=item T_OPAQUEPTR ++ ++This can be used to store bytes in the string component of the ++SV. Here the representation of the data is irrelevant to perl and the ++bytes themselves are just stored in the SV. It is assumed that the C ++variable is a pointer (the bytes are copied from that memory ++location). If the pointer is pointing to something that is ++represented by 8 bytes then those 8 bytes are stored in the SV (and ++length() will report a value of 8). This entry is similar to T_OPAQUE. ++ ++In principle the unpack() command can be used to convert the bytes ++back to a number (if the underlying type is known to be a number). ++ ++This entry can be used to store a C structure (the number ++of bytes to be copied is calculated using the C C function) ++and can be used as an alternative to T_PTRREF without having to worry ++about a memory leak (since Perl will clean up the SV). ++ ++=item T_OPAQUE ++ ++This can be used to store data from non-pointer types in the string ++part of an SV. It is similar to T_OPAQUEPTR except that the ++typemap retrieves the pointer directly rather than assuming it ++is being supplied. For example, if an integer is imported into ++Perl using T_OPAQUE rather than T_IV the underlying bytes representing ++the integer will be stored in the SV but the actual integer value will ++not be available. i.e. The data is opaque to perl. ++ ++The data may be retrieved using the C function if the ++underlying type of the byte stream is known. ++ ++T_OPAQUE supports input and output of simple types. ++T_OPAQUEPTR can be used to pass these bytes back into C if a pointer ++is acceptable. ++ ++=item Implicit array ++ ++xsubpp supports a special syntax for returning ++packed C arrays to perl. If the XS return type is given as ++ ++ array(type, nelem) ++ ++xsubpp will copy the contents of C bytes from ++RETVAL to an SV and push it onto the stack. This is only really useful ++if the number of items to be returned is known at compile time and you ++don't mind having a string of bytes in your SV. Use T_ARRAY to push a ++variable number of arguments onto the return stack (they won't be ++packed as a single string though). ++ ++This is similar to using T_OPAQUEPTR but can be used to process more ++than one element. ++ ++=item T_PACKED ++ ++Calls user-supplied functions for conversion. For C ++(XSUB to Perl), a function named C is called ++with the output Perl scalar and the C variable to convert from. ++C<$ntype> is the normalized C type that is to be mapped to ++Perl. Normalized means that all C<*> are replaced by the ++string C. The return value of the function is ignored. ++ ++Conversely for C (Perl to XSUB) mapping, the ++function named C is called with the input Perl ++scalar as argument and the return value is cast to the mapped ++C type and assigned to the output C variable. ++ ++An example conversion function for a typemapped struct ++C might be: ++ ++ static void ++ XS_pack_foo_tPtr(SV *out, foo_t *in) ++ { ++ dTHX; /* alas, signature does not include pTHX_ */ ++ HV* hash = newHV(); ++ hv_stores(hash, "int_member", newSViv(in->int_member)); ++ hv_stores(hash, "float_member", newSVnv(in->float_member)); ++ /* ... */ ++ ++ /* mortalize as thy stack is not refcounted */ ++ sv_setsv(out, sv_2mortal(newRV_noinc((SV*)hash))); ++ } ++ ++The conversion from Perl to C is left as an exercise to the reader, ++but the prototype would be: ++ ++ static foo_t * ++ XS_unpack_foo_tPtr(SV *in); ++ ++Instead of an actual C function that has to fetch the thread context ++using C, you can define macros of the same name and avoid the ++overhead. Also, keep in mind to possibly free the memory allocated by ++C. ++ ++=item T_PACKEDARRAY ++ ++T_PACKEDARRAY is similar to T_PACKED. In fact, the C (Perl ++to XSUB) typemap is identical, but the C typemap passes ++an additional argument to the C function. This ++third parameter indicates the number of elements in the output ++so that the function can handle C arrays sanely. The variable ++needs to be declared by the user and must have the name ++C where C<$ntype> is the normalized C type name ++as explained above. The signature of the function would be for ++the example above and C: ++ ++ static void ++ XS_pack_foo_tPtrPtr(SV *out, foo_t *in, UV count_foo_tPtrPtr); ++ ++The type of the third parameter is arbitrary as far as the typemap ++is concerned. It just has to be in line with the declared variable. ++ ++Of course, unless you know the number of elements in the ++C C array, within your XSUB, the return value from ++C will be hard to decipher. ++Since the details are all up to the XS author (the typemap user), ++there are several solutions, none of which particularly elegant. ++The most commonly seen solution has been to allocate memory for ++N+1 pointers and assign C to the (N+1)th to facilitate ++iteration. ++ ++Alternatively, using a customized typemap for your purposes in ++the first place is probably preferable. ++ ++=item T_DATAUNIT ++ ++NOT YET ++ ++=item T_CALLBACK ++ ++NOT YET ++ ++=item T_ARRAY ++ ++This is used to convert the perl argument list to a C array ++and for pushing the contents of a C array onto the perl ++argument stack. ++ ++The usual calling signature is ++ ++ @out = array_func( @in ); ++ ++Any number of arguments can occur in the list before the array but ++the input and output arrays must be the last elements in the list. ++ ++When used to pass a perl list to C the XS writer must provide a ++function (named after the array type but with 'Ptr' substituted for ++'*') to allocate the memory required to hold the list. A pointer ++should be returned. It is up to the XS writer to free the memory on ++exit from the function. The variable C is set to the number ++of elements in the new array. ++ ++When returning a C array to Perl the XS writer must provide an integer ++variable called C containing the number of elements in the ++array. This is used to determine how many elements should be pushed ++onto the return argument stack. This is not required on input since ++Perl knows how many arguments are on the stack when the routine is ++called. Ordinarily this variable would be called C. ++ ++Additionally, the type of each element is determined from the type of ++the array. If the array uses type C xsubpp will ++automatically work out that it contains variables of type C and ++use that typemap entry to perform the copy of each element. All ++pointer '*' and 'Array' tags are removed from the name to determine ++the subtype. ++ ++=item T_STDIO ++ ++This is used for passing perl filehandles to and from C using ++C structures. ++ ++=item T_INOUT ++ ++This is used for passing perl filehandles to and from C using ++C structures. The file handle can used for reading and ++writing. This corresponds to the C<+E> mode, see also T_IN ++and T_OUT. ++ ++See L for more information on the Perl IO abstraction ++layer. Perl must have been built with C<-Duseperlio>. ++ ++There is no check to assert that the filehandle passed from Perl ++to C was created with the right C mode. ++ ++Hint: The L tutorial covers the T_INOUT, T_IN, and T_OUT ++XS types nicely. ++ ++=item T_IN ++ ++Same as T_INOUT, but the filehandle that is returned from C to Perl ++can only be used for reading (mode C>). ++ ++=item T_OUT ++ ++Same as T_INOUT, but the filehandle that is returned from C to Perl ++is set to use the open mode C<+E>. ++ ++=back ++ +diff --git a/t/XSTest.xs b/t/XSTest.xs +index 89df22f..452d3db 100644 +--- a/t/XSTest.xs ++++ b/t/XSTest.xs +@@ -76,6 +76,7 @@ bool + T_BOOL_2(in) + bool in + CODE: ++ PERL_UNUSED_VAR(RETVAL); + OUTPUT: in + + void +diff --git a/t/XSUsage.xs b/t/XSUsage.xs +index 9a8d93d..ed3c8f8 100644 +--- a/t/XSUsage.xs ++++ b/t/XSUsage.xs +@@ -35,6 +35,8 @@ xsusage_two() + ALIAS: + two_x = 1 + FOO::two = 2 ++ INIT: ++ PERL_UNUSED_VAR(ix); + + int + interface_v_i() +-- +2.14.3 + diff --git a/perl-ExtUtils-ParseXS.spec b/perl-ExtUtils-ParseXS.spec index 7708011..27ff7e2 100644 --- a/perl-ExtUtils-ParseXS.spec +++ b/perl-ExtUtils-ParseXS.spec @@ -7,6 +7,8 @@ Summary: Module and a script for converting Perl XS code into C code License: GPL+ or Artistic URL: http://search.cpan.org/dist/ExtUtils-ParseXS/ Source0: http://www.cpan.org/authors/id/S/SM/SMUELLER/ExtUtils-ParseXS-%{version}.tar.gz +# Unbundled from perl 5.28.0-RC1 +Patch0: ExtUtils-ParseXS-3.35-Upgrade-to-3.39.patch BuildArch: noarch BuildRequires: coreutils BuildRequires: make @@ -48,6 +50,7 @@ the glue necessary to let Perl access those functions. %prep %setup -q -n ExtUtils-ParseXS-%{version} +%patch0 -p1 %build perl Makefile.PL INSTALLDIRS=vendor NO_PACKLIST=1 @@ -71,6 +74,9 @@ make test %{_mandir}/man3/* %changelog +* Thu May 24 2018 Jitka Plesnikova - 1:3.39-1 +- Upgrade to 3.39 as provided in perl-5.28.0-RC1 + * Thu Feb 08 2018 Fedora Release Engineering - 1:3.35-2 - Rebuilt for https://fedoraproject.org/wiki/Fedora_28_Mass_Rebuild