592 lines
26 KiB
Diff
592 lines
26 KiB
Diff
From e911aae9c4474cc16d06be02fabcacde9f8d54b5 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Jan=20Pokorn=C3=BD?= <jpokorny@redhat.com>
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Date: Fri, 6 Oct 2017 17:17:26 +0200
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Subject: [PATCH 5/6] High: bare fix for libqb logging not working with
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ld.bfd/binutils 2.29+
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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(or rather [read on]: "bare" fix)
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Initially with the help of the internal test suite and the failing log
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test, it was eventually discovered[1] that these binutils commits going
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to the recent 2.29 release affected the treatment of _start_SECNAME
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and __stop_SECNAME symbols denoting the boundary start/stop addresses
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of a SECNAME orphan section -- specifically in libqb context a custom
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section (SECNAME=__verbose) used for link-time ("run-time amortizing")
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callsite collection when there's a support in the toolchain[*]:
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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=cbd0eecf261c2447781f8c89b0d955ee66fae7e9
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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b27685f2016c510d03ac9a64f7b04ce8efcf95c4
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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=7dba9362c172f1073487536eb137feb2da30b0ff
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The first one explicitly states:
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> Also __start_SECNAME and __stop_SECNAME symbols are marked as hidden
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> by ELF linker so that __start_SECNAME and __stop_SECNAME symbols for
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> section SECNAME in different modules are unique.
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The problem is that libqb silently depends on the previous status quo
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ld.bfd linker behaviour of keeping those symbols externally visible,
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which was apparently not granted as it has deliberately changed per
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above.
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And then for 2.29.1 release of binutils once again, as someone actually
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noticed something went overboard with the 2.29 changes:
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http://lists.gnu.org/archive/html/bug-binutils/2017-08/msg00195.html
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(overview of the original bug discussion, rather than directly
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https://sourceware.org/bugzilla/show_bug.cgi?id=21964, which is
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a result of a conflct resolution when restoring bugzilla backup)
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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=487b6440dad57440939fab7afdd84a218b612796
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At least that change doesn't invalidate all the effort being put into
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the original version of the changeset, only the configure script check
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had to be refined so as not to miss the "orphan section magic not
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working properly out of the box, without a bandaid" observation
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(see the inline comment) -- the workaround arrangement needs
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to be applied in that case as well.
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* * *
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So regarding the solution itself, the core of the fix was sketched at
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the original Fedora targeted bug against binutils[2]. In short, we are
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using a custom linker script that (re)describes the mentioned custom
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orphan output section, or better yet, assuredly pushes that section,
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and more importantly, it's own boundary denoting symbols, through into
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the resulting binary when it's being linked (as in compile-time step).
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This solution alone, while working for the non-libqb (more on that
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below) logging participants, is not good enough, as it requires all
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libqb targets to start using new incantation (namely "-Wl,foo.t" switch)
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in the final link step during compilation, which might be solvable
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with a tweak in libqb's pkg-config file under assumption that practice
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of using "pkg-config --libs libqb" is rigidly followed. Which is likely
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a false expectation, and furthermore only for the regular consumption
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model, as it doesn't cover the least bit the developmental one (refer
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to previous-but-one "tests" commit message), e.g. applied for internal
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examples + tests (but no local sub-checkout tree usage can be excluded).
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So further extensions were devised to cover both consumption models:
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- a. regular:
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courtesy of binutils maintainer[3], we follow an idea to make libqb.so
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(i.e. what the targets link against) rather a linker script on its
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own, which first include the version-specified (e.g. libqb.so.0) file
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into the link, then lists, in situ, the content of the linker script
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per above, hence -lqb linking has the same effect as having both
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"-lqb -Wl,foo.t" explicitly in the link command prior to this trick
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- b. developmental:
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to eliminate any kind of race condition arising from the attempt
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to post-modify libqb.la libtool archive file generated internally
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by libtool, we sort of abuse "inherited_linker_flags" variable
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within this file format, as it forms an accumulative value across
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the whole transitive dependencies chain (if not impaired per the
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note below), fitting exactly our purpose of injecting "-Wl,foo.t"
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switch equivalent for those libtool-linking by L{D,IB}ADD'ing
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libqb.la; it's then enough to craft a custom libtool archive file
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declaring that value, and hook it into such dependency chain through
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libqb_la_LIBADD, and with a little bit of further fiddling, it works
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as desired (note that double occurrence of "-Wl,foo.t" equivalent
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present at some stages of sorting this trick turned out to be,
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surprisingly, counter-productive, which should now demistify the
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very existence of effectively empty qblog_script_noop.ld file);
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NOTE: some forms of libtool distribution (debian + derivatives ones
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in particular) undermine natural transitive dependency propagation
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with a deliberate cut off (https://bugs.debian.org/702737), so we
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need to ensure the "impairment" is not happening by force (corosync
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precedent: https://github.com/corosync/corosync/commit/0f1dc5c1)
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^ something like this needs to be applied for any such "private
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consumer" (although it hopefully goes without saying this way
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of consuming libqb outside of it's own playground is hardly
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the Right Thing) if portability is important, nonetheless!
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On the address of linker script workaround, there are linkers out there
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that do not support the trick, for instance:
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- ld.gold from binutils (but it has hardly ever been working with
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orphan sections, anyway:
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https://sourceware.org/bugzilla/show_bug.cgi?id=22291)
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- ancient versions of ld.bfd, e.g. 10+ years old one used as a native
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system linker even in the most recent releases of FreeBSD, unless
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GCC toolchain is used instead
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If these are hit when (because) the compiler has already demonstrated it
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supports section attribute, the build system configuration is forcibly
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stopped, simply to stay conceptually compatible with the prior state in
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which the affinity to leverage that feature hasn't been called off
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under any circumstances. One is, however, able to achieve exactly
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this behaviour with --enable-nosection-fallback switch, but if some
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other participants in the logging, possibly linked with a more friendly
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linker, do utilize this orphan section, logging may silently break
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(another reason to require an explicit sign-off).
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Last but not least, libqb itself needs to be linked with the mentioned
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"-Wl,foo.t" equivalent for its own outgoing log messages to be honoured
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under all circumstances, which is already achieved with the arrangement
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for b. above, and by experiments, further redefinition of those boundary
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denoting symbols as weak was necessary so as to make them truly global
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within libqb.so proper (at least with binutils 2.29).
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* * *
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Finally, let's have a look how the already well-known test matrix
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overview changes as of this commit, but first as a recap,
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"X(Y)" denotes "X linked with linker Y":
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X(a) .. ld.bfd < 2.29
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X(b) .. ld.bfd = 2.29 (+ 2.29.1 and hopefully on)
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and here you are (values in <angle brackets> denote non-trivial change
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[not mere rewording] introduced as of this commit, in comparison to the
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table stated in the preceding commit):
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+=========+=========+=========+=========+=========+=========+=========+
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#client(x)# libqb(a) usage # libqb(b) usage #
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# vvv #---------+---------+---------+---------+---------+---------+
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# V # direct | libX(a) : libX(b) # direct | libX(a) : libX(b) #
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+=========+=========+=========+=========+=========+=========+=========+
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# x = a # OK | OK : <OK> # <OK> | <OK> : <OK> #
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# x = b # <OK> | <OK> : <OK> # <OK> | <OK> : <OK> #
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+=========+=========+=========+=========+=========+=========+=========+
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Everything is green \o/
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Note: as of this fix, it is assumed that the non-green counterpart of
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this table in the message for the preceding commit doubles as an
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indicator how will mixing the logging participants wrt. linker+libqb
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version work out, when "X(Y)" becomes read as "X linked with linker
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Y under additional restriction on libqb version when compile-time link
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is performed of the particular part":
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X(a) .. ld.bfd < 2.29 OR [arbitrary ld.bfd AND libqb after this fix)
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X(b) .. ld.bfd = 2.29 (and likely on) AND libqb up to, but excluding
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this fix
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* * *
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Let's also state some imperfections and loops kept open:
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Deficiencies:
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* whenever anything is compiled against our install-time-modified
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libqb.so so as to force the visibility of the discussed symbols
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(or when compiling [with] libqb internally):
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> /usr/bin/ld: warning: ../lib/qblog_script.ld contains output sections; did you forget -T?
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- not solvable as long as we use the linker script, and there's
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hardly any other way not requiring the libqb consumers to adapt
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in any aspect
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Open questions:
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* what about binutils 2.99.1 partially mitigating the impact of the
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above commits
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* should we enable attribute((__section__)) for powerpc platforms?
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it seems to work well there -- and related to that, we need to figure
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out how static and dynamic call sites can live together -- say what
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will happen to logging programs compiled with libqb w/o attribute
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sections when the underlying libqb is flipped to the one with them...
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* * *
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[*] basically GCC's section("SECNAME") __attribute__ annotation of the
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global variables + linker described behaviour previously mistakenly
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taken for granted
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References:
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[1] http://oss.clusterlabs.org/pipermail/developers/2017-July/000503.html
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[2] https://bugzilla.redhat.com/show_bug.cgi?id=1477354#c2 + comment 8
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[3] https://bugzilla.redhat.com/show_bug.cgi?id=1477354#c9
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Signed-off-by: Jan Pokorný <jpokorny@redhat.com>
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---
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configure.ac | 146 +++++++++++++++++++++++++++++++++++++++++------
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lib/Makefile.am | 67 ++++++++++++++++++++++
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lib/libqb.pc.in | 6 ++
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lib/log.c | 7 +++
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lib/qblog_script.la.in | 15 +++++
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lib/qblog_script.ld.in | 25 ++++++++
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lib/qblog_script_noop.ld | 1 +
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7 files changed, 249 insertions(+), 18 deletions(-)
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create mode 100644 lib/qblog_script.la.in
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create mode 100644 lib/qblog_script.ld.in
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create mode 100644 lib/qblog_script_noop.ld
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diff --git a/configure.ac b/configure.ac
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index 5769e60..57875c8 100644
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--- a/configure.ac
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+++ b/configure.ac
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@@ -501,6 +501,14 @@ AC_ARG_ENABLE([debug],
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AC_ARG_ENABLE([coverage],
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[AS_HELP_STRING([--enable-coverage],[coverage analysis of the codebase])])
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+AC_ARG_ENABLE([interlib-deps],
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+ [AS_HELP_STRING([--disable-interlib-deps],
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+ [disable inter-library dependencies (might break builds)])])
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+
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+AC_ARG_ENABLE([nosection-fallback],
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+ [AS_HELP_STRING([--enable-nosection-fallback],
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+ [allow (logging compat-breaking?) fallback when orphan section dead-ended])])
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+
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AC_ARG_ENABLE([slow-tests],
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[AS_HELP_STRING([--enable-slow-tests],[build and run slow tests])])
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@@ -609,6 +617,19 @@ else
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COVERAGE_LDFLAGS=""
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fi
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+# --- inter-library dependencies ---
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+# because of debian/ubuntu swimming against the stream
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+# https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=702737,
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+# override the libtool variable by force because the current
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+# arrangement relies on transitive dependency propagation
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+AC_MSG_NOTICE([Enabling inter-library dependencies: $enable_interlib_deps])
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+if test "x${enable_interlib_deps}" = xno; then
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+ link_all_deplibs=no
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+else
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+ link_all_deplibs=yes
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+fi
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+
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+# --- slow tests ---
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if test "x${enable_slow_tests}" = xyes ; then
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AC_DEFINE([HAVE_SLOW_TESTS], 1,[have slow tests])
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AC_MSG_NOTICE([Enabling Slow tests])
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@@ -618,33 +639,120 @@ AC_SUBST(HAVE_SLOW_TESTS)
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# --- callsite sections ---
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if test "x${GCC}" = xyes; then
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+ AX_SAVE_FLAGS
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AC_MSG_CHECKING([whether GCC supports __attribute__((section()) + ld supports orphan sections])
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if test "x${ac_cv_link_attribute_section}" = x ; then
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- AC_TRY_RUN(
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- AC_LANG_PROGRAM(
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+ LDFLAGS="${LDFLAGS_save} -shared -fPIC" # we are compiling shared lib
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+ AC_LINK_IFELSE(
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+ [AC_LANG_SOURCE(
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[[#include <assert.h>
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- extern void * __start___verbose, * __stop___verbose;]],
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- [[static int my_var __attribute__((section("__verbose"))) = 5;
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- assert("non-empty data section"
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- && __start___verbose != __stop___verbose);
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- assert("no data section value loss"
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- && my_var == 5);]]
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- ),
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- [gcc_has_attribute_section=yes],
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+ extern int __start___verbose[], __stop___verbose[];
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+ int test(void) {
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+ static int my_var __attribute__((section("__verbose"))) = 3;
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+ assert("L:non-empty data section"
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+ && __start___verbose != __stop___verbose);
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+ assert("L:no data section value loss"
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+ && my_var == 3 /* for 2.29.1+ */);
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+ return *((int *) __start___verbose); }]]
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+ )],
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+ [gcc_has_attribute_section=yes; cp "conftest${EXEEXT}" "conftest.so"],
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[gcc_has_attribute_section=no]
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)
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+ AX_RESTORE_FLAGS
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else
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gcc_has_attribute_section=${ac_cv_link_attribute_section}
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fi
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-
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AC_MSG_RESULT($gcc_has_attribute_section)
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- if test $gcc_has_attribute_section = yes; then
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- AC_DEFINE([QB_HAVE_ATTRIBUTE_SECTION], 1,
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- [Enabling code using __attribute__((section))])
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- PACKAGE_FEATURES="$PACKAGE_FEATURES attribute-section"
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- AC_SUBST([client_dlopen_LIBS],[$dlopen_LIBS])
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+
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+ # in the failing case (e.g. with ld from binutils 2.29), it's likely the
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+ # following will fail readily in linkage (hidden symbol `__stop___verbose'
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+ # in conftest is referenced by DSO), but keep the sensible test (in-binary
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+ # symbol is expected to be propagated into the library, and to draw the
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+ # full circle back to binary through standard return value passing;
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+ # -rpath passed because LD_LIBRARY_PATH exporting is unwieldy here);
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+ # moreover, "my_var" == 3 assertion above is necessary so that binutils
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+ # 2.29.1+ will not slip other parts of the overall is-workaround-needed
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+ # harness, as it restored some (but not all) of the original behaviour,
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+ # but the workaround is still provably needed
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+ if test "x${gcc_has_attribute_section}" = xyes; then
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+ AC_MSG_CHECKING([whether linker emits global boundary symbols for orphan sections])
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+ LIBS="${LIBS} -L. -l:conftest.so -Wl,-rpath=$(pwd)"
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+ AC_TRY_RUN(
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+ AC_LANG_PROGRAM(
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+ [[#include <assert.h>
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+ extern int __start___verbose[], __stop___verbose[];
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+ int test(void);]],
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+ [[static int my_var __attribute__((section("__verbose"))) = 5;
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+ assert("P:non-empty data section"
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+ && __start___verbose != __stop___verbose);
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+ assert("P:no data section value loss"
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+ && my_var == test() /*5?*/);]]
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+ ),
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+ [gcc_has_attribute_section_visible=yes],
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+ [gcc_has_attribute_section_visible=no]
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+ )
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+ AX_RESTORE_FLAGS
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+ AC_MSG_RESULT($gcc_has_attribute_section_visible)
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+ rm -f "conftest.so"
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+
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+ if test "x${gcc_has_attribute_section_visible}" = xno; then
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+ # check if the linker script based workaround is
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+ # feasible at all, otherwise fallback to using no
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+ # section attribute while making some noise about it
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+ # as combining with-without accustomed logging
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+ # participants is currently uncharted waters
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+ AC_MSG_CHECKING([whether linker workaround for orphan sections usable])
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+ >conftest.ld cat <<-EOF
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+ SECTIONS {
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+ __verbose : {
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+ __start___verbose = .;
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+ *(__verbose);
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+ __stop___verbose = .;
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+ }
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+ }
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+ EOF
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+ LDFLAGS="${LDFLAGS} -Wl,conftest.ld"
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+ AC_LINK_IFELSE(
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+ [AC_LANG_PROGRAM(
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+ [[#include <assert.h>
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+ extern int __start___verbose[], __stop___verbose[];
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+ int test(void);]],
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+ [[static int my_var __attribute__((section("__verbose"))) = 5;
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+ assert("P:non-empty data section"
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+ && __start___verbose != __stop___verbose);
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+ assert("P:no data section value loss"
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+ && my_var == 5);]]
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+ )],
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+ [],
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+ [gcc_has_attribute_section=no]
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+ )
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+ AX_RESTORE_FLAGS
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+ AC_MSG_RESULT([$gcc_has_attribute_section])
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+ rm -f "conftest.ld"
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+ fi
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+
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+ if test "x${gcc_has_attribute_section}" = xyes; then
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+ AC_DEFINE([QB_HAVE_ATTRIBUTE_SECTION], 1,
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+ [Enabling code using __attribute__((section))])
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+ AC_SUBST([client_dlopen_LIBS],[$dlopen_LIBS])
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+ if test "x${gcc_has_attribute_section_visible}" = xyes; then
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+ PACKAGE_FEATURES="$PACKAGE_FEATURES attribute-section"
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+ else
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+ AC_DEFINE([QB_NEED_ATTRIBUTE_SECTION_WORKAROUND], 1,
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+ [Enabling code using __attribute__((section))])
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+ PACKAGE_FEATURES="$PACKAGE_FEATURES attribute-section-workaround"
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+ fi
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+ elif test "x${enable_nosection_fallback}" = xyes; then
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+ AC_MSG_NOTICE([Falling back to not using orphan section])
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+ else
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+ AC_MSG_ERROR([Would use section attribute, cannot; see --enable-nosection-fallback])
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+ fi
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fi
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fi
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+AM_CONDITIONAL(HAVE_GCC_ATTRIBUTE_SECTION, [test "x${gcc_has_attribute_section}" = xyes])
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+AM_CONDITIONAL(NEED_GCC_ATTRIBUTE_SECTION_WORKAROUND,
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+ [test "x${gcc_has_attribute_section}" = xyes \
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+ && test "x${gcc_has_attribute_section_visible}" != xyes])
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# --- ansi ---
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if test "x${enable_ansi}" = xyes && \
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@@ -726,9 +834,11 @@ AC_CONFIG_FILES([Makefile
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docs/Makefile
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docs/common.dox
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docs/html.dox
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- docs/man.dox])
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+ docs/man.dox
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+ lib/qblog_script.la:lib/qblog_script.la.in])
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-AC_CONFIG_LINKS([tests/functional/GNUmakefile:tests/functional/GNUmakefile])
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+AC_CONFIG_LINKS([lib/qblog_script_noop.ld:lib/qblog_script_noop.ld
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+ tests/functional/GNUmakefile:tests/functional/GNUmakefile])
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AC_OUTPUT
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diff --git a/lib/Makefile.am b/lib/Makefile.am
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index 0bebeb5..ff5b3b4 100644
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--- a/lib/Makefile.am
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+++ b/lib/Makefile.am
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@@ -19,6 +19,7 @@
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# along with libqb. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
|
|
+CLEANFILES = qblog_script.ld
|
|
MAINTAINERCLEANFILES = Makefile.in
|
|
|
|
noinst_HEADERS = ipc_int.h util_int.h ringbuffer_int.h loop_int.h \
|
|
@@ -39,9 +40,48 @@ source_to_lint = util.c hdb.c ringbuffer.c ringbuffer_helper.c \
|
|
log_syslog.c log_dcs.c log_format.c \
|
|
map.c skiplist.c hashtable.c trie.c
|
|
|
|
+# Following two files related to linkage using classic ld from binutils 2.29+
|
|
+# with which we cannot afford to lose public access to section boundary symbols
|
|
+# (as the mentioned version started to scope them privately by default, see
|
|
+# the comment within the first of the files, ultimately leading to broken
|
|
+# logging functionality of libqb) deserve a bit of explanation:
|
|
+# * qblog_script.ld
|
|
+# - linker script that instructs the output section that those symbols should
|
|
+# be visible, i.e. supports the same behaviour regardless of ld version
|
|
+# - serves two purposes:
|
|
+# . local: libqb itself and its "private" (cf. examples) users need those
|
|
+# symbols visible, which is achieved with a help of the other file
|
|
+# . system-wide: whenever the non-private library users link against libqb
|
|
+# (it's development files), this linker script with
|
|
+# prepended INPUT command so as to refer to the actual
|
|
+# libqb library (it's numbered alias that is eventually
|
|
+# resolved to proper shared library) is masked as libqb.so,
|
|
+# this arrangement achieves the libqb's user will have
|
|
+# the discussed symbols visible alike
|
|
+# * qblog_script.la
|
|
+# - as mentioned earlier, this indirectly hooks into libtool machinery, with
|
|
+# the only true intention of injecting "-Wl,<path to qblog_script.ld>"
|
|
+# into "inherited_linker_flags" libtool archive variable, from where it's
|
|
+# subsequently spread into the build process of all the internal library
|
|
+# users, assuming they have their dep arranged as "user_LIBADD=libqb.la"
|
|
+# (this also alleviates the burden on getting things right if, e.g., any
|
|
+# libqb user consumes it directly like this from its own sub-checkout tree)
|
|
+# - it indirectly, once libtool prechew the original link command
|
|
+# originally referring to this file, it turns such reference into the
|
|
+# "real" library reference (here combining libdir and old_library
|
|
+# variables within the file), also ensures libqb itself will visibly
|
|
+# expose the discussed symbols, because such references point again to
|
|
+# the (not enriched) linker script file that will get interpreted just
|
|
+# like that during the last build step of the library
|
|
+EXTRA_libqb_la_DEPENDENCIES = qblog_script.ld qblog_script.la
|
|
+EXTRA_DIST = qblog_script.ld.in qblog_script.la.in qblog_script_noop.ld
|
|
+
|
|
libqb_la_SOURCES = $(source_to_lint) unix.c
|
|
libqb_la_CFLAGS = $(PTHREAD_CFLAGS)
|
|
libqb_la_LIBADD = $(LTLIBOBJS) $(dlopen_LIBS) $(PTHREAD_LIBS) $(socket_LIBS)
|
|
+if NEED_GCC_ATTRIBUTE_SECTION_WORKAROUND
|
|
+libqb_la_LIBADD += qblog_script.la
|
|
+endif
|
|
|
|
AM_LDFLAGS = $(LDFLAGS_COPY:-Bsymbolic-functions=)
|
|
|
|
@@ -60,6 +100,33 @@ else
|
|
endif
|
|
endif
|
|
|
|
+qblog_script.ld: %.ld: %.ld.in
|
|
+ $(AM_V_GEN)$(CPP) -xc -I$(top_srcdir)/include -D_GNU_SOURCE -C -P $< \
|
|
+ | sed -n "/$$(sed -n '/^[^#]/{s/[*\/]/\\&/g;p;q;}' $<)/,$$ p" \
|
|
+ > $@
|
|
+
|
|
+# find the libqb.so symlink's target, if so, try to find out, iteratively,
|
|
+# its gradually shorter forms that likewise symlinks the same target as the
|
|
+# original libqb.so path, point to that file from the linker script using
|
|
+# qblog_script.ld as a template, storing result in place of original libqb.so
|
|
+# (e.g., libqb.so := "INPUT(libqb.so.0) " [...] "SECTIONS { " [...] "}")
|
|
+# NOTE: readlink nor realpath are POSIX; not chained links ready
|
|
+# NOTE: conservative check, i.e., not per NEED_GCC_ATTRIBUTE_SECTION_WORKAROUND
|
|
+if HAVE_GCC_ATTRIBUTE_SECTION
|
|
+install-exec-hook: qblog_script.ld
|
|
+ target=$$(ls -l "$(DESTDIR)$(libdir)/libqb.so" || :); \
|
|
+ target=$${target#* -> }; t1_bn=$$(basename "$${target}" || :); \
|
|
+ while test -n "$${t1_bn}"; do t2_bn=$${t1_bn%.*[0-9]*}; \
|
|
+ test "$${t2_bn}" != libqb.so || break; \
|
|
+ test -L "$${t2_bn}" || { t1_bn=$${t2_bn}; continue; }; \
|
|
+ t2_target=$$(ls -l "$${t2_bn}" || break); t2_target=$${t2_target#* -> }; \
|
|
+ test "$${t2_target}" = "$${target}" || break; \
|
|
+ t1_bn=$${t2_bn}; done; test -n "$${t1_bn}" || \
|
|
+ { echo "only applicable to SO symlink scheme"; exit 1; }; \
|
|
+ echo "INPUT($${t1_bn})" > "$(DESTDIR)$(libdir)/libqb.so-t"
|
|
+ cat $< >> "$(DESTDIR)$(libdir)/libqb.so-t"
|
|
+ mv -f "$(DESTDIR)$(libdir)/libqb.so-t" "$(DESTDIR)$(libdir)/libqb.so"
|
|
+endif
|
|
|
|
pkgconfigdir = $(libdir)/pkgconfig
|
|
pkgconfig_DATA = libqb.pc
|
|
diff --git a/lib/libqb.pc.in b/lib/libqb.pc.in
|
|
index 37d27b7..bdcd3c8 100644
|
|
--- a/lib/libqb.pc.in
|
|
+++ b/lib/libqb.pc.in
|
|
@@ -8,5 +8,11 @@ Version: @PACKAGE_VERSION@
|
|
Description: libqb
|
|
Requires:
|
|
Libs: -L${libdir} -lqb @client_dlopen_LIBS@
|
|
+# NOTE: If -lqb not usable for linking (e.g. linker not compatible with
|
|
+# linker scripts ad-hoc modifying output sections), try recent
|
|
+# ld.bfd/binutils linker first when available, otherwise you can
|
|
+# try "-l:libqb.so.<digit>" link switch (right <digit> available,
|
|
+# for example, directly within libqb.so plaintext) that bypasses
|
|
+# said linker script -- but beware, logging problems may ensue.
|
|
Libs.private: @LIBS@
|
|
Cflags: -I${includedir}
|
|
diff --git a/lib/log.c b/lib/log.c
|
|
index f30b8d8..e4b77d5 100644
|
|
--- a/lib/log.c
|
|
+++ b/lib/log.c
|
|
@@ -40,6 +40,13 @@
|
|
#include "util_int.h"
|
|
#include <regex.h>
|
|
|
|
+#if defined(QB_NEED_ATTRIBUTE_SECTION_WORKAROUND) && !defined(S_SPLINT_S)
|
|
+/* following only needed to force these symbols be global
|
|
+ with ld 2.29: https://bugzilla.redhat.com/1477354 */
|
|
+struct qb_log_callsite __attribute__((weak)) QB_ATTR_SECTION_START[] = { 0 };
|
|
+struct qb_log_callsite __attribute__((weak)) QB_ATTR_SECTION_STOP[] = { 0 };
|
|
+#endif
|
|
+
|
|
static struct qb_log_target conf[QB_LOG_TARGET_MAX];
|
|
static uint32_t conf_active_max = 0;
|
|
static int32_t in_logger = QB_FALSE;
|
|
diff --git a/lib/qblog_script.la.in b/lib/qblog_script.la.in
|
|
new file mode 100644
|
|
index 0000000..f262df8
|
|
--- /dev/null
|
|
+++ b/lib/qblog_script.la.in
|
|
@@ -0,0 +1,15 @@
|
|
+# Generated by libtool
|
|
+# NOTE: above line is just to pass func_ltwrapper_script_p sanity check of
|
|
+# libtool script, as we are basically sort of abusing it so as to inject
|
|
+# our custom linker script to "private" (cf. examples) users of libqb.la
|
|
+
|
|
+# shall rather carry a location of old_library (possibly libdir or something
|
|
+# else, but installed=no needed to suppress 'library moved' warning then) as
|
|
+# it's together (with libtool implied prefix otherwise) used for linking libqb
|
|
+libdir=@abs_builddir@
|
|
+
|
|
+# avoids issues with library_names (spurious rpath emitting, relink-on-install)
|
|
+old_library=qblog_script_noop.ld
|
|
+
|
|
+# subject of our injection into libqb.la impacting build time for private users
|
|
+inherited_linker_flags=-Wl,@abs_builddir@/qblog_script.ld
|
|
diff --git a/lib/qblog_script.ld.in b/lib/qblog_script.ld.in
|
|
new file mode 100644
|
|
index 0000000..fed826b
|
|
--- /dev/null
|
|
+++ b/lib/qblog_script.ld.in
|
|
@@ -0,0 +1,25 @@
|
|
+#include <qb/qblog.h>
|
|
+/* GNU ld script
|
|
+ This atypical arrangement enforces global visibility of boundary symbols
|
|
+ (QB_ATTR_SECTION_START, QB_ATTR_SECTION_STOP) for the custom section
|
|
+ QB_ATTR_SECTION used for compile-time offloading of the logging call sites
|
|
+ tracking. While libqb relies on these being global, default linker from
|
|
+ binutils change the visibility as of version 2.29, making the logging
|
|
+ unusable without artificial stimulus: https://bugzilla.redhat.com/1477354
|
|
+
|
|
+ NOTE: If -lqb not usable for linking (e.g. linker not compatible with
|
|
+ linker scripts ad-hoc modifying output sections), try recent
|
|
+ ld.bfd/binutils linker first when available, otherwise you can
|
|
+ try "-l:libqb.so.<digit>" link switch (right <digit> available,
|
|
+ for example, directly within libqb.so plaintext) that bypasses
|
|
+ said linker script -- but beware, logging problems may ensue.
|
|
+ */
|
|
+SECTIONS {
|
|
+#ifdef QB_HAVE_ATTRIBUTE_SECTION
|
|
+ QB_ATTR_SECTION : {
|
|
+ QB_ATTR_SECTION_START = .;
|
|
+ *(QB_ATTR_SECTION);
|
|
+ QB_ATTR_SECTION_STOP = .;
|
|
+ }
|
|
+#endif
|
|
+}
|
|
diff --git a/lib/qblog_script_noop.ld b/lib/qblog_script_noop.ld
|
|
new file mode 100644
|
|
index 0000000..f037fca
|
|
--- /dev/null
|
|
+++ b/lib/qblog_script_noop.ld
|
|
@@ -0,0 +1 @@
|
|
+/* this is an empty linker script having a role of a NO-OP link object */
|
|
--
|
|
2.14.2
|
|
|