import redhat-rpm-config-190-1.el9

SOURCES/buildflags.md

@@ -13,6 +13,8 @@ this:
 
 This will invoke the `./configure` with arguments (such as
 `--prefix=/usr`) to adjust the paths to the packaging defaults.
+Prior to that, some common problems in autotools scripts are
+automatically patched across the source tree.
 
 As a side effect, this will set the environment variables `CFLAGS`,
 `CXXFLAGS`, `FFLAGS`, `FCFLAGS`, `LDFLAGS` and `LT_SYS_LIBRARY_PATH`,
@@ -25,7 +27,8 @@ environment variables using
     %set_build_flags
 
 early in the `%build` section.  (Again, existing environment variables
-are not overwritten.)
+are not overwritten.)  `%set_build_flags` does not perform autotools
+script rewriting, unlike `%configure`.
 
 Individual build flags are also available through RPM macros:
 
@@ -69,12 +72,70 @@ For other considerations involving shared objects, see:
 
 * [Fedora Packaging Guidelines: Shared Libraries](https://docs.fedoraproject.org/en-US/packaging-guidelines/#_shared_libraries)
 
-# Customizing compiler flags
+# Customizing compiler and other build flags
 
 It is possible to set RPM macros to change some aspects of the
 compiler flags.  Changing these flags should be used as a last
 recourse if other workarounds are not available.
 
+### Toolchain selection
+
+The default toolchain uses GCC, and the `%toolchain` macro is defined
+as `gcc`.
+
+It is enough to override `toolchain` macro and all relevant macro for C/C++
+compilers will be switched. Either in the spec or in the command-line.
+
+    %global toolchain clang
+
+or:
+
+    rpmbuild -D "toolchain clang" …
+
+Inside a spec file it is also possible to determine which toolchain is in use
+by testing the same macro. For example:
+
+    %if "%{toolchain}" == "gcc"
+    BuildRequires: gcc
+    %endif
+
+or:
+
+    %if "%{toolchain}" == "clang"
+    BuildRequires: clang compiler-rt
+    %endif
+
+### Disable autotools compatibility patching
+
+By default, the invocation of the `%configure` macro replaces
+`config.guess` files in the source tree with the system version.  To
+disable that, define this macro:
+
+    %global _configure_gnuconfig_hack 0
+
+`%configure` also patches `ltmain.sh` scripts, so that linker flags
+are set as well during libtool-.  This can be switched off using:
+
+    %global _configure_libtool_hardening_hack 0
+
+Further patching happens in LTO mode, see below.
+
+### Disabling Link-Time Optimization
+
+By default, builds use link-time optimization.  In this build mode,
+object code is generated at the time of the final link, by combining
+information from all available translation units, and taking into
+account which symbols are exported.
+
+To disable this optimization, include this in the spec file:
+
+   %define _lto_cflags %{nil}
+
+If LTO is enabled, `%configure` applies some common required fixes to
+`configure` scripts.  To disable that, define the RPM macro
+`_fix_broken_configure_for_lto` as `true` (sic; it has to be a shell
+command).
+
 ### Lazy binding
 
 If your package depends on the semantics of lazy binding (e.g., it has
@@ -116,6 +177,21 @@ recognized, so it has to come after the hardening flags on the command
 line (it has to be added at the end of `CFLAGS`, or specified after
 the `CFLAGS` variable contents).
 
+### Keeping dependencies on unused shared objects
+
+By default, ELF shared objects which are listed on the linker command
+line, but which have no referencing symbols in the preceding objects,
+are not added to the output file during the final link.
+
+In order to keep dependencies on shared objects even if none of
+their symbols are used, include this in the RPM spec file:
+
+    %undefine _ld_as_needed
+
+For example, this can be required if shared objects are used for their
+side effects in ELF constructors, or for making them available to
+dynamically loaded plugins.
+
 ### Strict symbol checks in the link editor (ld)
 
 Optionally, the link editor will refuse to link shared objects which
@@ -160,6 +236,72 @@ it is possible to add `-fcommon` to the flags by defining `%_legacy_common_suppo
 
 Properly fixing the failure is always preferred!
 
+### Post-build ELF object processing
+
+By default, DWARF debugging information is separated from installed
+ELF objects and put into `-debuginfo` subpackages.  To disable most
+debuginfo processing (and thus the generation of these subpackages),
+define `_enable_debug_packages` as `0`.
+
+Processing of debugging information is controlled using the
+`find-debuginfo` tool from the `debugedit` package.  Several aspects
+of its operation can be controlled at the RPM level.
+
+* Creation of `-debuginfo` subpackages is enabled by default.
+  To disable, undefine `_debuginfo_subpackages`.
+* Likewise, `-debugsource` subpackages are automatically created.
+  To disable, undefine `_debugsource_subpackages`.
+  See [Separate Subpackage and Source Debuginfo](https://fedoraproject.org/wiki/Changes/SubpackageAndSourceDebuginfo)
+  for background information.
+* `_build_id_links`, `_unique_build_ids`, `_unique_debug_names`,
+  `_unique_debug_srcs` control how debugging information and
+  corresponding source files are represented on disk.
+  See `/usr/lib/rpm/macros` for details.  The defaults
+  enable parallel installation of `-debuginfo` packages for
+  different package versions, as described in
+  [Parallel Installable Debuginfo](https://fedoraproject.org/wiki/Changes/ParallelInstallableDebuginfo).
+* By default, a compressed symbol table is preserved in the
+  `.gnu_debugdata` section.  To disable that, undefine
+  `_include_minidebuginfo`.
+* To speed up debuggers, a `.gdb_index` section is created.  It can be
+  disabled by undefining `_include_gdb_index`.
+* Missing build IDs result in a build failure.  To ignore such
+  problems, undefine `_missing_build_ids_terminate_build`.
+* During processing, build IDs are recomputed to match the binary
+  content.  To skip this step, define `_no_recompute_build_ids` as `1`.
+* By default, the options in `_find_debuginfo_dwz_opts` turn on `dwz`
+  (DWARF compression) processing.  Undefine this macro to disable this
+  step.
+* Additional options can be passed by defining the
+  `_find_debuginfo_opts` macro.
+
+After separation of debugging information, additional transformations
+are applied, most of them also related to debugging information.
+These steps can be skipped by undefining the corresponding macros:
+
+* `__brp_strip`: Removal of leftover debugging information.  The tool
+  specified by the `__strip` macro is invoked with the `-g` option on
+  ELF object (`.o`) files.
+* `__brp_strip_static_archive`: This is similar to `__brp_strip`, but
+  processes static `.a` archives instead.
+* `__brp_strip_comment_note`: This step removes unallocated `.note`
+  sections, and `.comment` sections from ELF files.
+* `__brp_strip_lto`: This step removes GCC LTO intermediate representation
+  in ELF sections starting with `.gnu.lto_` and `.gnu.debuglto_`.  Skipping
+  this step is strongly discouraged because the tight coupling of LTO
+  data with the GCC version.  The underlying tool is again determined by the
+  `__strip` macro.
+* `__brp_llvm_compile_lto_elf`: This step replaces LLVM bitcode files
+  with object files, thereby removing LLVM bitcode from the installed
+  files.  This transformation is applied to object files in static `.a`
+  archives, too.
+* `__brp_ldconfig`: For each shared object on the library search path
+  whose soname does not match its file name, a symbolic link from the
+  soname to the file name is created.  This way, these shared objects
+  are loadable immediately after installation, even if they are not yet
+  listed in the `/etc/ld.so.cache` file (because `ldconfig` has not been
+  invoked yet).
+
 # Individual compiler flags
 
 Compiler flags end up in the environment variables `CFLAGS`,
@@ -206,6 +348,12 @@ The general (architecture-independent) build flags are:
   it possible to unwind the stack (using C++ `throw` or Rust panics)
   from C callback functions if a C library supports non-local exits
   from them (e.g., via `longjmp`).
+* `-fasynchronous-unwind-tables`: Generate full unwind information
+  covering all program points.  This is required for support of
+  asynchronous cancellation and proper unwinding from signal
+  handlers.  It also makes performance and debugging tools more
+  useful because unwind information is available without having to
+  install (and load) debugging information.
 * `-Wp,-D_GLIBCXX_ASSERTIONS`: Enable lightweight assertions in the
   C++ standard library, such as bounds checking for the subscription
   operator on vectors.  (This flag is added to both `CFLAGS` and
@@ -217,9 +365,22 @@ The general (architecture-independent) build flags are:
   variables.  (If the address of a variable is never taken, it is not
   possible that a buffer overflow is caused by incorrect pointer
   arithmetic involving a pointer to that variable.)
+* `-fstack-clash-protection`: Turn on instrumentation to avoid
+  skipping the guard page in large stack frames.  (Without this flag,
+  vulnerabilities can result where the stack overlaps with the heap,
+  or thread stacks spill into other regions of memory.)  This flag is
+  fully ABI-compatible and has adds very little run-time overhead.
+  This flag is currently not available on aarch64 with the `clang` toolchain.
+* `-flto=auto`: Enable link-time optimization (LTO), using `make` job server
+  integration for parallel processing.  (`gcc` toolchain only)
+* `-ffat-lto-objects`: Generate EFL object files which contain both
+  object code and LTO intermediate representation.  (`gcc` toolchain only)
+* `-flto`: Enable link-time optimization. (`clang` toolchain only)
 * `-grecord-gcc-switches`: Include select GCC command line switches in
   the DWARF debugging information.  This is useful for detecting the
   presence of certain build flags and general hardening coverage.
+* `-fcommon`: This optional flag is used to build legacy software
+  which relies on C tentative definitions.  It is disabled by default.
 
 For hardened builds (which are enabled by default, see above for how
 to disable them), the flag
@@ -247,49 +408,25 @@ command line.  It adds the following flag to the command line:
 To support [binary watermarks for ELF
 objects](https://fedoraproject.org/wiki/Toolchain/Watermark) using
 annobin, the `-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1` flag is
-added by default.  This can be switched off by undefining the
+added by default (with the `gcc` toolchain).  This can be switched off
-`%_annotated_build` RPM macro (see above).
+by undefining the `%_annotated_build` RPM macro (see above).  Binary
+watermarks are currently disabled with the `clang` toolchain.
 
 ### Architecture-specific compiler flags
 
 These compiler flags are enabled for all builds (hardened/annotated or
 not), but their selection depends on the architecture:
 
-*   `-fstack-clash-protection`: Turn on instrumentation to avoid
-    skipping the guard page in large stack frames.  (Without this flag,
-    vulnerabilities can result where the stack overlaps with the heap,
-    or thread stacks spill into other regions of memory.)  This flag is
-    fully ABI-compatible and has adds very little run-time overhead, but
-    is only available on certain architectures (currently aarch64, i386,
-    ppc64, ppc64le, s390x, x86_64).
 *   `-fcf-protection`: Instrument binaries to guard against
     ROP/JOP attacks.  Used on i686 and x86_64.
 *   `-m64` and `-m32`: Some GCC builds support both 32-bit and 64-bit in
     the same compilation.  For such architectures, the RPM build process
     explicitly selects the architecture variant by passing this compiler
     flag.
-*   `-fasynchronous-unwind-tables`: Generate full unwind information
-    covering all program points.  This is required for support of
-    asynchronous cancellation and proper unwinding from signal
-    handlers.  It also makes performance and debugging tools more
-    useful because unwind information is available without having to
-    install (and load) debugging ienformation.
-    Asynchronous unwind tables are enabled for aarch64, i686, ppc64,
-    ppc64le, s390x, and x86_64.  They are not needed on armhfp due to
-    architectural differences in stack management.  On these
-    architectures, `-fexceptions` (see above) still enables regular
-    unwind tables (or they are enabled by default even without this
-    option).
 
 In addition, `redhat-rpm-config` re-selects the built-in default
 tuning in the `gcc` package.  These settings are:
 
-*   **armhfp**: `-march=armv7-a -mfpu=vfpv3-d16  -mfloat-abi=hard`
-    selects an Arm subarchitecture based on the ARMv7-A architecture
-    with 16 64-bit floating point registers.  `-mtune=cortex-8a` selects
-    tuning for the Cortex-A8 implementation (while preserving compatibility
-    with other ARMv7-A implementations).  `-mabi=aapcs-linux` switches to
-    the AAPCS ABI for GNU/Linux.
 *   **i686**: `-march=i686` is used to select a minmum support CPU level
     of i686 (corresponding to the Pentium Pro).  SSE2 support is
     enabled with `-msse2` (so only CPUs with SSE2 support can run the
@@ -301,15 +438,16 @@ tuning in the `gcc` package.  These settings are:
     point math to avoid excess precision issues.  `-mstackrealign`
     avoids relying on the stack alignment guaranteed by the current
     version of the i386 ABI.
-*   **ppc64le**: `-mcpu=power8 -mtune=power8` selects a minimum supported
+*   **ppc64le**: `-mcpu=power9 -mtune=power9` selects a minimum supported
-    CPU level of POWER8 (the first CPU with ppc64le support) and tunes
+    CPU level of POWER9.
-    for POWER8.
+*   **s390x**: `-march=z14 -mtune=z15` specifies a minimum supported CPU
-*   **s390x**: `-march=zEC12 -mtune=z13` specifies a minimum supported CPU
+    level of z14, while optimizing for a subsequent CPU generation
-    level of zEC12, while optimizing for a subsequent CPU generation
+    (z15).
-    (z13).
+*   **x86_64**: `-march=x86-64-v2 -mtune=generic` builds for the
-*   **x86_64**: `-mtune=generic` selects tuning which is expected to
+    [x86-64-v2 micro-architecture level](https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/low-level-sys-info.tex)
-     beneficial for a broad range of current CPUs.
+    and selects tuning which is expected to beneficial for a broad range
-*   **ppc64** and **aarch64** do not have any architecture-specific tuning.
+    of current CPUs.
+*   **aarch64** does not have any architecture-specific tuning.
 
 # Individual linker flags
 
@@ -325,6 +463,10 @@ to the compiler driver `gcc`, and not directly to the link editor
   dynamic linker is instructed to revoke write permissions after
   dynamic linking.  Full protection of relocation data requires the
   `-z now` flag (see below).
+* `--as-needed`: In the final link, only generate ELF dependencies
+  for shared objects that actually provide symbols required by the link.
+  Shared objects which are not needed to fulfill symbol dependencies
+  are essentially ignored due to this flag.
 * `-z defs`: Refuse to link shared objects (DSOs) with undefined symbols
   (optional, see above).
 

SOURCES/macros

@@ -37,29 +37,6 @@
 %__cpp_clang clang-cpp
 
 # Default to the GCC toolchain
-#
-# It is enough to override `toolchain` macro and all relevant macro for C/C++
-# compilers will be switched. Either in the spec or in the command-line.
-#
-#     %global toolchain clang
-#
-# or:
-#
-#     rpmbuild -D "toolchain clang" …
-#
-# Inside a spec file it is also possible to determine which toolchain is in use
-# by testing the same macro. For example:
-#
-#     %if "%{toolchain}" == "gcc"
-#     BuildRequires: gcc
-#     %endif
-#
-# or:
-#
-#     %if "%{toolchain}" == "clang"
-#     BuildRequires: clang compiler-rt
-#     %endif
-#
 %toolchain gcc
 
 %__cc %{expand:%%{__cc_%{toolchain}}}

SOURCES/macros.vpath

@@ -4,4 +4,4 @@
 %_vpath_srcdir .
 
 # directory (doesn't need to exist) where all generated build files will be placed
-%_vpath_builddir %_target_platform
+%_vpath_builddir %{_vendor}-%{_target_os}-build

SPECS/redhat-rpm-config.spec

@@ -6,7 +6,7 @@
 
 Summary: Red Hat specific rpm configuration files
 Name: redhat-rpm-config
-Version: 188
+Version: 190
 Release: 1%{?dist}
 # No version specified.
 License: GPL+
@@ -189,6 +189,13 @@ install -p -m 644 -t %{buildroot}%{_rpmluadir}/fedora/srpm forge.lua
 %doc buildflags.md
 
 %changelog
+* Thu Dec 02 2021 Neal Gompa <ngompa@centosproject.org> - 190-1
+- Make vpath builddir not include arch-specific info
+  Resolves: rhbz#1984679
+
+* Tue Nov 16 2021 Florian Weimer <fweimer@redhat.com> - 189-1
+- buildflags.md: Documentation updates (#2005080)
+
 * Tue Aug 24 2021 Florian Weimer <fweimer@redhat.com> - 188-1
 - redhat-rpm-config: Enable x86-64-v2 baseline for Clang/LLVM (#1890170)