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glaucus

gcc

  • Disable bootstrap; stage1 is good enough
  • Use a different libexecdir
  • bootstrap-lto build configuration adjusts CFLAGS and LDFLAGS
  • --with-build-config=bootstrap-lto-lean has to be used with make profiledbootstrap
  • Personal testing showed negligible differences between disable-bootstrap and bootstrap-lean, with notable differences against bootstrap-native (latter is ~5% smaller):
                      bootstrap-native  disable-bootstrap        diff       %
lto-dump                    40,730,072         42,812,208  +2,082,136  +5.11%
g++                          1,094,704          1,098,840      +4,136  +0.38%
gcc                          1,094,704          1,094,744         +40  +0.00%
gcov                           358,904            358,944         +40  +0.01%
gcc-ar                          26,424             30,544      +4,120  +15.59%


cc1plus                     44,880,264         46,822,920  +1,942,656  +4.33%
cc1                         42,226,152         44,263,176  +2,037,024  +4.82%
lto1                        40,730,072         42,812,272  +2,082,200  +5.11%
libgcc.a                     8,233,264          8,253,544     +20,280  +0.25%
lto-wrapper                    866,808            862,744      -4,064  -0.47%
libgcov.a                      378,410            381,562      +3,152  +0.83%
collect2                       313,848            309,784      -4,064  -1.29%
liblto_plugin.so                67,192             75,536      +8,344  +12.42%
g++-mapper-server               55,040             51,112      -3,928  -7.14%


libstdc++.so.6.0.33          2,427,408          2,501,200     +73,792  +3.04%
libgcc_s.so.1                  169,904            826,832    +656,928  +386.65%
libquadmath.so.0.0.0           296,488            296,632        +144  +0.05%
libgomp.so.1.0.0               277,064            277,120         +56  +0.02%
libitm.so.1.0.0                 71,456             79,704      +8,248  +11.54%
libatomic.so.1.2.0              22,056             22,120         +64  +0.29%
  • bootstrap-debug-lean is slower and bigger compared to bootstrap-debug
  • BOOT_CFLAGS, BOOT_LDFLAGS and --with-boot-ldflags only make sense when bootstrapping gcc; applies to stages 2 and 3
  • LD_FOR_TARGET, STAGE1_CFLAGS and STAGE1_LDFLAGS apply to stage 1
  • --enable-link-mutex has been deprecated, use --enable-link-serialization=1 instead: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109310 (=1 is sane, any higher value might thrash the system)
  • cc1 depends on mpc at run time
  • Depends on tar for the make target install-headers-tar
  • As of 14.1, new configure options --enable-host-pie, to build the compiler executables as PIE; and --enable-host-bind-now, to link the compiler executables with -Wl,-z,now to enable additional hardening
  • --enable-host-shared has a performance penalty on gcc
  • Might need a lex/flex library libfl.a:
checking for lex library... not found
configure: WARNING: required lex library not found; giving up on touch lex.yy.c
  • BOOT_CXXFLAGS has been deprecated
  • CFLAGS, CXXFLAGS, CFLAGS_FOR_TARGET and CXXFLAGS_FOR_TARGET are being picked up from the environment; the latter two are automatically assigned to the former two
  • Check clocale to use for libstdc++; generic vs --disable-clocale?
  • libgcc_s.so.1 size dramatically reduced when using stage1 flags (from ~ 830k to ~ 170k)
  • otool is for mach os, and is part of LLVM; the otool not found error is normal for gcc
  • Move cpp from lib to bin?
  • The following (ignored) errors occur when building libstdc++-v3 (in all stages):
libstdc++-v3.log:945:make[1]: [Makefile:1831: x86_64-glaucus-linux-musl/bits/largefile-config.h] Error 1 (ignored)
libstdc++-v3.log:946:make[1]: [Makefile:1832: x86_64-glaucus-linux-musl/bits/largefile-config.h] Error 1 (ignored)

According to tmp/gcc/gcc-14.2.0/build/x86_64-glaucus-linux-musl/libstdc++-v3/include/Makefile:

...
# This header is not installed, it's only used to build libstdc++ itself.
${host_builddir}/largefile-config.h: ${CONFIG_HEADER} stamp-${host_alias}
  @rm -f $@.tmp
  @-grep 'define _DARWIN_USE_64_BIT_INODE' ${CONFIG_HEADER} >> $@.tmp
  @-grep 'define _FILE_OFFSET_BITS' ${CONFIG_HEADER} >> $@.tmp
  @-grep 'define _LARGE_FILES' ${CONFIG_HEADER} >> $@.tmp
  @mv $@.tmp $@
...

and indeed if we check tmp/gcc/gcc-14.2.0/build/x86_64-glaucus-linux-musl/libstdc++-v3/include/x86_64-glaucus-linux-musl/bits/largefile-config.h:

# define _DARWIN_USE_64_BIT_INODE 1

which means that the first @-grep is working, while the latter two are not causing these two Error 1 (ignored) messages; and no this is not related to a race condition and it does not go away neither with -j 1 nor with --disable-largefile

  • No need to fix headers or includes on glaucus
  • libsupc++ is the ABI library and it is a subset of libstdc++
  • Alpine sets libat_cv_have_ifunc=no before gcc configure; related to libatomic, and Alpaquita are providing ifunc and are not setting this variable
  • Alpine uses gcc-go to bootstrap go
  • -fstack-protector-strong is the default; no need to lower ssp-buffer-size from the default 8 to 4, but glaucus still does it
  • Disable libsanitizer for gcc with musl (only ASan works), and prefer clang and compiler-rt for sanitizers
  • Do we need to remove usr/lib/gcc/x86_64-glaucus-linux-musl/$ver/install-tools/ (and include-fixed/)?
  • Patching gcc to link libatomic to everything is not needed on x86_64 (Alpine enables it for riscv64)
  • If you are not building a C library in the same source tree as GCC, you should also provide the target libraries and headers before configuring GCC, specifying the directories with —with-sysroot or —with-headers and —with-libs. Many targets also require “start files” such as crt0.o and crtn.o which are linked into each executable. There may be several alternatives for crt0.o, for use with profiling or other compilation options. Check your target’s definition of STARTFILE_SPEC to find out what start files it uses.
  • No need to perform this maneuver from LFS thanks to our toolchain design:
cat gcc/limitx.h gcc/glimits.h gcc/limity.h > \
  `dirname $($target-gcc -print-libgcc-file-name)`/include/limits.h
  • --enable-gnu-indirect-function (ifunc) is only available for glibc and is enabled by default on glibc systems; it won’t hurt to explicitly disable it on musl
  • libat_cv_have_ifunc=no explicitly disables ifunc for libatomic:
    • creates conflicts on ARM as it -march/-mcpu expect it (Alpine)
    • ifunc attributes detection is broken in configure scripts which makes sense to force disable it for non-glibc systems (it is used extensively by the Go language) (Alpine)
  • For bootstrap builds we hardcode sysroot because it is split from the toolchain and located in its own directory outside of the toolchain directory; this does not change with build-sysroot because build-sysroot controls where gcc finds its libaries, headers and stuff during its build, while sysroot controls where it finds them after the build when building stuff, in a sense this makes the toolchain not so relocatable (well it will still look under sysroot (which is cross in our condition) for stuff regardless of what the toolchain directory is named or located, meaning if we moved glaucus/toolchain over to /tmp/someOtherDir it will still look for stuff under glaucus/cross wherever that is, so that’s a minor win), but it is not meant to be, this is because we want to keep cross (basically our sysroot) separate from the toolchain so we can populate it later on with stage 2 stuff and turn it into a bootable image; this is not mussel after all
  • --with-libstdcxx-lock-policy=atomic uses less memory and is simpler than mutex
  • --enable-linker-build-id is off by default
  • Disable transactional memory (Intel TSX) --disable-tm-clone-registry as it is obsolete nowadays (see -fgnu-tm)
  • -Qn is an old obsolete synonym for -fno-ident
  • -mmusl is the default on *-*-linux-*musl* targets
  • -fomit-frame-pointer is used by default with -Os (and -O2)
  • From ld manual:
Note that the location of the compiler originated plugins is different from the place where the ar, nm and ranlib programs search for their plugins. In order for those commands to make use of a compiler based plugin it must first be copied into the ${libdir}/bfd-plugins directory. All gcc based linker plugins are backward compatible, so it is sufficient to just copy in the newest one.
  • Graphite is no longer being developed/maintained as it used to be
  • Baseline gcc optimizes performs better loop optimizations without graphite (isl, and cloog/ppl previously) than with it
  • Installing the linker plugin into $libdir/bfd-plugins has the same effect as usage of the command wrappers (gcc-ar, gcc-nm and gcc-ranlib)
  • --with-cross-host is deprecated (according to a FIXME comment in configure)
  • Configure libstdc++-v3 with --enable-libstdcxx-time as musl has clock_gettime
  • mudflap removed since 4.9 (musl does not support libmudflag anyways)
  • intel mpx and sfi are unmaintained and were dropped from both the kernel and gcc (musl does not support libmpx anyways as it lacks secure_getenv and struct _libc_fpstate)
  • libcilkrts removed since 2017
  • a custom tuple like x86_64-glaucus-linux-musl is good for cross-compilation otherwise it is bad because it assumes the compiler is failing for many tests; it is better to have x86_64-pc-linux-musl as the final target
  • config.guess and config.sub prefer x86_64-pc to x86_64-unknown (or not specifying anything though for musl it is sufficient)
  • Uses ~2GB of memory per make job
  • test suite takes a lot of time (several hours)
  • LTO is not a default language, but is built by default because --enable-lto is enabled by default
  • --disable-libstdcxx-pch prevents the precompiled headers from being built (which is the default behavior); we don’t use these headers and they take up space
  • --disable-libstdcxx-visibility causes missing symbols from libstdc++ when linking and running programs that depend on it
  • musl-gcc-cross patches from Rich Felker were added to upstream gcc as of 10.2.0+
  • bootstrap-O3 might cause regressions

Not Relocatable

Section titled “Not Relocatable”

Relocatable:

Section titled “Relocatable:”

References

Section titled “References”