core/pkgs/by-name/gc/gcc/common/libgcc-buildstuff.nix

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{ lib, stdenv }:
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# Trick to build a gcc that is capable of emitting shared libraries *without* having the
# targetPlatform libc available beforehand. Taken from:
# https://web.archive.org/web/20170222224855/http://frank.harvard.edu/~coldwell/toolchain/
# https://web.archive.org/web/20170224235700/http://frank.harvard.edu/~coldwell/toolchain/t-linux.diff
let
# crt{i,n}.o are the first and last (respectively) object file
# linked when producing an executable. Traditionally these
# files are delivered as part of the C library, but on GNU
# systems they are in fact built by GCC. Since libgcc needs to
# build before glibc, we can't wait for them to be copied by
# glibc. At this early pre-glibc stage these files sometimes
# have different names.
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crtstuff-ofiles = if stdenv.targetPlatform.isPower then
"ecrti.o ecrtn.o ncrti.o ncrtn.o"
else
"crti.o crtn.o";
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# Normally, `SHLIB_LC` is set to `-lc`, which means that
# `libgcc_s.so` cannot be built until `libc.so` is available.
# The assignment below clobbers this variable, removing the
# `-lc`.
#
# On PowerPC we add `-mnewlib`, which means "libc has not been
# built yet". This causes libgcc's Makefile to use the
# gcc-built `{e,n}crt{n,i}.o` instead of failing to find the
# versions which have been repackaged in libc as `crt{n,i}.o`
#
SHLIB_LC = lib.optionalString stdenv.targetPlatform.isPower "-mnewlib";
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in ''
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echo 'libgcc.a: ${crtstuff-ofiles}' >> libgcc/Makefile.in
echo 'SHLIB_LC=${SHLIB_LC}' >> libgcc/Makefile.in
''
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# Meanwhile, crt{i,n}.S are not present on certain platforms
# (e.g. LoongArch64), resulting in the following error:
#
# No rule to make target '../../../gcc-xx.x.x/libgcc/config/loongarch/crti.S', needed by 'crti.o'. Stop.
#
# For LoongArch64 and S390, a hacky workaround is to simply touch them,
# as the platform forces .init_array support.
#
# https://www.openwall.com/lists/musl/2022/11/09/3
#
# 'parsed.cpu.family' won't be correct for every platform.
+ lib.optionalString (stdenv.targetPlatform.isLoongArch64
|| stdenv.targetPlatform.isS390 || stdenv.targetPlatform.isAlpha) ''
touch libgcc/config/${stdenv.targetPlatform.parsed.cpu.family}/crt{i,n}.S
''