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{ lib
, stdenv
}:
# 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.
crtstuff-ofiles =
if stdenv.targetPlatform.isPower
then "ecrti.o ecrtn.o ncrti.o ncrtn.o"
else "crti.o crtn.o";
# 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";
in ''
echo 'libgcc.a: ${crtstuff-ofiles}' >> libgcc/Makefile.in
echo 'SHLIB_LC=${SHLIB_LC}' >> libgcc/Makefile.in
''
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