nixpkgs/pkgs/build-support/cc-wrapper/add-flags.sh
Sergei Trofimovich 649ebfbed6 cc-wrapper: change cflags order from cc/crt1/libc to crt1/libc/cc
In https://github.com/NixOS/nixpkgs/issues/158042 I noticed order
mismatch as a bootstrap build failure when building x86_64-linux
against glibc-2.35 in nixpkgs (bootstrap libs has glibc-2.27):

    expand-response-params> ld: /nix/store/p4s4jf7aq6v6z9iazll1aiqwb34aqxq9-bootstrap-tools/lib/crt1.o: in function `_start':
    expand-response-params> /build/glibc-2.27/csu/../sysdeps/x86_64/start.S:101: undefined reference to `__libc_csu_fini'
    expand-response-params> ld: /build/glibc-2.27/csu/../sysdeps/x86_64/start.S:102: undefined reference to `__libc_csu_init'
    expand-response-params> collect2: error: ld returned 1 exit status

Here crt1.o from glibc-2.27 links against libc.so.6 from glibc-2.35.

This happens because ordering of `-L` (influences `libc.so` lookup) and
`-B` (influences `crt1.o` lookup) flags differs:

    expand-response-params>   -B/...-bootstrap-tools/lib
    expand-response-params>   -B/...-glibc-2.35/lib/
    ...
    expand-response-params>   -L/...-glibc-2.35/lib
    expand-response-params>   -L/...-bootstrap-tools/lib

The change makes consistent ordering of `-L`/`-B` and allows getting to
stage4 for `glibc-2.35` target.
2022-02-20 10:45:45 +00:00

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# N.B. It may be a surprise that the derivation-specific variables are exported,
# since this is just sourced by the wrapped binaries---the end consumers. This
# is because one wrapper binary may invoke another (e.g. cc invoking ld). In
# that case, it is cheaper/better to not repeat this step and let the forked
# wrapped binary just inherit the work of the forker's wrapper script.
var_templates_list=(
NIX_CFLAGS_COMPILE
NIX_CFLAGS_COMPILE_BEFORE
NIX_CFLAGS_LINK
NIX_CXXSTDLIB_COMPILE
NIX_CXXSTDLIB_LINK
NIX_GNATFLAGS_COMPILE
)
var_templates_bool=(
NIX_ENFORCE_NO_NATIVE
)
accumulateRoles
# We need to mangle names for hygiene, but also take parameters/overrides
# from the environment.
for var in "${var_templates_list[@]}"; do
mangleVarList "$var" ${role_suffixes[@]+"${role_suffixes[@]}"}
done
for var in "${var_templates_bool[@]}"; do
mangleVarBool "$var" ${role_suffixes[@]+"${role_suffixes[@]}"}
done
# `-B@out@/bin' forces cc to use ld-wrapper.sh when calling ld.
NIX_CFLAGS_COMPILE_@suffixSalt@="-B@out@/bin/ $NIX_CFLAGS_COMPILE_@suffixSalt@"
# Export and assign separately in order that a failing $(..) will fail
# the script.
# Currently bootstrap-tools does not split glibc, and gcc files into
# separate directories. As a workaround we want resulting cflags to be
# ordered as: crt1-cflags libc-cflags cc-cflags. Otherwise we mix crt/libc.so
# from different libc as seen in
# https://github.com/NixOS/nixpkgs/issues/158042
#
# Note that below has reverse ordering as we prepend flags one-by-one.
# Once bootstrap-tools is split into different directories we can stop
# relying on flag ordering below.
if [ -e @out@/nix-support/cc-cflags ]; then
NIX_CFLAGS_COMPILE_@suffixSalt@="$(< @out@/nix-support/cc-cflags) $NIX_CFLAGS_COMPILE_@suffixSalt@"
fi
if [[ "$cInclude" = 1 ]] && [ -e @out@/nix-support/libc-cflags ]; then
NIX_CFLAGS_COMPILE_@suffixSalt@="$(< @out@/nix-support/libc-cflags) $NIX_CFLAGS_COMPILE_@suffixSalt@"
fi
if [ -e @out@/nix-support/libc-crt1-cflags ]; then
NIX_CFLAGS_COMPILE_@suffixSalt@="$(< @out@/nix-support/libc-crt1-cflags) $NIX_CFLAGS_COMPILE_@suffixSalt@"
fi
if [ -e @out@/nix-support/libcxx-cxxflags ]; then
NIX_CXXSTDLIB_COMPILE_@suffixSalt@+=" $(< @out@/nix-support/libcxx-cxxflags)"
fi
if [ -e @out@/nix-support/libcxx-ldflags ]; then
NIX_CXXSTDLIB_LINK_@suffixSalt@+=" $(< @out@/nix-support/libcxx-ldflags)"
fi
if [ -e @out@/nix-support/gnat-cflags ]; then
NIX_GNATFLAGS_COMPILE_@suffixSalt@="$(< @out@/nix-support/gnat-cflags) $NIX_GNATFLAGS_COMPILE_@suffixSalt@"
fi
if [ -e @out@/nix-support/cc-ldflags ]; then
NIX_LDFLAGS_@suffixSalt@+=" $(< @out@/nix-support/cc-ldflags)"
fi
if [ -e @out@/nix-support/cc-cflags-before ]; then
NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@="$(< @out@/nix-support/cc-cflags-before) $NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@"
fi
# Only add darwin min version flag if a default darwin min version is set,
# which is a signal that we're targetting darwin.
if [ "@darwinMinVersion@" ]; then
mangleVarSingle @darwinMinVersionVariable@ ${role_suffixes[@]+"${role_suffixes[@]}"}
NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@="-m@darwinPlatformForCC@-version-min=${@darwinMinVersionVariable@_@suffixSalt@:-@darwinMinVersion@} $NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@"
fi
# That way forked processes will not extend these environment variables again.
export NIX_CC_WRAPPER_FLAGS_SET_@suffixSalt@=1