Fix useMoldLinker when cross compiling #400749
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After NixOS#400734 we can make useMoldLinker work when cross compiling. We need the following: - Need to use pkgs.buildPackages.mold so that we use mold binaries for the build machine instead of the host. - Need to create unprefixed ld.mold wrapper because gcc will not look for a triple-prefixed ld.mold when passing -fuse-ld=mold. Tested on an aarch64 machine with this change + NixOS#400734: $ nix-build -K --expr 'with import "${./.}" { crossSystem = { config = "x86_64-unknown-linux-gnu"; }; }; hello.override { stdenv = useMoldLinker stdenv; }' && strings result/bin/hello | grep mold /nix/store/w1yg0am7iyqsgi253h84lsp92178sgfi-hello-x86_64-unknown-linux-gnu-2.12.1 mold 2.37.1 (compatible with GNU ld)
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Apr 24, 2025
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this does require the linked PR to properly fix cross compilation, but it should be safe to merge these in any order.
given the previous failure mode would appear to be that mold was just silently not being used for cross compilation, it would be nice to have some regression test for that if it's not too difficult to write.
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Cherrypicked this onto #400734, got this when running on x86_64-linux. ❯ nix-build -K --expr 'with import "${./.}" { crossSystem = { config = "aarch64-unknown-linux-gnu"; }; }; hello.override { stdenv = useMoldLinker stdenv; }' && strings result/bin/hello | grep mold
/nix/store/vdcwp8jwl9561v5b5hjq537vnsshcdya-hello-aarch64-unknown-linux-gnu-2.12.1
mold 2.37.1 (compatible with GNU ld) |
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After #400734 we can make useMoldLinker work when cross compiling. We need the following:
Tested on an aarch64 machine with this change + #400734:
Things done
nix.conf? (See Nix manual)sandbox = relaxedsandbox = truenix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage./result/bin/)Add a 👍 reaction to pull requests you find important.