cc-wrapper: keep machine cflags if the same target is passed#391944
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alyssais merged 2 commits intoNixOS:stagingfrom Mar 28, 2025
Merged
cc-wrapper: keep machine cflags if the same target is passed#391944alyssais merged 2 commits intoNixOS:stagingfrom
alyssais merged 2 commits intoNixOS:stagingfrom
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Sounds sensible. Could you split |
in preparation for next commit
12b0e8a/6f756b4 work around clang errors when a nix-wrapped compiler is used like a multi-target compiler. it does so by dropping the machineFlags whenever -target/--target is found in the arguments. however this breaks compiler-rt, which is designed to acommodate multi-target builds and always passes `--target`. in its packaging we make sure to only build it for the target we need, essentially disabling the multi-target aspect, but because it still passes --target, the machineFlags are dropped and compiler-rt could end up being for an invalid ABI, producing an unusable stdenv.cc. we could manually pass machineFlags to compiler-rt's cmake build, but IMO it makes more sense to tolerate --target arguments whose value coincides with the wrapper's, keeping the machineFlags in this case.
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done |
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Since #291901 / #317273, compiler-rt doesn't honor machine cflags. This can yield unusable LLVM stdenvs, for example this one even fails to build:
nix-build \ --arg crossSystem '{ config = "riscv32-unknown-linux-gnu"; gcc.arch = "rv32ima"; useLLVM = true; }' \ -A stdenvThis is because compiler-rt always passes
--target, causing machine flags to be dropped.Reading comments from @alyssais, @emilazy and #379593, I think there is general agreement that it's okay for things like compiler-rt to expect a multi-target compiler and pass
--target. #379593 dropped the warning when a--targetmatching the wrapper's is passed. I believe the most natural behavior is for the machine flags to be kept in that case, too, so thatproduce the same binaries. WDYT?
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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.