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cudaPackages.cuda_nvcc: wrap binary so NVCC can always find compiler #465329

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Merged
SomeoneSerge merged 1 commit into from
Nov 28, 2025
Merged

cudaPackages.cuda_nvcc: wrap binary so NVCC can always find compiler #465329

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17 changes: 14 additions & 3 deletions pkgs/development/cuda-modules/packages/cuda_nvcc.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
cuda_cccl,
lib,
libnvvm,
makeBinaryWrapper,
}:
buildRedist (finalAttrs: {
redistName = "cuda";
Expand All @@ -22,6 +23,10 @@ buildRedist (finalAttrs: {
# The nvcc and cicc binaries contain hard-coded references to /usr
allowFHSReferences = true;

nativeBuildInputs = [
makeBinaryWrapper
];

# Entries here will be in nativeBuildInputs when cuda_nvcc is in nativeBuildInputs
propagatedBuildInputs = [ setupCudaHook ];

Expand Down Expand Up @@ -144,13 +149,19 @@ buildRedist (finalAttrs: {
EOF
''
# Add the dependency on backendStdenv.cc to the nvcc.profile.
# NOTE: NVCC explodes in horrifying fashion if GCC is not on PATH -- it fails even before
# reading nvcc.profile!
+ ''
nixLog "adding backendStdenv.cc to nvcc.profile"
nixLog "setting compiler-bindir to backendStdenv.cc in nvcc.profile"
cat << EOF >> "''${!outputBin:?}/bin/nvcc.profile"

# Fix a compatible backend compiler
PATH += "${backendStdenv.cc}/bin":
compiler-bindir = ${backendStdenv.cc}/bin
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@SomeoneSerge SomeoneSerge Nov 26, 2025

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Ah damn this is off by 1 again: nvcc here is hostTarget, and cc - buildHost

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@SomeoneSerge SomeoneSerge Nov 26, 2025

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OTOH, we never made cross actually work, might as well postpone the larping

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@ConnorBaker ConnorBaker Nov 26, 2025

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cc is unspliced but backendStdenv is spliced and from pkgsHostTarget (the default package set drawn from by callPackage) so I would hope cc is also from hostTarget.

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@SomeoneSerge SomeoneSerge Nov 28, 2025

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Nooo that's the thing about stdenvs, they're always offset by -1:

$ nix eval -f "<nixpkgs>" --argstr crossSystem aarch64-linux stdenv.cc.name
"aarch64-unknown-linux-gnu-gcc-wrapper-14.3.0"

But maybe we should merge regardless and fix whenever

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Yeah screw it

EOF

nixLog "wrapping nvcc to add backendStdenv.cc to its PATH"
wrapProgramBinary \
"''${!outputBin:?}/bin/nvcc" \
--prefix PATH : ${lib.makeBinPath [ backendStdenv.cc ]}
''
);

Expand Down
3 changes: 0 additions & 3 deletions pkgs/development/cuda-modules/packages/setupCudaHook/package.nix
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Expand Up @@ -5,9 +5,6 @@ makeSetupHook {

substitutions.setupCudaHook = placeholder "out";

# Point NVCC at a compatible compiler
substitutions.ccRoot = "${backendStdenv.cc}";

# Required in addition to ccRoot as otherwise bin/gcc is looked up
# when building CMakeCUDACompilerId.cu
substitutions.ccFullPath = "${backendStdenv.cc}/bin/${backendStdenv.cc.targetPrefix}c++";
Expand Down
2 changes: 0 additions & 2 deletions pkgs/development/cuda-modules/packages/setupCudaHook/setup-cuda-hook.sh
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Expand Up @@ -92,8 +92,6 @@ setupCUDAToolkitCompilers() {
export CUDAHOSTCXX="@ccFullPath@"
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@SomeoneSerge SomeoneSerge Nov 26, 2025

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Probably want to break up the hook's dependency on the cc too 🤔 Because now we have 3 references all from different places

fi

appendToVar NVCC_PREPEND_FLAGS "--compiler-bindir=@ccRoot@/bin"

# NOTE: We set -Xfatbin=-compress-all, which reduces the size of the compiled
# binaries. If binaries grow over 2GB, they will fail to link. This is a problem for us, as
# the default set of CUDA capabilities we build can regularly cause this to occur (for
Expand Down
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