nixpkgs/pkgs/stdenv/cross/default.nix

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{ lib
, localSystem, crossSystem, config, overlays, crossOverlays ? []
}:
let
bootStages = import ../. {
inherit lib localSystem overlays;
crossSystem = localSystem;
crossOverlays = [];
# Ignore custom stdenvs when cross compiling for compatability
config = builtins.removeAttrs config [ "replaceStdenv" ];
};
in lib.init bootStages ++ [
# Regular native packages
(somePrevStage: lib.last bootStages somePrevStage // {
# It's OK to change the built-time dependencies
allowCustomOverrides = true;
})
# Build tool Packages
(vanillaPackages: {
inherit config overlays;
selfBuild = false;
stdenv =
assert vanillaPackages.stdenv.buildPlatform == localSystem;
assert vanillaPackages.stdenv.hostPlatform == localSystem;
assert vanillaPackages.stdenv.targetPlatform == localSystem;
vanillaPackages.stdenv.override { targetPlatform = crossSystem; };
# It's OK to change the built-time dependencies
allowCustomOverrides = true;
})
top-level: Introduce `buildPackages` for resolving build-time deps [N.B., this package also applies to the commits that follow it in the same PR.] In most cases, buildPackages = pkgs so things work just as before. For cross compiling, however, buildPackages is resolved as the previous bootstrapping stage. This allows us to avoid the mkDerivation hacks cross compiling currently uses today. To avoid a massive refactor, callPackage will splice together both package sets. Again to avoid churn, it uses the old `nativeDrv` vs `crossDrv` to do so. So now, whether cross compiling or not, packages with get a `nativeDrv` and `crossDrv`---in the non-cross-compiling case they are simply the same derivation. This is good because it reduces the divergence between the cross and non-cross dataflow. See `pkgs/top-level/splice.nix` for a comment along the lines of the preceding paragraph, and the code that does this splicing. Also, `forceNativeDrv` is replaced with `forceNativePackages`. The latter resolves `pkgs` unless the host platform is different from the build platform, in which case it resolves to `buildPackages`. Note that the target platform is not important here---it will not prevent `forcedNativePackages` from resolving to `pkgs`. -------- Temporarily, we make preserve some dubious decisions in the name of preserving hashes: Most importantly, we don't distinguish between "host" and "target" in the autoconf sense. This leads to the proliferation of *Cross derivations currently used. What we ought to is resolve native deps of the cross "build packages" (build = host != target) package set against the "vanilla packages" (build = host = target) package set. Instead, "build packages" uses itself, with (informally) target != build in all cases. This is wrong because it violates the "sliding window" principle of bootstrapping stages that shifting the platform triple of one stage to the left coincides with the next stage's platform triple. Only because we don't explicitly distinguish between "host" and "target" does it appear that the "sliding window" principle is preserved--indeed it is over the reductionary "platform double" of just "build" and "host/target". Additionally, we build libc, libgcc, etc in the same stage as the compilers themselves, which is wrong because they are used at runtime, not build time. Fixing this is somewhat subtle, and the solution and problem will be better explained in the commit that does fix it. Commits after this will solve both these issues, at the expense of breaking cross hashes. Native hashes won't be broken, thankfully. -------- Did the temporary ugliness pan out? Of the packages that currently build in `release-cross.nix`, the only ones that have their hash changed are `*.gcc.crossDrv` and `bootstrapTools.*.coreutilsMinimal`. In both cases I think it doesn't matter. 1. GCC when doing a `build = host = target = foreign` build (maximally cross), still defines environment variables like `CPATH`[1] with packages. This seems assuredly wrong because whether gcc dynamically links those, or the programs built by gcc dynamically link those---I have no idea which case is reality---they should be foreign. Therefore, in all likelihood, I just made the gcc less broken. 2. Coreutils (ab)used the old cross-compiling infrastructure to depend on a native version of itself. When coreutils was overwritten to be built with fewer features, the native version it used would also be overwritten because the binding was tight. Now it uses the much looser `BuildPackages.coreutils` which is just fine as a richer build dep doesn't cause any problems and avoids a rebuild. So, in conclusion I'd say the conservatism payed off. Onward to actually raking the muck in the next PR! [1]: https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html
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# Run Packages
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(buildPackages: let
adaptStdenv =
if crossSystem.isStatic
then buildPackages.stdenvAdapters.makeStatic
else lib.id;
in {
inherit config;
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overlays = overlays ++ crossOverlays;
top-level: Introduce `buildPackages` for resolving build-time deps [N.B., this package also applies to the commits that follow it in the same PR.] In most cases, buildPackages = pkgs so things work just as before. For cross compiling, however, buildPackages is resolved as the previous bootstrapping stage. This allows us to avoid the mkDerivation hacks cross compiling currently uses today. To avoid a massive refactor, callPackage will splice together both package sets. Again to avoid churn, it uses the old `nativeDrv` vs `crossDrv` to do so. So now, whether cross compiling or not, packages with get a `nativeDrv` and `crossDrv`---in the non-cross-compiling case they are simply the same derivation. This is good because it reduces the divergence between the cross and non-cross dataflow. See `pkgs/top-level/splice.nix` for a comment along the lines of the preceding paragraph, and the code that does this splicing. Also, `forceNativeDrv` is replaced with `forceNativePackages`. The latter resolves `pkgs` unless the host platform is different from the build platform, in which case it resolves to `buildPackages`. Note that the target platform is not important here---it will not prevent `forcedNativePackages` from resolving to `pkgs`. -------- Temporarily, we make preserve some dubious decisions in the name of preserving hashes: Most importantly, we don't distinguish between "host" and "target" in the autoconf sense. This leads to the proliferation of *Cross derivations currently used. What we ought to is resolve native deps of the cross "build packages" (build = host != target) package set against the "vanilla packages" (build = host = target) package set. Instead, "build packages" uses itself, with (informally) target != build in all cases. This is wrong because it violates the "sliding window" principle of bootstrapping stages that shifting the platform triple of one stage to the left coincides with the next stage's platform triple. Only because we don't explicitly distinguish between "host" and "target" does it appear that the "sliding window" principle is preserved--indeed it is over the reductionary "platform double" of just "build" and "host/target". Additionally, we build libc, libgcc, etc in the same stage as the compilers themselves, which is wrong because they are used at runtime, not build time. Fixing this is somewhat subtle, and the solution and problem will be better explained in the commit that does fix it. Commits after this will solve both these issues, at the expense of breaking cross hashes. Native hashes won't be broken, thankfully. -------- Did the temporary ugliness pan out? Of the packages that currently build in `release-cross.nix`, the only ones that have their hash changed are `*.gcc.crossDrv` and `bootstrapTools.*.coreutilsMinimal`. In both cases I think it doesn't matter. 1. GCC when doing a `build = host = target = foreign` build (maximally cross), still defines environment variables like `CPATH`[1] with packages. This seems assuredly wrong because whether gcc dynamically links those, or the programs built by gcc dynamically link those---I have no idea which case is reality---they should be foreign. Therefore, in all likelihood, I just made the gcc less broken. 2. Coreutils (ab)used the old cross-compiling infrastructure to depend on a native version of itself. When coreutils was overwritten to be built with fewer features, the native version it used would also be overwritten because the binding was tight. Now it uses the much looser `BuildPackages.coreutils` which is just fine as a richer build dep doesn't cause any problems and avoids a rebuild. So, in conclusion I'd say the conservatism payed off. Onward to actually raking the muck in the next PR! [1]: https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html
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selfBuild = false;
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stdenv = adaptStdenv (buildPackages.stdenv.override (old: rec {
buildPlatform = localSystem;
hostPlatform = crossSystem;
targetPlatform = crossSystem;
# Prior overrides are surely not valid as packages built with this run on
# a different platform, and so are disabled.
overrides = _: _: {};
extraBuildInputs = [ ] # Old ones run on wrong platform
++ lib.optionals hostPlatform.isDarwin [ buildPackages.targetPackages.darwin.apple_sdk.frameworks.CoreFoundation ]
;
allowedRequisites = null;
hasCC = !targetPlatform.isGhcjs;
cc = if crossSystem.useiOSPrebuilt or false
then buildPackages.darwin.iosSdkPkgs.clang
else if crossSystem.useAndroidPrebuilt or false
then buildPackages."androidndkPkgs_${crossSystem.ndkVer}".clang
else if targetPlatform.isGhcjs
# Need to use `throw` so tryEval for splicing works, ugh. Using
# `null` or skipping the attribute would cause an eval failure
# `tryEval` wouldn't catch, wrecking accessing previous stages
# when there is a C compiler and everything should be fine.
then throw "no C compiler provided for this platform"
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else if crossSystem.isDarwin
then buildPackages.llvmPackages.libcxxClang
else if crossSystem.useLLVM or false
then buildPackages.llvmPackages.clangUseLLVM
else buildPackages.gcc;
extraNativeBuildInputs = old.extraNativeBuildInputs
++ lib.optionals
(hostPlatform.isLinux && !buildPlatform.isLinux)
[ buildPackages.patchelf ]
++ lib.optional
(let f = p: !p.isx86 || builtins.elem p.libc [ "musl" "wasilibc" "relibc" ] || p.isiOS || p.isGenode;
in f hostPlatform && !(f buildPlatform) )
buildPackages.updateAutotoolsGnuConfigScriptsHook
# without proper `file` command, libtool sometimes fails
# to recognize 64-bit DLLs
++ lib.optional (hostPlatform.config == "x86_64-w64-mingw32") buildPackages.file
;
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}));
})
]