cross compilation of clang (or llvmPackages*.tools) fails to evaluate

[dtzWill]

Issue description

Evaluation complains that llvmPackages attribute doesn't exist in targetPackages.

Indeed, investigating with nix repl suggests targetPackages only contains stdenv.

Steps to reproduce

• $ nix build -f channel:nixos-unstable pkgsCross.musl64.clang

OR

$ nix build -f channel:nixos-unstable pkgsCross.aarch64-multiplatform.clang

and so on.

FWIW occurs when directly setting crossSystem instead of using convenience pkgsCross.

[dtzWill]

This somehow made it to 18.09 as well? :(

To see it non-broken, you'll have to use 18.03 which is before the nice pkgsCross bits, so something like:

$ nix build -f channel:nixos-18.03 --arg crossSystem '{config="x86_64-unknown-linux-musl";}' clang

[dtzWill]

Not sure what caused it, but I bet @Ericson2314 knows how to fix it 😇

[dtzWill]

• Goes back before 18.09 branch
• clangStdenv and llvm work -- as does llvmPackages{,_N}.{llvm,stdenv,libcxx}
• llvmPackages*.tools does not

Hmm this may be known and possibly mentioned but I forgot...? If nothing else it'd be good to improve this error so it's clearer to new folk or those who forget things ;).

---

git bisect says 6e7e22d is "first bad commit", FWIW.

[Ericson2314]

This is because pkgs.targetPackages != pkgs in cross builds. This because at then end of /pkgs/stdenv/booter.nix it makes a fake stadenv so things like targetPackages.stdenv.cc go to a good choice of C compiler to use at run time (a choice that would technically be made by the next change).

In this case, well, there is no next stage so hard to tell what runtime libraries to use! It's unfortunate. Not sure what the best fix is.

nix build -f channel:nixos-unstable pkgsCross.musl64.llvmPackages.clang-unwrapped

is fine since it has no runtime libs and indeed evals fine.

[Ericson2314]

So yes, the real solution is issue #49481 / #26004 haha

[dtzWill]

On Tue, 30 Oct 2018 15:00:23 -0700, John Ericson ***@***.***> wrote: This is because `targetPackages.targetPackages` = `targetPackages` in cross builds. This because at then end of `/pkgs/stdenv/booter.nix` it makes a fake stadenv so things like `targetPackages.stdenv.cc` go to a good choice of C compiler to use at run time (a choice that would technically be made by the next change). In this case, well, there is no next stage so hard to tell what runtime libraries to use! It's unfortunate. Not sure what the best fix is.

Shouldn't this default to `hostPackages` or so -- we seem able to populate `targetPackages` under normal circumstances, this seems similar? That said, once I realized/discovered this only errors with `clang` and `llvmPackages.tools` this is less of a problem in practice. I think.

…

``` nix build -f channel:nixos-unstable pkgsCross.musl64.llvmPackages.clang-unwrapped ``` builds fine since it has no runtime libs. -- You are receiving this because you authored the thread. Reply to this email directly or view it on GitHub: #49475 (comment) part: text/html

[Ericson2314]

@dtzWill Yeah maybe we should change it so targetPackages = pkgs // { stdenv = fake }; in pkgs/stdenv/booter.nix instead.

[matthewbauer]

This looks to be fixed?