llvmPackages.libcxx: Fix FreeBSD build

[Ericson2314]

Description of changes

ce789e7 wasn't quite right, because multiple outputs.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[ghost]

ce789e7 wasn't quite right, because multiple outputs.

ce789e7 got it right except for llvm12, all the others (13-git) were handled properly. not sure how llvm12 was missed as i diffed the files against themselves but i might've been sloppy there if the freebsd build was broken in other ways, though i thought 12 worked and 13 & 14 were broken due to libunwind or something, but that could've been pkgsLLVM or aarch64 pkgsLLVM.

nixpkgs/pkgs/development/compilers/llvm/16/libcxx/default.nix

Lines 101 to 107 in ce789e7

	# libc++.so is a linker script which expands to multiple libraries,
	# libc++.so.1 and libc++abi.so or the external cxxabi. ld-wrapper doesn't
	# support linker scripts so the external cxxabi needs to be symlinked in
	postInstall = lib.optionalString (cxxabi != null) ''
	lndir ${lib.getDev cxxabi}/include ''${!outputDev}/include/c++/v1
	lndir ${lib.getLib cxxabi}/lib ''${!outputLib}/lib
	'';

[Ericson2314]

@ghostofannalee these sorts of mistakes are quite likely --- I don't begrudge the author. That is why @RossComputerGuy doing the deduplication is such a good thing! --- it's best to make that mistake much less likely than try to just be more vigilant than is feasible.

[ghost]

@ghostofannalee these sorts of mistakes are quite likely --- I don't begrudge the author. That is why @RossComputerGuy doing the deduplication is such a good thing! --- it's best to make that mistake much less likely than try to just be more vigilant than is feasible.

hmm, i think for llvm12 it might have needed to be $out as when i try to build nix-build -A pkgsCross.x86_64-freebsd.libcxx it fails with:

/nix/store/fv8plrk4s537n2hrnr2djhf734b3lkx8-libcxx-x86_64-unknown-freebsd13-12.0.1-dev/include/c++/v1: No such file or directory

pkgsCross.x86_64-freebsd.llvmPackages_16.libcxx works (with $dev) tho, so i think ce789e7 was correct in using $out for llvm12 and $dev for the rest.

[RossComputerGuy]

@ghostofannalee That just sounds like the path that the directory being moved to doesn't exist.

[Ericson2314]

@ghostofannalee Even if libc++ 12 puts it in $out, Nix will move it to $dev in the fixup stage. So I think we can just fix this by moving it to $dev earlier.

[ghost]

@ghostofannalee Even if libc++ 12 puts it in $out, Nix will move it to $dev in the fixup stage. So I think we can just fix this by moving it to $dev earlier.

that worked for llvm12 and llvm16

diff --git a/pkgs/development/compilers/llvm/common/libcxx/default.nix b/pkgs/development/compilers/llvm/common/libcxx/default.nix
index 0e91f50551c5..c630213797db 100644
--- a/pkgs/development/compilers/llvm/common/libcxx/default.nix
+++ b/pkgs/development/compilers/llvm/common/libcxx/default.nix
@@ -124,6 +125,7 @@ stdenv.mkDerivation (rec {
   # libc++.so.1 and libc++abi.so or the external cxxabi. ld-wrapper doesn't
   # support linker scripts so the external cxxabi needs to be symlinked in
   postInstall = lib.optionalString (cxxabi != null) ''
+    [[ -d $out/include ]] && { mkdir -p $dev; mv $out/include $dev; }
     lndir ${lib.getDev cxxabi}/include $dev/include/c++/v1
     lndir ${lib.getLib cxxabi}/lib $out/lib
   '';

[edit] added diff in PR #306027