Merge pull request #225661 from SomeoneSerge/jax-libstdcxx

python3Packages.jax: fix libstdc++ mismatch when built with CUDA

pkgs/development/compilers/cudatoolkit/extension.nix

···
   # E.g. for cudaPackages_11_8 we use gcc11 with gcc12's libstdc++
   # Cf. https://github.com/NixOS/nixpkgs/pull/218265 for context
   backendStdenv = final.callPackage ./stdenv.nix {
-    nixpkgsStdenv = prev.pkgs.stdenv;
-    nvccCompatibleStdenv = prev.pkgs.buildPackages."${finalVersion.gcc}Stdenv";
+    # We use buildPackages (= pkgsBuildHost) because we look for a gcc that
+    # runs on our build platform, and that produces executables for the host
+    # platform (= platform on which we deploy and run the downstream packages).
+    # The target platform of buildPackages.gcc is our host platform, so its
+    # .lib output should be the libstdc++ we want to be writing in the runpaths
+    # Cf. https://github.com/NixOS/nixpkgs/pull/225661#discussion_r1164564576
+    nixpkgsCompatibleLibstdcxx = final.pkgs.buildPackages.gcc.cc.lib;
+    nvccCompatibleCC = final.pkgs.buildPackages."${finalVersion.gcc}".cc;
   };
 
   ### Add classic cudatoolkit package

pkgs/development/compilers/cudatoolkit/stdenv.nix

···
-{ nixpkgsStdenv
-, nvccCompatibleStdenv
+{ lib
+, nixpkgsCompatibleLibstdcxx
+, nvccCompatibleCC
 , overrideCC
+, stdenv
 , wrapCCWith
 }:
 
-overrideCC nixpkgsStdenv (wrapCCWith {
-  cc = nvccCompatibleStdenv.cc.cc;
+let
+  cc = wrapCCWith
+    {
+      cc = nvccCompatibleCC;
 
-  # This option is for clang's libcxx, but we (ab)use it for gcc's libstdc++.
-  # Note that libstdc++ maintains forward-compatibility: if we load a newer
-  # libstdc++ into the process, we can still use libraries built against an
-  # older libstdc++. This, in practice, means that we should use libstdc++ from
-  # the same stdenv that the rest of nixpkgs uses.
-  # We currently do not try to support anything other than gcc and linux.
-  libcxx = nixpkgsStdenv.cc.cc.lib;
-})
+      # This option is for clang's libcxx, but we (ab)use it for gcc's libstdc++.
+      # Note that libstdc++ maintains forward-compatibility: if we load a newer
+      # libstdc++ into the process, we can still use libraries built against an
+      # older libstdc++. This, in practice, means that we should use libstdc++ from
+      # the same stdenv that the rest of nixpkgs uses.
+      # We currently do not try to support anything other than gcc and linux.
+      libcxx = nixpkgsCompatibleLibstdcxx;
+    };
+  cudaStdenv = overrideCC stdenv cc;
+  passthruExtra = {
+    inherit nixpkgsCompatibleLibstdcxx;
+    # cc already exposed
+  };
+  assertCondition = true;
+in
+lib.extendDerivation
+  assertCondition
+  passthruExtra
+  cudaStdenv
+

pkgs/development/python-modules/jaxlib/default.nix

···
 }:
 
 let
-  inherit (cudaPackages) cudatoolkit cudaFlags cudnn nccl;
+  inherit (cudaPackages) backendStdenv cudatoolkit cudaFlags cudnn nccl;
 
   pname = "jaxlib";
   version = "0.3.22";
···
   cudatoolkit_cc_joined = symlinkJoin {
     name = "${cudatoolkit.cc.name}-merged";
     paths = [
-      cudatoolkit.cc
+      backendStdenv.cc
       binutils.bintools # for ar, dwp, nm, objcopy, objdump, strip
     ];
   };
···
           sed -i 's@include/pybind11@pybind11@g' $src
         done
       '' + lib.optionalString cudaSupport ''
+        export NIX_LDFLAGS+=" -L${backendStdenv.nixpkgsCompatibleLibstdcxx}/lib"
         patchShebangs ../output/external/org_tensorflow/third_party/gpus/crosstool/clang/bin/crosstool_wrapper_driver_is_not_gcc.tpl
       '' + lib.optionalString stdenv.isDarwin ''
         # Framework search paths aren't added by bintools hook