Commit 90474914 authored by Sergei Trofimovich's avatar Sergei Trofimovich
Browse files

gcc: do not allow version skew when cross-building gcc 

When `gcc` is cross-built (`build` != `target` && `host` == `target`)
`gcc` assumes that it has a compatible cross-compiler in the environment
that can build target libraries. Version of a cross-compiler has to
match the compiler being cross-built as libraries frequently use fresh
compiler features, like `-std=c++26` or target-specific types like
`_Bfloat16`.

Version mismatch causes build failures like:

    https://github.com/NixOS/nixpkgs/issues/351905

Similar problems (but on a smaller scale) happen when a `gcc`
cross-compiler is built (`build` == `host` && `host` != `target`) built
by a mismatching version of a native compiler (`build` == `host` &&
`host` == `target`). That was worked around by forcing `gcc9Stdenv` for
older compiler versions.

Let's fix both problems by requiring the same compiler version for
cross-case.

Closes: https://github.com/NixOS/nixpkgs/issues/351905
parent 98850724

pkgs/development/compilers/gcc/all.nix

+21 −3
Original line number Diff line number Diff line 
{ lib

, stdenv

, gccStdenv

, gcc9Stdenv

, pkgs

, callPackage

, isl_0_20

, libcCross
@@ -15,6 +14,7 @@ let 
  versions = import ./versions.nix;

  gccForMajorMinorVersion = majorMinorVersion:

    let

      majorVersion = lib.versions.major majorMinorVersion;

      atLeast = lib.versionAtLeast majorMinorVersion;

      attrName = "gcc${lib.replaceStrings ["."] [""] majorMinorVersion}";

      pkg = lowPrio (wrapCC (callPackage ./default.nix {
@@ -24,7 +24,25 @@ let 
        profiledCompiler = false;

        libcCross = if stdenv.targetPlatform != stdenv.buildPlatform then args.libcCross else null;

        threadsCross = if stdenv.targetPlatform != stdenv.buildPlatform then threadsCross else { };

        isl = if stdenv.hostPlatform.isDarwin then null else isl_0_20;

        # do not allow version skew when cross-building gcc

        #

        # When `gcc` is cross-built (`build` != `target` && `host` == `target`)

        # `gcc` assumes that it has a compatible cross-compiler in the environment

        # that can build target libraries. Version of a cross-compiler has to

        # match the compiler being cross-built as libraries frequently use fresh

        # compiler features, like `-std=c++26` or target-specific types like

        # `_Bfloat16`.

        # Version mismatch causes build failures like:

        #     https://github.com/NixOS/nixpkgs/issues/351905

        #

        # Similar problems (but on a smaller scale) happen when a `gcc`

        # cross-compiler is built (`build` == `host` && `host` != `target`) built

        # by a mismatching version of a native compiler (`build` == `host` &&

        # `host` == `target`).

        #

        # Let's fix both problems by requiring the same compiler version for

        # cross-case.

        stdenv = if (stdenv.targetPlatform != stdenv.buildPlatform || stdenv.hostPlatform != stdenv.targetPlatform) && stdenv.cc.isGNU then pkgs."gcc${majorVersion}Stdenv" else stdenv;

      }));

    in

      lib.nameValuePair attrName pkg;