{ lib, stdenv, targetPackages, fetchurl, fetchpatch, noSysDirs
, langC ? true, langCC ? true, langFortran ? false
, langAda ? false
, langObjC ? stdenv.targetPlatform.isDarwin
, langObjCpp ? stdenv.targetPlatform.isDarwin
, langD ? false
, langGo ? false
, reproducibleBuild ? true
, profiledCompiler ? false
, langJit ? false
, staticCompiler ? false
, enableShared ? stdenv.targetPlatform.hasSharedLibraries
, enableLTO ? stdenv.hostPlatform.hasSharedLibraries
, texinfo ? null
, perl ? null # optional, for texi2pod (then pod2man)
, gmp, mpfr, libmpc, gettext, which, patchelf, binutils
, isl ? null # optional, for the Graphite optimization framework.
, zlib ? null
, gnat-bootstrap ? null
, enableMultilib ? false
, enablePlugin ? stdenv.hostPlatform == stdenv.buildPlatform # Whether to support user-supplied plug-ins
, name ? "gcc"
, libcCross ? null
, threadsCross ? null # for MinGW
, withoutTargetLibc ? false
, gnused ? null
, cloog # unused; just for compat with gcc4, as we override the parameter on some places
, buildPackages
, callPackage
}:

# Note: this package is used for bootstrapping fetchurl, and thus
# cannot use fetchpatch! All mutable patches (generated by GitHub or
# cgit) that are needed here should be included directly in Nixpkgs as
# files.

# Make sure we get GNU sed.
assert stdenv.buildPlatform.isDarwin -> gnused != null;

# The go frontend is written in c++
assert langGo -> langCC;
assert langAda -> gnat-bootstrap != null;

# threadsCross is just for MinGW
assert threadsCross != {} -> stdenv.targetPlatform.isWindows;

# profiledCompiler builds inject non-determinism in one of the compilation stages.
# If turned on, we can't provide reproducible builds anymore
assert reproducibleBuild -> profiledCompiler == false;

with lib;
with builtins;

let majorVersion = "9";
    version = "${majorVersion}.5.0";

    inherit (stdenv) buildPlatform hostPlatform targetPlatform;

    patches = [
      ./fix-struct-redefinition-on-glibc-2.36.patch
      # Fix https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80431
      ../fix-bug-80431.patch
    ] ++ optional (targetPlatform != hostPlatform) ../libstdc++-target.patch
      ++ optional targetPlatform.isNetBSD ../libstdc++-netbsd-ctypes.patch
      ++ optional noSysDirs ../no-sys-dirs.patch
      ++ optional (noSysDirs && hostPlatform.isRiscV) ../no-sys-dirs-riscv-gcc9.patch
      /* ++ optional (hostPlatform != buildPlatform) (fetchpatch { # XXX: Refine when this should be applied
        url = "https://git.busybox.net/buildroot/plain/package/gcc/${version}/0900-remove-selftests.patch?id=11271540bfe6adafbc133caf6b5b902a816f5f02";
        sha256 = ""; # TODO: uncomment and check hash when available.
      }) */
      ++ optional langAda ../gnat-cflags.patch
      ++ optional langD ../libphobos.patch
      ++ optional langFortran ../gfortran-driving.patch
      ++ optional (targetPlatform.libc == "musl" && targetPlatform.isPower) ../ppc-musl.patch

      # Obtain latest patch with ../update-mcfgthread-patches.sh
      ++ optional (!withoutTargetLibc && targetPlatform.isMinGW && threadsCross.model == "mcf") ./Added-mcf-thread-model-support-from-mcfgthread.patch
      ;

    /* Cross-gcc settings (build == host != target) */
    crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";
    stageNameAddon = if withoutTargetLibc then "stage-static" else "stage-final";
    crossNameAddon = optionalString (targetPlatform != hostPlatform) "${targetPlatform.config}-${stageNameAddon}-";

    callFile = lib.callPackageWith {
      # lets
      inherit
        majorVersion
        version
        buildPlatform
        hostPlatform
        targetPlatform
        patches
        crossMingw
        stageNameAddon
        crossNameAddon
      ;
      # inherit generated with 'nix eval --json --impure --expr "with import ./. {}; lib.attrNames (lib.functionArgs gcc9.cc.override)" | jq '.[]' --raw-output'
      inherit
        binutils
        buildPackages
        cloog
        withoutTargetLibc
        enableLTO
        enableMultilib
        enablePlugin
        enableShared
        fetchpatch
        fetchurl
        gettext
        gmp
        gnat-bootstrap
        gnused
        isl
        langAda
        langC
        langCC
        langD
        langFortran
        langGo
        langJit
        langObjC
        langObjCpp
        lib
        libcCross
        libmpc
        mpfr
        name
        noSysDirs
        patchelf
        perl
        profiledCompiler
        reproducibleBuild
        staticCompiler
        stdenv
        targetPackages
        texinfo
        threadsCross
        which
        zip
        zlib
      ;
    };

in

lib.pipe (stdenv.mkDerivation ({
  pname = "${crossNameAddon}${name}";
  inherit version;

  builder = ../builder.sh;

  src = fetchurl {
    url = "mirror://gcc/releases/gcc-${version}/gcc-${version}.tar.xz";
    sha256 = "13ygjmd938m0wmy946pxdhz9i1wq7z4w10l6pvidak0xxxj9yxi7";
  };

  inherit patches;

  outputs = [ "out" "man" "info" ] ++ lib.optional (!langJit) "lib";
  setOutputFlags = false;
  NIX_NO_SELF_RPATH = true;

  libc_dev = stdenv.cc.libc_dev;

  hardeningDisable = [ "format" "pie" ];

  postPatch = ''
    configureScripts=$(find . -name configure)
    for configureScript in $configureScripts; do
      patchShebangs $configureScript
    done
  ''
  # This should kill all the stdinc frameworks that gcc and friends like to
  # insert into default search paths.
  + lib.optionalString hostPlatform.isDarwin ''
    substituteInPlace gcc/config/darwin-c.c \
      --replace 'if (stdinc)' 'if (0)'

    substituteInPlace libgcc/config/t-slibgcc-darwin \
      --replace "-install_name @shlib_slibdir@/\$(SHLIB_INSTALL_NAME)" "-install_name ''${!outputLib}/lib/\$(SHLIB_INSTALL_NAME)"

    substituteInPlace libgfortran/configure \
      --replace "-install_name \\\$rpath/\\\$soname" "-install_name ''${!outputLib}/lib/\\\$soname"
  ''
  + (
    lib.optionalString (targetPlatform != hostPlatform || stdenv.cc.libc != null)
      # On NixOS, use the right path to the dynamic linker instead of
      # `/lib/ld*.so'.
      (let
        libc = if libcCross != null then libcCross else stdenv.cc.libc;
      in
        (
        '' echo "fixing the \`GLIBC_DYNAMIC_LINKER', \`UCLIBC_DYNAMIC_LINKER', and \`MUSL_DYNAMIC_LINKER' macros..."
           for header in "gcc/config/"*-gnu.h "gcc/config/"*"/"*.h
           do
             grep -q _DYNAMIC_LINKER "$header" || continue
             echo "  fixing \`$header'..."
             sed -i "$header" \
                 -e 's|define[[:blank:]]*\([UCG]\+\)LIBC_DYNAMIC_LINKER\([0-9]*\)[[:blank:]]"\([^\"]\+\)"$|define \1LIBC_DYNAMIC_LINKER\2 "${libc.out}\3"|g' \
                 -e 's|define[[:blank:]]*MUSL_DYNAMIC_LINKER\([0-9]*\)[[:blank:]]"\([^\"]\+\)"$|define MUSL_DYNAMIC_LINKER\1 "${libc.out}\2"|g'
           done
        ''
        + lib.optionalString (targetPlatform.libc == "musl")
        ''
            sed -i gcc/config/linux.h -e '1i#undef LOCAL_INCLUDE_DIR'
        ''
        ))
    )
      + lib.optionalString targetPlatform.isAvr ''
          makeFlagsArray+=(
             'LIMITS_H_TEST=false'
          )
        '';

  # kludge to prevent a mass-rebuild; will be removed in a PR sent to staging
  crossStageStatic = withoutTargetLibc;

  inherit noSysDirs staticCompiler
    libcCross crossMingw;

  inherit (callFile ../common/dependencies.nix { })
    depsBuildBuild nativeBuildInputs depsBuildTarget buildInputs depsTargetTarget;

  NIX_LDFLAGS = lib.optionalString  hostPlatform.isSunOS "-lm";

  preConfigure = callFile ../common/pre-configure.nix { };

  dontDisableStatic = true;

  configurePlatforms = [ "build" "host" "target" ];

  configureFlags = callFile ../common/configure-flags.nix { };

  targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;

  buildFlags = optional
    (targetPlatform == hostPlatform && hostPlatform == buildPlatform)
    (if profiledCompiler then "profiledbootstrap" else "bootstrap");

  # https://gcc.gnu.org/PR109898
  enableParallelInstalling = false;

  inherit (callFile ../common/strip-attributes.nix { })
    stripDebugList
    stripDebugListTarget
    preFixup;

  # https://gcc.gnu.org/install/specific.html#x86-64-x-solaris210
  ${if hostPlatform.system == "x86_64-solaris" then "CC" else null} = "gcc -m64";

  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
  # library headers and binaries, regarless of the language being compiled.
  #
  # Likewise, the LTO code doesn't find zlib.
  #
  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
  # compiler (after the specs for the cross-gcc are created). Having
  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.

  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
    ++ optional (zlib != null) zlib
  ));

  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath (optional (zlib != null) zlib));

  inherit (callFile ../common/extra-target-flags.nix { })
    EXTRA_FLAGS_FOR_TARGET
    EXTRA_LDFLAGS_FOR_TARGET
    ;

  passthru = {
    inherit langC langCC langObjC langObjCpp langAda langFortran langGo langD version;
    isGNU = true;
    hardeningUnsupportedFlags = [ "fortify3" ];
  };

  enableParallelBuilding = true;
  inherit enableShared enableMultilib;

  meta = {
    inherit (callFile ../common/meta.nix { })
      homepage
      license
      description
      longDescription
      platforms
      maintainers
    ;
    badPlatforms = [ "aarch64-darwin" ];
  };
}


// optionalAttrs (enableMultilib) { dontMoveLib64 = true; }
)
) [
  (callPackage ../common/libgcc.nix   { inherit version langC langCC langJit targetPlatform hostPlatform withoutTargetLibc enableShared; })
]