{ stdenv, version, fetch, cmake, python3, llvm, libcxxabi }:

let

  useLLVM = stdenv.hostPlatform.useLLVM or false;
  bareMetal = stdenv.hostPlatform.parsed.kernel.name == "none";
  inherit (stdenv.hostPlatform) isMusl;

in

stdenv.mkDerivation rec {
  pname = "compiler-rt";
  inherit version;
  src = fetch pname "0d5j5l8phwqjjscmk8rmqn0i2i0abl537gdbkagl8fjpzy1gyjip";

  nativeBuildInputs = [ cmake python3 llvm ];
  buildInputs = stdenv.lib.optional stdenv.hostPlatform.isDarwin libcxxabi;

  NIX_CFLAGS_COMPILE = [
    "-DSCUDO_DEFAULT_OPTIONS=DeleteSizeMismatch=0:DeallocationTypeMismatch=0"
  ];

  cmakeFlags = [
    "-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON"
    "-DCMAKE_C_COMPILER_TARGET=${stdenv.hostPlatform.config}"
    "-DCMAKE_ASM_COMPILER_TARGET=${stdenv.hostPlatform.config}"
  ] ++ stdenv.lib.optionals (stdenv.isDarwin) [
    "-DDARWIN_macosx_OVERRIDE_SDK_VERSION=ON"
  ] ++ stdenv.lib.optionals (useLLVM || bareMetal || isMusl) [
    "-DCOMPILER_RT_BUILD_SANITIZERS=OFF"
    "-DCOMPILER_RT_BUILD_XRAY=OFF"
    "-DCOMPILER_RT_BUILD_LIBFUZZER=OFF"
    "-DCOMPILER_RT_BUILD_PROFILE=OFF"
  ] ++ stdenv.lib.optionals (useLLVM || bareMetal) [
    "-DCMAKE_C_COMPILER_WORKS=ON"
    "-DCMAKE_CXX_COMPILER_WORKS=ON"
    "-DCOMPILER_RT_BAREMETAL_BUILD=ON"
    "-DCMAKE_SIZEOF_VOID_P=${toString (stdenv.hostPlatform.parsed.cpu.bits / 8)}"
  ] ++ stdenv.lib.optionals (useLLVM) [
    "-DCOMPILER_RT_BUILD_BUILTINS=ON"
    "-DCMAKE_C_FLAGS=-nodefaultlibs"
    #https://stackoverflow.com/questions/53633705/cmake-the-c-compiler-is-not-able-to-compile-a-simple-test-program
    "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
  ] ++ stdenv.lib.optionals (bareMetal) [
    "-DCOMPILER_RT_OS_DIR=baremetal"
  ];

  outputs = [ "out" "dev" ];

  patches = [
    ./compiler-rt-codesign.patch # Revert compiler-rt commit that makes codesign mandatory
    ./compiler-rt-X86-support-extension.patch # Add support for i486 i586 i686 by reusing i386 config
  ]# ++ stdenv.lib.optional stdenv.hostPlatform.isMusl ./sanitizers-nongnu.patch
    ++ stdenv.lib.optional stdenv.hostPlatform.isAarch32 ./compiler-rt-armv7l.patch;


  # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
  # to get it, but they're unfree. Since LLVM is rather central to the stdenv, we patch out TSAN support so that Hydra
  # can build this. If we didn't do it, basically the entire nixpkgs on Darwin would have an unfree dependency and we'd
  # get no binary cache for the entire platform. If you really find yourself wanting the TSAN, make this controllable by
  # a flag and turn the flag off during the stdenv build.
  postPatch = stdenv.lib.optionalString (!stdenv.isDarwin) ''
    substituteInPlace cmake/builtin-config-ix.cmake \
      --replace 'set(X86 i386)' 'set(X86 i386 i486 i586 i686)'
  '' + stdenv.lib.optionalString stdenv.isDarwin ''
    substituteInPlace cmake/builtin-config-ix.cmake \
      --replace 'set(ARM64 arm64 arm64e)' 'set(ARM64)'
    substituteInPlace cmake/config-ix.cmake \
      --replace 'set(COMPILER_RT_HAS_TSAN TRUE)' 'set(COMPILER_RT_HAS_TSAN FALSE)'
  '' + stdenv.lib.optionalString (useLLVM) ''
    substituteInPlace lib/builtins/int_util.c \
      --replace "#include <stdlib.h>" ""
    substituteInPlace lib/builtins/clear_cache.c \
      --replace "#include <assert.h>" ""
    substituteInPlace lib/builtins/cpu_model.c \
      --replace "#include <assert.h>" ""
  '';

  # Hack around weird upsream RPATH bug
  postInstall = stdenv.lib.optionalString (stdenv.hostPlatform.isDarwin || stdenv.hostPlatform.isWasm) ''
    ln -s "$out/lib"/*/* "$out/lib"
  '' + stdenv.lib.optionalString (useLLVM) ''
    ln -s $out/lib/*/clang_rt.crtbegin-*.o $out/lib/crtbegin.o
    ln -s $out/lib/*/clang_rt.crtend-*.o $out/lib/crtend.o
    ln -s $out/lib/*/clang_rt.crtbegin_shared-*.o $out/lib/crtbeginS.o
    ln -s $out/lib/*/clang_rt.crtend_shared-*.o $out/lib/crtendS.o
  '';

  enableParallelBuilding = true;
}