llvmPackages_15, llvmPackages_16: Make the pkgsLLVM.stdenv work

What changed:

* Fixed crtbeginS.o and crtendS.o missing
  (they may or may not be called crt{begin_end},{,_shared}.

* Fixed implicit function declaration causing build errors for various
  builds by supplying -Wno-implicit-function-declaration.

* Fixed __cxxabi_config.h missing, by adding -I${cxxabi}/include/c++/v1
  in the wrapper.

* Fixed libcxx failing to build due to missing libunwind symbols by
  including libunwind as a buildInput, and setting
  -DLIBCXX_ADDITIONAL_LIBRARIES=unwind for stdenv.hostPlatform.useLLVM == true.

* libcxxabi wants to find libunwind at libunwind_shared.so, so symlink
  it there in libunwind.

* llvmPackages_16.libcxxabi: Pass -nostdlib via CMAKE_*_LINKER_FLAGS

  Without this flag, the link of libcxxabi.so tries to pull in libgcc and
  friends, from the clang compiler driver.

* Drop unneeded musl hack patch from libcxx.

* Pass -Wno-error=implicit-function-declaration only to compiler-rt

  See LLVM forum discussion:

  https://discourse.llvm.org/t/configure-script-breakage-with-the-new-werror-implicit-function-declaration/65213

  In summary, LLVM 16 made implicit function declaration an error. This
  happens a lot in configure scripts which can break things.

* llvmPackages_16: !isDarwin: Supply -DLIBCXX_ABI_USE_LLVM_UNWINDER=On

  Otherwise it fails with various undefined references to _Unwind_*
  functions: (full list: _Unwind_DeleteException _Unwind_GetIP
  _Unwind_GetLanguageSpecificData _Unwind_GetRegionStart
  _Unwind_RaiseException _Unwind_Resume _Unwind_SetGR _Unwind_SetIP).

* 16.libcxxabi: Only pass -nostdlib for useLLVM and Darwin builds

What was tested:

* x86_64-linux, aarch64-linux, the stdenv builds.
  * Additionally I was able to get nix to build, with an overlay to fix
    a couple of minor issues in downstream packages (overlay supplied in
    PR #246577.

* aarch64-darwin fails spuriously in a single LLVM test
  strip-preserve-atime.test checking atime timestamps.

* The same for pkgsLLVM with llvmPackages = llvmPackages_15.

Signed-off-by: Peter Waller <p@pwaller.net>

1 files changed, 16 insertions, 3 deletions

diff --git a/pkgs/development/compilers/llvm/16/compiler-rt/default.nix b/pkgs/development/compilers/llvm/16/compiler-rt/default.nix
index aa248c0e60e..fc0d7533c99 100644
--- a/pkgs/development/compilers/llvm/16/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/16/compiler-rt/default.nix
@@ -32,9 +32,16 @@ stdenv.mkDerivation {
     ++ lib.optional stdenv.isDarwin xcbuild.xcrun;
   buildInputs = lib.optional stdenv.hostPlatform.isDarwin libcxxabi;
 
-  env.NIX_CFLAGS_COMPILE = toString [
+  env.NIX_CFLAGS_COMPILE = toString ([
     "-DSCUDO_DEFAULT_OPTIONS=DeleteSizeMismatch=0:DeallocationTypeMismatch=0"
-  ];
+  ] ++ lib.optionals (!haveLibc) [
+    # The compiler got stricter about this, and there is a usellvm patch below
+    # which patches out the assert include causing an implicit definition of
+    # assert. It would be nicer to understand why compiler-rt thinks it should
+    # be able to #include <assert.h> in the first place; perhaps it's in the
+    # wrong, or perhaps there is a way to provide an assert.h.
+    "-Wno-error=implicit-function-declaration"
+  ]);
 
   cmakeFlags = [
     "-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON"
@@ -102,7 +109,7 @@ stdenv.mkDerivation {
   '' + lib.optionalString stdenv.isDarwin ''
     substituteInPlace cmake/config-ix.cmake \
       --replace 'set(COMPILER_RT_HAS_TSAN TRUE)' 'set(COMPILER_RT_HAS_TSAN FALSE)'
-  '' + lib.optionalString (useLLVM) ''
+  '' + lib.optionalString (useLLVM && !haveLibc) ''
     substituteInPlace lib/builtins/int_util.c \
       --replace "#include <stdlib.h>" ""
     substituteInPlace lib/builtins/clear_cache.c \
@@ -117,6 +124,12 @@ stdenv.mkDerivation {
   '' + 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
+    # Note the history of crt{begin,end}S in previous versions of llvm in nixpkg:
+    # The presence of crtbegin_shared has been added and removed; it's possible
+    # people have added/removed it to get it working on their platforms.
+    # Try each in turn for now.
+    ln -s $out/lib/*/clang_rt.crtbegin-*.o $out/lib/crtbeginS.o
+    ln -s $out/lib/*/clang_rt.crtend-*.o $out/lib/crtendS.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
   '' + lib.optionalString doFakeLibgcc ''