[all-commits] [llvm/llvm-project] 62ff9a: [OpenMP] Use Clang resource dir only in bootstrapp...

[Michael Kruse via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 62ff9ac4c68f48c089528105259c68943ab176de
      https://github.com/llvm/llvm-project/commit/62ff9ac4c68f48c089528105259c68943ab176de
  Author: Michael Kruse <llvm-project at meinersbur.de>
  Date:   2025-08-30 (Sat, 30 Aug 2025)

  Changed paths:
    M openmp/runtime/src/CMakeLists.txt

  Log Message:
  -----------
  [OpenMP] Use Clang resource dir only in bootstrapping build (#156018)

In an LLVM_ENABLE_PROJECTS=openmp build, the LLVM build tree in which
just-built Clang is available, but in contrast to an
LLVM_ENABLE_RUNTIMES=openmp build, is not the compiler that openmp is
built with (CMAKE_CXX_COMPILER). The latter compiler (which might also
be gcc) will not look into the resource directory of just-built Clang,
where the OpenMP headers are installed. There may not even be a
just-built Clang without LLVM_ENABLE_PROJECTS=clang.

We cannot add the OpenMP header output directory to the search path
which also include's Clang's internal headers that will conflict with
CMAKE_CXX_COMPILER's internal headers. The only choice left is to use
what the OpenMP standalone build does: Use CMAKE_CURRENT_BINARY_DIR
which is added unconditionally to the header search path to compile
openmp itself.



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