[all-commits] [llvm/llvm-project] e321c8: C++/ObjC++: switch to gnu++17 as the default standard

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e321c8dd2cea8365045ed44ae1c3c00c6a977d2e
      https://github.com/llvm/llvm-project/commit/e321c8dd2cea8365045ed44ae1c3c00c6a977d2e
  Author: Fangrui Song <i at maskray.me>
  Date:   2022-09-07 (Wed, 07 Sep 2022)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/lib/Basic/LangStandards.cpp
    A clang/test/Preprocessor/lang-std.cpp
    R clang/test/Preprocessor/lang-std.cu
    M clang/test/lit.cfg.py
    M clang/test/lit.site.cfg.py.in

  Log Message:
  -----------
  C++/ObjC++: switch to gnu++17 as the default standard

Clang's default C++ standard is now `gnu++17` instead of `gnu++14`:
https://discourse.llvm.org/t/c-objc-switch-to-gnu-17-as-the-default-dialect/64360

* CUDA/HIP are unchanged: C++14 from D103221.
* Sony PS4/PS5 are unchanged: https://discourse.llvm.org/t/c-objc-switch-to-gnu-17-as-the-default-dialect/64360/6
* lit feature `default-std-cxx` is added to keep CLANG_DEFAULT_STD_CXX=xxx tests working.
  Whether the cmake variable should be retained is disccused in D133375.

Depends on D131464

Close https://github.com/llvm/llvm-project/issues/56946

Reviewed By: #clang-language-wg, aaron.ballman

Differential Revision: https://reviews.llvm.org/D131465