[PATCH] D136712: Define _GNU_SOURCE for arm baremetal in C++ mode.

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added a comment.

Is this an upstream GCC behavior or a behavior from some gcc-none-eabi distributions?
GCC's C++ mode defines `_GNU_SOURCE` historically due to a libstdc++ limitation https://gcc.gnu.org/onlinedocs/libstdc++/faq.html#faq.predefined and nowadays "the ship has sailed" and many targets do the same for compatibility.
For C, most targets don't force defining `_GNU_SOURCE`.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D136712/new/

https://reviews.llvm.org/D136712