tree 77d23d768605cd179dda411de751d1b70296ff24
parent 34a45c630d4c79af403661d267db42fbe7de1178
author Petr Hosek <phosek@chromium.org> 1548648774 +0000
committer Petr Hosek <phosek@chromium.org> 1548648774 +0000

[CMake] Use __libc_start_main rather than fopen when checking for C library

The check_library_exists CMake uses a custom symbol definition. This
is a problem when checking for C library symbols because Clang
recognizes many of them as builtins, and returns the
-Wbuiltin-requires-header (or -Wincompatible-library-redeclaration)
error. When building with -Werror which is the default, this causes
the check_library_exists check fail making the build think that C
library isn't available.

To avoid this issue, we should use a symbol that isn't recognized by
Clang and wouldn't cause the same issue. __libc_start_main seems like
reasonable choice that fits the bill.

Differential Revision: https://reviews.llvm.org/D57142

git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@352341 91177308-0d34-0410-b5e6-96231b3b80d8