Summary:
system_error::message() uses `strerror` for the generic and system categories. This function is not thread safe.
The fix is to use `strerror_r`. It has been available since 2001 for GNU libc and since BSD 4.4 on FreeBSD/OS X.
On platforms with GNU libc the extended version is used which always returns a valid string, even if an error occurs.
In single-threaded builds `strerror` is still used.
See https://llvm.org/bugs/show_bug.cgi?id=25598
Reviewers: majnemer, mclow.lists
Subscribers: erik65536, cfe-commits, emaste
Differential Revision: http://reviews.llvm.org/D20903
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@272633 91177308-0d34-0410-b5e6-96231b3b80d8
