[PATCH] PR libstdc++/84773 use aligned alloc functions for FreeBSD and MinGW cross-compilers

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

Cross-compilers for FreeBSD and MinGW do not currently check for
aligned_alloc, posix_memalign, _aligned_malloc etc which are used by
native compilers when available. This omission caused bootstrap failures
for FreeBSD cross-compilers, and caused ABI differences for MinGW due
to a different implementation of operator new(size_t, align_val_t).

Also add a using-declaration for aligned_alloc in namespace std for
C++17 support.

        PR libstdc++/84773
        PR libstdc++/83662
        * crossconfig.m4: Check for aligned_alloc etc. on freebsd and mingw32.
        * configure: Regenerate.
        * include/c_global/cstdlib [_GLIBCXX_HAVE_ALIGNED_ALLOC]
        (aligned_alloc): Add using-declaration.
        * testsuite/18_support/aligned_alloc/aligned_alloc.cc: New test.

Tested powerpc64le-linux, and by building cross-compilers for
x86_64-unknown-freebsd11.0 and x86_64-w64-mingw32. Committed to trunk,
backport to gcc-7-branch to follow.

Attachment: patch.txt
Description: Text document