tree 953c2a018738b1837ad492f24dda9e59008845d3
parent a6a8e40f7d24ee9f4f6abf1c03e1e0d7e3763084
author Elliot Ronaghan <ronawho@gmail.com> 1466195319 -0700
committer Jason Evans <jasone@canonware.com> 1474911877 -0700

Check for __builtin_unreachable at configure time

Add a configure check for __builtin_unreachable instead of basing its
availability on the __GNUC__ version. On OS X using gcc (a real gcc, not the
bundled version that's just a gcc front-end) leads to a linker assertion:

    https://github.com/jemalloc/jemalloc/issues/266

It turns out that this is caused by a gcc bug resulting from the use of
__builtin_unreachable():

    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57438

To work around this bug, check that __builtin_unreachable() actually works at
configure time, and if it doesn't use abort() instead. The check is based on
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57438#c21.

With this `make check` passes with a homebrew installed gcc-5 and gcc-6.