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Check for __builtin_unreachable at configure time

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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.
This commit is contained in:
Elliot Ronaghan 2016-06-17 13:28:39 -07:00 • committed by Jason Evans
parent ae3314785b
commit 1167e9eff3
3 changed files with 29 additions and 16 deletions
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17
configure.ac
View file

@ -1038,6 +1038,23 @@ if test "x$enable_cache_oblivious" = "x1" ; then
fi
AC_SUBST([enable_cache_oblivious])
JE_COMPILABLE([a program using __builtin_unreachable], [
void foo (void) {
__builtin_unreachable();
}
], [
{
foo();
}
], [je_cv_gcc_builtin_unreachable])
if test "x${je_cv_gcc_builtin_ffsl}" = "xyes" ; then
AC_DEFINE([JEMALLOC_INTERNAL_UNREACHABLE], [__builtin_unreachable])
else
AC_DEFINE([JEMALLOC_INTERNAL_UNREACHABLE], [abort])
fi
dnl ============================================================================
dnl Check for __builtin_ffsl(), then ffsl(3), and fail if neither are found.
dnl One of those two functions should (theoretically) exist on all platforms