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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 a6a8e40f7d
commit d1207f0d37
3 changed files with 29 additions and 16 deletions
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17
configure.ac
View File

@ -1050,6 +1050,23 @@ if test "x$enable_cache_oblivious" = "x1" ; then
fi fi
AC_SUBST([enable_cache_oblivious]) AC_SUBST([enable_cache_oblivious])
JE_COMPILABLE([a program using __builtin_unreachable], [
void foo (void) {
__builtin_unreachable();
}
], [
{
foo();
}
], [je_cv_gcc_builtin_unreachable])
if test "x${je_cv_gcc_builtin_ffsl}" = "xyes" ; then
AC_DEFINE([JEMALLOC_INTERNAL_UNREACHABLE], [__builtin_unreachable])
else
AC_DEFINE([JEMALLOC_INTERNAL_UNREACHABLE], [abort])
fi
dnl ============================================================================ dnl ============================================================================
dnl Check for __builtin_ffsl(), then ffsl(3), and fail if neither are found. 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 dnl One of those two functions should (theoretically) exist on all platforms

6
include/jemalloc/internal/jemalloc_internal_defs.h.in
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@ -188,6 +188,12 @@
/* TLS is used to map arenas and magazine caches to threads. */ /* TLS is used to map arenas and magazine caches to threads. */
#undef JEMALLOC_TLS #undef JEMALLOC_TLS
/*
* Used to mark unreachable code to quiet "end of non-void" compiler warnings.
* Don't use this directly; instead use unreachable() from util.h
*/
#undef JEMALLOC_INTERNAL_UNREACHABLE
/* /*
* ffs*() functions to use for bitmapping. Don't use these directly; instead, * ffs*() functions to use for bitmapping. Don't use these directly; instead,
* use ffs_*() from util.h. * use ffs_*() from util.h.

22
include/jemalloc/internal/util.h
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@ -61,30 +61,20 @@
# define JEMALLOC_CC_SILENCE_INIT(v) # define JEMALLOC_CC_SILENCE_INIT(v)
#endif #endif
#define JEMALLOC_GNUC_PREREQ(major, minor) \
(!defined(__clang__) && \
(__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor))))
#ifndef __has_builtin
# define __has_builtin(builtin) (0)
#endif
#define JEMALLOC_CLANG_HAS_BUILTIN(builtin) \
(defined(__clang__) && __has_builtin(builtin))
#ifdef __GNUC__ #ifdef __GNUC__
# define likely(x) __builtin_expect(!!(x), 1) # define likely(x) __builtin_expect(!!(x), 1)
# define unlikely(x) __builtin_expect(!!(x), 0) # define unlikely(x) __builtin_expect(!!(x), 0)
# if JEMALLOC_GNUC_PREREQ(4, 6) || \
JEMALLOC_CLANG_HAS_BUILTIN(__builtin_unreachable)
# define unreachable() __builtin_unreachable()
# else
# define unreachable() abort()
# endif
#else #else
# define likely(x) !!(x) # define likely(x) !!(x)
# define unlikely(x) !!(x) # define unlikely(x) !!(x)
# define unreachable() abort()
#endif #endif
#if !defined(JEMALLOC_INTERNAL_UNREACHABLE)
# error JEMALLOC_INTERNAL_UNREACHABLE should have been defined by configure
#endif
#define unreachable() JEMALLOC_INTERNAL_UNREACHABLE()
#include "jemalloc/internal/assert.h" #include "jemalloc/internal/assert.h"
/* Use to assert a particular configuration, e.g., cassert(config_debug). */ /* Use to assert a particular configuration, e.g., cassert(config_debug). */