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.
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configure.ac
17
configure.ac
@ -1050,6 +1050,23 @@ if test "x$enable_cache_oblivious" = "x1" ; then
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fi
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AC_SUBST([enable_cache_oblivious])
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JE_COMPILABLE([a program using __builtin_unreachable], [
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void foo (void) {
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__builtin_unreachable();
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}
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], [
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{
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foo();
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}
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], [je_cv_gcc_builtin_unreachable])
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if test "x${je_cv_gcc_builtin_ffsl}" = "xyes" ; then
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AC_DEFINE([JEMALLOC_INTERNAL_UNREACHABLE], [__builtin_unreachable])
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else
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AC_DEFINE([JEMALLOC_INTERNAL_UNREACHABLE], [abort])
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fi
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dnl ============================================================================
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dnl Check for __builtin_ffsl(), then ffsl(3), and fail if neither are found.
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dnl One of those two functions should (theoretically) exist on all platforms
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@ -188,6 +188,12 @@
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/* TLS is used to map arenas and magazine caches to threads. */
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#undef JEMALLOC_TLS
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/*
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* Used to mark unreachable code to quiet "end of non-void" compiler warnings.
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* Don't use this directly; instead use unreachable() from util.h
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*/
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#undef JEMALLOC_INTERNAL_UNREACHABLE
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/*
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* ffs*() functions to use for bitmapping. Don't use these directly; instead,
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* use ffs_*() from util.h.
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@ -61,30 +61,20 @@
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# define JEMALLOC_CC_SILENCE_INIT(v)
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#endif
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#define JEMALLOC_GNUC_PREREQ(major, minor) \
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(!defined(__clang__) && \
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(__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor))))
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#ifndef __has_builtin
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# define __has_builtin(builtin) (0)
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#endif
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#define JEMALLOC_CLANG_HAS_BUILTIN(builtin) \
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(defined(__clang__) && __has_builtin(builtin))
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#ifdef __GNUC__
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# define likely(x) __builtin_expect(!!(x), 1)
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# define unlikely(x) __builtin_expect(!!(x), 0)
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# if JEMALLOC_GNUC_PREREQ(4, 6) || \
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JEMALLOC_CLANG_HAS_BUILTIN(__builtin_unreachable)
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# define unreachable() __builtin_unreachable()
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# else
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# define unreachable() abort()
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# endif
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#else
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# define likely(x) !!(x)
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# define unlikely(x) !!(x)
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# define unreachable() abort()
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#endif
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#if !defined(JEMALLOC_INTERNAL_UNREACHABLE)
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# error JEMALLOC_INTERNAL_UNREACHABLE should have been defined by configure
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#endif
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#define unreachable() JEMALLOC_INTERNAL_UNREACHABLE()
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#include "jemalloc/internal/assert.h"
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/* Use to assert a particular configuration, e.g., cassert(config_debug). */
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