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Implement a more reliable detection scheme for os_unfair_lock.

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The core issue here is the weak linking of the symbol, and in certain
environments--for instance, using the latest Xcode (8.1) with the latest
SDK (10.12)--os_unfair_lock may resolve even though you're compiling on
a host that doesn't support it (10.11).

We can use the availability macros to circumvent this problem, and
detect that we're not compiling for a target that is going to support
them and error out at compile time.  The other alternative is to do a
runtime check, but that presents issues for cross-compiling.
This commit is contained in:
John Szakmeister 2016-11-23 15:32:35 -05:00 committed by Jason Evans
parent e98a620c59
commit a05d4da4d8
1 changed files with 5 additions and 0 deletions
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5
configure.ac
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@ -1708,10 +1708,15 @@ dnl Check for os_unfair_lock operations as provided on Darwin.
JE_COMPILABLE([Darwin os_unfair_lock_*()], [
#include <os/lock.h>
#include <AvailabilityMacros.h>
], [
#if MAC_OS_X_VERSION_MIN_REQUIRED < 101200
#error "os_unfair_lock is not supported"
#else
os_unfair_lock lock = OS_UNFAIR_LOCK_INIT;
os_unfair_lock_lock(&lock);
os_unfair_lock_unlock(&lock);
#endif
], [je_cv_os_unfair_lock])
if test "x${je_cv_os_unfair_lock}" = "xyes" ; then
AC_DEFINE([JEMALLOC_OS_UNFAIR_LOCK], [ ])