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--- a/src/corelib/thread/qthread_unix.cpp.orig 2015-11-23 19:05:40.000000000 +0100
+++ b/src/corelib/thread/qthread_unix.cpp 2015-11-24 11:22:31.000000000 +0100
@@ -79,6 +79,7 @@
#endif
+#include <sys/resource.h> // getrlimit/setrlimit
#if defined(Q_OS_MAC)
# ifdef qDebug
# define old_qDebug qDebug
# undef qDebug
@@ -649,6 +650,43 @@
#endif // QT_HAS_THREAD_PRIORITY_SCHEDULING
+ if (d->stackSize == 0) {
+ // Fix the default (too small) stack size for threads on OS X,
+ // which also affects the thread pool.
+ // See also:
+ // https://bugreports.qt.io/browse/QTBUG-2568
+ // This fix can also be found in Chromium:
+ // https://chromium.googlesource.com/chromium/src.git/+/master/base/threading/platform_thread_mac.mm#186
+
+ // The Mac OS X default for a pthread stack size is 512kB.
+ // Libc-594.1.4/pthreads/pthread.c's pthread_attr_init uses
+ // DEFAULT_STACK_SIZE for this purpose.
+ //
+ // 512kB isn't quite generous enough for some deeply recursive threads that
+ // otherwise request the default stack size by specifying 0. Here, adopt
+ // glibc's behavior as on Linux, which is to use the current stack size
+ // limit (ulimit -s) as the default stack size. See
+ // glibc-2.11.1/nptl/nptl-init.c's __pthread_initialize_minimal_internal. To
+ // avoid setting the limit below the Mac OS X default or the minimum usable
+ // stack size, these values are also considered. If any of these values
+ // can't be determined, or if stack size is unlimited (ulimit -s unlimited),
+ // stack_size is left at 0 to get the system default.
+ //
+ // Mac OS X normally only applies ulimit -s to the main thread stack. On
+ // contemporary OS X and Linux systems alike, this value is generally 8MB
+ // or in that neighborhood.
+ size_t default_stack_size = 0;
+ struct rlimit stack_rlimit;
+ if (pthread_attr_getstacksize(&attr, &default_stack_size) == 0 &&
+ getrlimit(RLIMIT_STACK, &stack_rlimit) == 0 &&
+ stack_rlimit.rlim_cur != RLIM_INFINITY) {
+ default_stack_size =
+ std::max(std::max(default_stack_size,
+ static_cast<size_t>(PTHREAD_STACK_MIN)),
+ static_cast<size_t>(stack_rlimit.rlim_cur));
+ }
+ d->stackSize = default_stack_size;
+ }
if (d->stackSize > 0) {
#if defined(_POSIX_THREAD_ATTR_STACKSIZE) && (_POSIX_THREAD_ATTR_STACKSIZE-0 > 0)
int code = pthread_attr_setstacksize(&attr, d->stackSize);
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