--- 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);