--- 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);