The comparison "_dispatch_hw_config.cc_max_active < 0” is of an unsigned value and thus never true, the attached patch uses and checks failure of sysconf() properly instead. Cheers, Joakim Index: src/queue.c =================================================================== --- src/queue.c (revision 197) +++ src/queue.c (working copy) @@ -474,12 +474,13 @@ _dispatch_hw_config.cc_max_physical = _dispatch_hw_config.cc_max_active; #elif HAVE_SYSCONF && defined(_SC_NPROCESSORS_ONLN) - _dispatch_hw_config.cc_max_active = (int)sysconf(_SC_NPROCESSORS_ONLN); - if (_dispatch_hw_config.cc_max_active < 0) - _dispatch_hw_config.cc_max_active = 1; + int ret; + + ret = (int)sysconf(_SC_NPROCESSORS_ONLN); + _dispatch_hw_config.cc_max_logical = _dispatch_hw_config.cc_max_physical = - _dispatch_hw_config.cc_max_active; + _dispatch_hw_config.cc_max_active = (ret < 0) ? 1 : ret; #else #warning "_dispatch_queue_set_width_init: no supported way to query CPU count" _dispatch_hw_config.cc_max_logical =