http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51258
--- Comment #17 from Uros Bizjak <ubizjak at gmail dot com> 2011-12-06 19:29:09 UTC --- (In reply to comment #16) > Created attachment 26009 [details] > log of FAIL: gcc.dg/simulate-thread/atomic-load-int128.c -O1 -g thread > simulation test failure on x86_64-apple-darwin11 Can you try with increased timeout value? In testsuite/lib/gcc-simulate-thread.exp find following line: # Set timeout to 10 seconds due to huge amount of generated log. remote_expect target 10 { and increase 10. If this fails, you should check if generated executable runs OK outside of the debugger.