http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55289
--- Comment #27 from Jack Howarth <howarth at nitro dot med.uc.edu> 2012-11-14 16:06:10 UTC --- The error in mach_override.c occurs for the use-after-free.c test case at... Replacing function at 0x1119ef630 First 16 bytes of the function: 48 8d 5 11 4f b 0 53 48 8d 5f e0 48 89 77 90 To disassemble, save the following function as disas.c and run: gcc -c disas.c && gobjdump -d disas.o The first 16 bytes of the original function will start after four nop instructions. void foo() { asm volatile("nop;nop;nop;nop;"); asm volatile(".byte 0x48, 0x8d, 0x5, 0x11, 0x4f, 0xb, 0x0, 0x53;"); asm volatile(".byte 0x48, 0x8d, 0x5f, 0xe0, 0x48, 0x89, 0x77, 0x90;"); } Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 8d FAIL Matching: 48 8d FAIL Matching: 48 8d FAIL Matching: 48 8d FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 8d FAIL Matching: 48 8d FAIL Matching: 48 FAIL Matching: 48 8d FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 FAIL Matching: 48 8d FAIL mach_override: some instructions unknown! Need to update mach_override.c overridePossible = false @299 err = f8000001 ../../../../gcc-4.8-20121114/libsanitizer/interception/mach_override/mach_override.c:308 err = f8000001 ../../../../gcc-4.8-20121114/libsanitizer/interception/mach_override/mach_override.c:321 err = f8000001 ../../../../gcc-4.8-20121114/libsanitizer/interception/mach_override/mach_override.c:327 err = f8000001 ../../../../gcc-4.8-20121114/libsanitizer/interception/mach_override/mach_override.c:340 err = f8000001 ../../../../gcc-4.8-20121114/libsanitizer/interception/mach_override/mach_override.c:345 First 16 bytes of the function after slicing: 48 8d 5 11 4f b 0 53 48 8d 5f e0 48 89 77 90