http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58994
--- Comment #4 from Jack Howarth <howarth at nitro dot med.uc.edu> --- Current llvm trunk is broken at the moment on darwin, but using a build from Oct 29th, I have no issues with the failing test case under clang... % /sw/opt/llvm-3.4/bin/clang -O1 -fsanitize=address -fno-builtin-memset -g -fdiagnostics-color=never -O0 -m64 global-overflow-1.c % ./a.out ================================================================= ==81836==ERROR: AddressSanitizer: global-buffer-overflow on address 0x000103d991ea at pc 0x103d98b76 bp 0x7fff5be686d0 sp 0x7fff5be686c8 READ of size 1 at 0x000103d991ea thread T0 ==81836==WARNING: Trying to symbolize code, but external symbolizer is not initialized! #0 0x103d98b75 (/Users/howarth/./a.out+0x100001b75) #1 0x7fff8a4237e0 (/usr/lib/system/libdyld.dylib+0x27e0) #2 0x0 0x000103d991ea is located 54 bytes to the left of global variable 'main.ZZZ' from 'global-overflow-1.c' (0x103d99220) of size 10 0x000103d991ea is located 0 bytes to the right of global variable 'main.YYY' from 'global-overflow-1.c' (0x103d991e0) of size 10 SUMMARY: AddressSanitizer: global-buffer-overflow ??:0 ?? Shadow bytes around the buggy address: 0x1000207b31e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x1000207b31f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x1000207b3200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x1000207b3210: 00 00 00 00 04 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 0x1000207b3220: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0x1000207b3230: 00 00 00 00 00 02 f9 f9 f9 f9 f9 f9 00[02]f9 f9 0x1000207b3240: f9 f9 f9 f9 00 02 f9 f9 f9 f9 f9 f9 00 00 00 00 0x1000207b3250: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x1000207b3260: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x1000207b3270: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x1000207b3280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Heap right redzone: fb Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack partial redzone: f4 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 ASan internal: fe ==81836==ABORTING