stack guard - use __builtin_frame_address(0) Pointers on the stack are pretty whack. But clang builtins, they got yo' back. Fixes: 258970199 (: or it'll get re-filed :) Test: libbinderthreadstateutils_test Change-Id: I4a7af39c680562a1b7a7c2c71c54eb371d857d5e