https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102769
--- Comment #2 from Zhendong Su <zhendong.su at inf dot ethz.ch> --- Interesting --- it was missed by clang-10 sanitizers and the CompCert interpreter (a pretty rare occurrence): [565] % ccomp -interp -fall small.c small.c:13: warning: implicit declaration of function '__builtin_abort' is invalid in C99 [-Wimplicit-function-declaration] small.c:13: warning: '__builtin_abort' is declared without a function prototype Time 114: program terminated (exit code = 0) [566] % clang-10 -Xclang -disable-llvm-optzns -w -m64 -O0 -fwrapv -ftrapv -fsanitize=undefined,address small.c; ./a.out [567] % clang-10 -pie -fPIE -pie -Xclang -disable-llvm-optzns -w -O0 -m64 -fsanitize=memory small.c; ./a.out [568] %