clang -O0            f(INT_MAX) = 0
clang -O2            f(INT_MAX) = 1
clang -O2 -fwrapv    f(INT_MAX) = 0
with -ftrapv at -O0: exit code -4 (SIGILL is 4, SIGTRAP is 5, so -4 or -5 means the overflow trapped)
