On Wed, Aug 28, 2019 at 03:16:19PM -0700, Nick Desaulniers wrote: > That's a good reason IMO. IIRC, the -fno-builtin-* flags don't warn > if * is some unrecognized value, so -fno-builtin-setjmp may not > actually do anything, and you may need to scan the source (of clang or > llvm). -fno-builtin-foo makes the compiler not handle "foo" the same as it handles "__builtin_foo". If the compiler has no idea about "foo", well, that is exactly what it does then anyhow, so why would it warn :-) Segher