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