[Bug c++/67739] name clash between builtin functions and local variables when optimization is on

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67739

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
You are using -std=gnu89 by default and thus adhering to GNU extensions where
sincos is a known identifier.  We're missing to warn about this maybe(?).
Using -std=c89 should fix this as well (not verified).