[Bug c++/79452] Provide builtin to detect compile-time execution

[gonzalobg88 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79452

--- Comment #8 from gnzlbg <gonzalobg88 at gmail dot com> ---
Eric your concerns and suggestions make sense. Changing the signature of the
functions using something like __ctfe__ and probably anything that would use
those sounds like a major ABI breaking change though. I do not think we can
find a better solution though, but it makes me reconsider whether we really
need this. We do need something like this, but i don't know at what cost.