[Bug c/106018] Feature Request: Add function attribute fn_enter, and fn_exit

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106018

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
it's going to be "interesting" if the arguments or return types need
construction (C++).