[Bug c/78981] Sign extension bug when stdlib is not explicitly included while using getenv on amd64.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78981

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
You should be getting an implicit function declared warning with -Wextra -Wall
.