[Bug middle-end/104854] -Wstringop-overread should not warn for strnlen, strndup and strncmp

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104854

--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
It would be useful to separate these warnings into multiple levels: level 1 for
invalid code, and higher levels for suspicious (or pointless) code, similarly
to -Wformat-overflow.