[Bug libstdc++/95765] std::vector should be built without warnings with -Wconversion and/or -Wsystem-headers

[redboltz at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95765

--- Comment #4 from Takatoshi Kondo <redboltz at gmail dot com> ---
Thank you for fixing the warnings.

> Users should not be routinely using -Wsystem-headers to find problems with their own code (that defeats the entire purpose of suppressing warnings in system headers).
>
> I've fixed some warnings in libstdc++ code, but the real problem here is Bug 43167 (and Bug 43167 comment 17 has almost exactly the same example).

I agree. If warnings relate to templates would be reported without
`-Wsystem-headers`, it is ideal.