[RFC] libstdc++: fix declaration and definition mismatch for _GLIBCXX20_CONSTEXPR

[Jonathan Wakely]

On Mon, 19 May 2025 at 12:09, Alexey Lapshin
<alexey.lapshin@espressif.com> wrote:
>
> Thanks for the quick response,
>
> I just want to save some space for embedded apps that are using c++
> Related issue is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93008
> So, I want to drop "constexpr" for templates.

That would be non-conforming though, so we absolutely can't do that.

> I'm not familiar with the libstdc++ source code and coding style.
> Is having mixed declarations and definitions intentional in libstdc++?

Do you mean defining some functions inline in the class body, instead
of only declaring them there and defining them all outside the class
body?
Yes, that's intentional, and IMHO a fairly conventional style for C++ classes.