Re: Reördering SVt_* constants; "internal" SV type

On Thu, 18 Jun 2026 at 12:45, Paul "LeoNerd" Evans
<[email protected]> wrote:
>   An SV should be treated as a Perl-visible scalar
>     if SvTYPE(sv) <= SVt_PVXX

Yeah, this would be nice to have.

>   SVt_INVLIST   is not a perl-visible scalar, in fact should not be
>                 visible to any perl code anywhere for any reason, but
>                 it sorts right after SVt_PV and before SVt_PVIV and is
>                 thus accidentally included in the above scalar test

I think it's located there because it's sort of a PV under the hood.
Not sure offhand if moving it out of the "Perl-visible scalar"
grouping would break anything.

> I know there are some ordering constraints involved in the SvTYPE
> values, but I don't believe it would be too problematic to move
> SVt_PVLV to just after SVt_PVMG (and thus allow a contiguous range for
> scalars).

Might need to adjust the handful of places that do "type <= SVt_PVLV"
and similar.

Are there some code paths in which SVt_PVGV is also treated like a
"Perl-visible scalar" or at least would be nice to have it covered by
a "SvTYPE(sv) <= some-other-value" check?