[PATCH] libstdc++: Make constexpr initializer_list a C++14 feature [PR113782]

[Tomasz Kaminski]

On Sun, Sep 20, 2026 at 12:19 PM Jonathan Wakely <jwakely.gcc@gmail.com>
wrote:

> On Fri, 18 Sept 2026 at 14:35, Albon Wu (BLOOMBERG/ 731 LEX)
> <awu574@bloomberg.net> wrote:
> >
> > Hi all,
> >
> > libstdc++ declares multiple methods on initializer_list as constexpr
> > unconditionally, but N3471 only added these in C++14, so in C++11 this is
> > non-conforming. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113782
> >
> > This also covers the private constructor of initializer_list, meaning it
> is
> > no longer a literal type in C++11. Some unrelated tests that used
> constexpr
> > initializer_list implicitly are retargeted to C++14.
> >
> > Built and tested on x86_64-pc-linux-gnu. Okay for trunk?
>
> Thanks for the patch. My concern with this approach is that it's a
> breaking change for anybody who is (inadvertently or intentionally)
> relying on this non-conforming behaviour. The benefit of rejecting the
> code is minimal - does it actually do any harm?
>
I do not see anything in C++11 standard that would specify compiler-magic
thjat cosntruct initializer_list out of braces is not usable at compile
time,
and I do not see how N3471 changed that.

>
> So I would prefer to keep these functions as constexpr for
> -std=gnu++11 and only change -std=c++11
>
>
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