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From: "pdimov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/102350] __builtin_source_location not available in earlier
 language modes
Date: Thu, 16 Sep 2021 10:24:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102350

--- Comment #10 from Peter Dimov <pdimov at gmail dot com> ---
(In reply to Jakub Jelinek from comment #9)
> That would be an aliasing violation.
> The artificial vars created by __builtin_source_location have the
> std::source_location::__impl type, so accessing those using some other
> dynamic type is invalid.

In that case, the only valid way to use the result of __builtin_source_loca=
tion
would just be std::source_location itself. :-/

I wonder whether there's a conformance problem in making it available. It's
true that the identifier `source_location` isn't reserved, but only programs
that include `<source_location>` can tell the difference, and these programs
(assuming they existed and worked) will probably be broken anyway because n=
ow
they'll be including the standard header instead of their own.=