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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/86369] constexpr const char* comparison fails
Date: Fri, 04 Nov 2022 13:27:19 +0000 [thread overview]
Message-ID: <bug-86369-4-U1kNVuzfWZ@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-86369-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86369
--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Aaron Ballman from comment #9)
> Doesn't [expr.eq] make it unspecified though?
Will defer that answer to Jason.
But please have a look at the comment 6 testcase. I strongly hope that
constexpr const char *p = "abc";
constexpr const char *q = p;
static_assert (p == q, "");
doesn't actually mean the string literal is evaluated multiple times, because
if it would be, then one pretty much can't use string literals for anything
reliably.
I bet the wording in there is for the
constexpr const char *r = "abc";
constexpr const char *s = "abc";
case, where the standard doesn't force implementations to unify same string
literals within the same TU but allows it (and also allows say tail merging of
them). From what I can see in the LLVM constant expression evaluation
behavior, it doesn't track what comes from which evaluation of a string literal
(GCC doesn't track that either) and just assumes that it could be different
evaluation, while GCC assumes it is not.
next prev parent reply other threads:[~2022-11-04 13:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-86369-4@http.gcc.gnu.org/bugzilla/>
2021-08-05 4:43 ` pinskia at gcc dot gnu.org
2021-08-05 15:24 ` redi at gcc dot gnu.org
2021-08-05 15:30 ` jakub at gcc dot gnu.org
2021-08-05 18:09 ` jakub at gcc dot gnu.org
2021-08-06 7:27 ` rguenth at gcc dot gnu.org
2022-01-18 13:18 ` jason at gcc dot gnu.org
2022-11-04 13:10 ` aaron at aaronballman dot com
2022-11-04 13:27 ` jakub at gcc dot gnu.org [this message]
2022-11-04 13:53 ` aaron at aaronballman dot com
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