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From: "aaron at aaronballman dot com" <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 13:10:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D86369

Aaron Ballman <aaron at aaronballman dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aaron at aaronballman dot =
com

--- Comment #9 from Aaron Ballman <aaron at aaronballman dot com> ---
(In reply to Jason Merrill from comment #8)
> (In reply to Nicolas Lesser from comment #1)
> > For clarity, b1 shouldn't compile.
> >=20
> > [lex.string]p16 says: "whether successive evaluations of a string-liter=
al
> > yield the same or a different object is unspecified."
> >=20
> > [expr.const]p2 says: "An expression e is a core constant expression unl=
ess
> > the evaluation of e, [...], would evaluate one of the following express=
ions:
> > [...]; a relational or equality operator where the result is unspecifie=
d;"
>=20
> I think the second quote refers to places in [expr.eq] that say "the resu=
lt
> is unspecified", not to all instances of unspecified behavior in the
> standard.

Doesn't [expr.eq] make it unspecified though?

[expr.eq]p6 says: "If two operands compare equal, the result is true for th=
e =3D=3D
operator and false for the !=3D operator. If two operands compare unequal, =
the
result is false for the =3D=3D operator and true for the !=3D operator. Oth=
erwise,
the result of each of the operators is unspecified."

If it is unspecified whether a subsequent string literal evaluation produces
the same object or a different object then it's unspecified whether the two
operands will or won't compare equal, so the result of the operators is also
unspecified.=