[Bug c++/86369] constexpr const char* comparison fails

["aaron at aaronballman dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86369

Aaron Ballman <aaron at aaronballman dot com> changed:

           What    |Removed                     |Added
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                 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.
> > 
> > [lex.string]p16 says: "whether successive evaluations of a string-literal
> > yield the same or a different object is unspecified."
> > 
> > [expr.const]p2 says: "An expression e is a core constant expression unless
> > the evaluation of e, [...], would evaluate one of the following expressions:
> > [...]; a relational or equality operator where the result is unspecified;"
> 
> I think the second quote refers to places in [expr.eq] that say "the result
> 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 the ==
operator and false for the != operator. If two operands compare unequal, the
result is false for the == operator and true for the != operator. Otherwise,
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.