[Bug c++/113110] GCC rejects call to more specialized const char array version with string literal

[harald at gigawatt dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113110

Harald van Dijk <harald at gigawatt dot nl> changed:

           What    |Removed                     |Added
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                 CC|                            |harald at gigawatt dot nl

--- Comment #6 from Harald van Dijk <harald at gigawatt dot nl> ---
(In reply to Jason Liam from comment #3)
> Are you sure? I mean if you add another template parameter `U` to the second
> parameter and use it then gcc starts accepting the code and using the more
> specialized version. Demo:https://godbolt.org/z/W7Ma6c5Ts

In order to determine whether int compare(const char (&)[N], const char (&)[M])
is more specialised than int compare(const T &, const T &), template argument
deduction is attempted to solve one in terms of the other. Solving gives T =
char[N] for the first parameter, but T = char[M] for the second parameter. This
is a conflict that is ignored by MSVC.

When adding the second template parameter `U`, solving gives T = char[N], and U
= char[M]. This is never a conflict, this unambiguously makes the array version
more specialised.

(In reply to Andrew Pinski from comment #5)
> I am still suspecting MSVC of not implementing the C++ Defect report 214 .

At first glance, both GCC/clang and MSVC behaviour look like legitimate but
different interpretations of DR 214. Whether MSVC is right to ignore that
conflict is an open question covered by
https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#2160.