[Bug c++/102097] New: Error in selecting more specialized function in case of ambiguity

[Bug c++/102097] New: Error in selecting more specialized function in case of ambiguity

[fchelnokov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102097

            Bug ID: 102097
           Summary: Error in selecting more specialized function in case
                    of ambiguity
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

In this program
```
void fun(auto&){}
void fun(auto&&){}
int main() { void(*ptr)(int&) = &fun; }
```
GCC reports ambiguity of function selection. Clang reports the same error as
well. But the community of stack-overflow believes
(https://stackoverflow.com/questions/68949303/which-is-the-most-specialized-function-template-in-the-context-of-taking-the-add)
that it is not correct compiler behavior and a more specialized function
`fun(auto&)` must be selected.

[Bug c++/102097] Error in selecting more specialized function in case of ambiguity

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102097

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-08-27

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is a C++11 version of the same problem:
template<class T>
void fun(T&){}
template<class T>
void fun(T&&){}
int main() { void(*ptr)(int&) = &fun; }

ICC accepts this one.

MSVC accepts both the original and this C++ version.