[Bug c++/101982] New: function parameter should not accept auto as placeholder-type-specifier

[Bug c++/101982] New: function parameter should not accept auto as placeholder-type-specifier

[nickhuang99 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101982

            Bug ID: 101982
           Summary: function parameter should not accept auto as
                    placeholder-type-specifier
           Product: gcc
           Version: 7.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nickhuang99 at hotmail dot com
  Target Milestone: ---

GCC7.5 accepts *auto* as placeholder-type-specifier without error or warning.
Considering following code snippet is legal only with -std=c++20:

   void f(auto i){} 

GCC8.x and later gives warning which is at least not incorrect. As a contrast,
both clang (https://www.godbolt.org/z/9x6E5xrne) and
MSVC(https://www.godbolt.org/z/3hWPsrcqz) considers it is illegal without
-std=c++20 option which is compliant with spec: 

   warning: use of ‘auto’ in parameter declaration only available with
‘-fconcepts-ts’

[Bug c++/101982] [7.5]function parameter should not accept auto as placeholder-type-specifier

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101982

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is a GCC extension and accepted by design.

GCC 7 has been unsupported for more than two years, so bugs that only affect
7.x and not newer versions are not going to get fixed.

[Bug c++/101982] [7.5]function parameter should not accept auto as placeholder-type-specifier

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101982

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #1)
> GCC 7 has been unsupported for more than two years,

Actually slightly less than two years (since November 2019). But it's still
unsupported.

[Bug c++/101982] [7.5]function parameter should not accept auto as placeholder-type-specifier

[nickhuang99 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101982

--- Comment #3 from qingzhe huang <nickhuang99 at hotmail dot com> ---
Thank you for clarifications!