[Bug c++/67026] New: GCC incorrectly rejects well-formed constexpr function definition

[Bug c++/67026] New: GCC incorrectly rejects well-formed constexpr function definition

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67026

            Bug ID: 67026
           Summary: GCC incorrectly rejects well-formed constexpr function
                    definition
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anders.granlund.0 at gmail dot com
  Target Milestone: ---

Consider the following program (proc.cc):

void g() {}
constexpr void f() { return; g(); }
int main() {}

Compile it with the following command line:

g++ prog.cc -std=c++14 -pedantic-errors

The following error message is given:

prog.cc: In function 'constexpr void f()':
prog.cc:2:31: error: call to non-constexpr function 'void g()'
 constexpr void f() { return; g(); }
                               ^
I expected to get no error message since the program is well-formed.

I have tried this with gcc HEAD 6.0.0 20150726 here:

http://melpon.org/wandbox/permlink/Hd5t7ppNQWFqioUx

For comparison clang accepts the program with no error messages.

[Bug c++/67026] GCC incorrectly rejects well-formed constexpr function definition

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67026

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC does not implement the full C++14 rules for constexpr yet.  That is having
a return type of void is not implemented yet.  It was invalid for C++11 to have
a constexpr with void.

[Bug c++/67026] GCC incorrectly rejects well-formed constexpr function definition

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67026

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Actually wait.  I think this is invalid and clang is incorrect in not rejecting
it.  Because you have a call to a non constexpr in a constexpr function; does
not matter if it is after a return or not.

[Bug c++/67026] GCC incorrectly rejects well-formed constexpr function definition

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67026

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-08-29
                 CC|                            |trippels at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #4 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Confirmed. 

Another example:

constexpr int f3() {
  return 0;
  throw;
}

Checking should stop after the return statement.