[Bug c++/67113] New: unintelligent error message "only declarations of constructors can be 'explicit'" in cpp file's constructor define.

[Bug c++/67113] New: unintelligent error message "only declarations of constructors can be 'explicit'" in cpp file's constructor define.

[robinh3123 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67113

            Bug ID: 67113
           Summary: unintelligent error message "only declarations of
                    constructors can be 'explicit'" in cpp file's
                    constructor define.
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: robinh3123 at gmail dot com
  Target Milestone: ---

For the following codes (in 3 files):

$ cat a.cpp
#include "a.h"

int A::f()
{
        return n+1;
}

explicit A::A(int _n)   // <=== error at this line
{
        n = _n;
}



$ cat  a.h
class A
{
public:
        int n;
        int f();
        explicit A(int _n);
};



$ cat main.cpp
#include <iostream>
#include "a.h"  // for class A

using namespace std;

int main()
{
        A a(5);
        int i = a.f();
        cout << i << endl;
    return 0;
}


The compiler reports error message:
a.cpp:8:21: error: only declarations of constructors can be 'explicit'
 explicit A::A(int _n)

This is misleading, since A::A is really a constructor.
The error message should be something similar to:
     extra explicit before function A::A

[Bug c++/67113] unintelligent error message "only declarations of constructors can be 'explicit'" in cpp file's constructor define.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67113

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The diagnostic is technically correct (the best kind of correct!) because that
is a definition of a constructor, not just a declaration.

i.e. you are focusing on the word constructors and saying "but it is a
constructor!" when you should be focusing on "declarations of constructors".

[Bug c++/67113] unintelligent error message "only declarations of constructors can be 'explicit'" in cpp file's constructor define.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67113

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |5.0

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is already fixed anyway, gcc 5 says:

a.cc:5:15: error: ‘explicit’ outside class declaration
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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/67114] [MinGW64] build failure with POSIX threads enabled
Date: Tue, 04 Aug 2015 11:51:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg114

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-08-04
     Ever confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The problem is real, but obviously this patch is not acceptable because you
would need to add pthread_less to every implementation of pthreads, and to the
POSIX standard. GCC doesn't only support mingw.