Re: c++/9437: template function parameter `T*' shouldn't match pointers to members

Re: c++/9437: template function parameter `T*' shouldn't match pointers to members

[nathan]

Synopsis: template function parameter `T*' shouldn't match pointers to members

Responsible-Changed-From-To: unassigned->nathan
Responsible-Changed-By: nathan
Responsible-Changed-When: Tue Jan 28 17:53:01 2003
Responsible-Changed-Why:
    mine

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9437

Re: c++/9437: template function parameter `T*' shouldn't match pointers to members

[nathan]

Synopsis: template function parameter `T*' shouldn't match pointers to members

State-Changed-From-To: analyzed->closed
State-Changed-By: nathan
State-Changed-When: Wed Jan 29 11:38:49 2003
State-Changed-Why:
    mainline and 3.3 branch
    2003-01-28  Nathan Sidwell  <nathan@codesourcery.com>
    
    	PR c++/9437
    	* pt.c (unify): Don't unify '*T' with 'U C::*'.
    
    2003-01-28  Nathan Sidwell  <nathan@codesourcery.com>
    
    	PR c++/9437
    	* g++.dg/template/unify4.C: New test.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9437

Re: c++/9437: template function parameter `T*' shouldn't match pointers to members

[bangerth]

Synopsis: template function parameter `T*' shouldn't match pointers to members

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Fri Jan 24 20:12:59 2003
State-Changed-Why:
    Something's indeed wrong here. To see what the template
    parameter matches, execute the following variation:
    -------------------------
    extern "C" void printf (const char *, ...);
    
    struct S {
        template <typename T>
        operator T* () const {
          printf ("%s\n", __PRETTY_FUNCTION__);
          return static_cast<T*> (0);
        }
    } null;
    
    struct A { int i; };
    
    static void f (int A::* pmi) { }
    
    int main () { f (null); }
    -----------------------------
    It displays
    g/a> /home/bangerth/bin/gcc-3.4-pre/bin/c++ x.cc
    g/a> ./a.out
    S::operator T*() const [with T = int A::*]
    
    But then the return type would be _pointer_ to member 
    pointer, not member pointer.
    
    Confirmed with 2.95, 3.2.2, 3.3, 3.4
    
    W.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9437

c++/9437: template function parameter `T*' shouldn't match pointers to members

[martin]

>Number:         9437
>Category:       c++
>Synopsis:       template function parameter `T*' shouldn't match pointers to members
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          accepts-illegal
>Submitter-Id:   net
>Arrival-Date:   Fri Jan 24 19:46:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Martin Buchholz
>Release:        g++ (GCC) 3.3 20030122 (prerelease)
>Organization:
>Environment:
Linux x86
>Description:
The source file below should fail to compile
with something like `no conversion to int A::*',
as it does with icc and Comeau C++.

The standard is not completely clear on this, but
here is a rationale for why accepting the code is wrong:

If `T*' matches `int A::*', then what type is T??
`int A::' is not a type, and T cannot be int, since 
the types `int *' and `int A::*' are very different.

A pointer to member is not a pointer.

Code:
----------------------------------------------------
struct
{
  template <typename T>
  operator T* () const { return static_cast<T*> (0); }
} null;

struct A { int i; };

static void f (int A::* pmi) { }

int main () { f (null); }
>How-To-Repeat:
Compile above code with `g++ null_ptr.c'.
It incorrectly compiles without warning or error.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: