[Bug c++/13452] New: No error on invalid (I think) C++ code

[Bug c++/13452] New: No error on invalid (I think) C++ code

[ian at airs dot com]

This code is compiled without error in the current mainline:

class C { public: template<typename i> int (*f())() const; };

However, it now seems to me that there should be an error on the trailing const.
 Otherwise, I have no idea what the trailing const means.  It appears that
generating a const method (i.e., a method for which `this' is a pointer to
const) requires

class C { public: template<typename i> int (*f() const)(); };

This may be a misunderstanding on my part, but at least some people share my
misunderstanding; see PR c++/13447.

-- 
           Summary: No error on invalid (I think) C++ code
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ian at airs dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13452

[Bug c++/13452] No error on invalid (I think) C++ code

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-23 18:22 -------
Confirmed but not a regression.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-12-23 18:22:24
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13452

[Bug c++/13452] No error on invalid (I think) C++ code

[Rainer dot Bensch at rsd dot rohde-schwarz dot com]

------- Additional Comments From Rainer dot Bensch at rsd dot rohde-schwarz dot com  2004-01-12 16:10 -------
(In reply to comment #0)
> However, it now seems to me that there should be an error on the trailing 
const.

No.

>  Otherwise, I have no idea what the trailing const means.  It appears that
> generating a const method (i.e., a method for which `this' is a pointer to
> const) requires
> class C { public: template<typename i> int (*f() const)(); };
> This may be a misunderstanding on my part, but at least some people share my
> misunderstanding; see PR c++/13447.

You declared a non const member function f() which returns a pointer to a const
member function. If the const is inside the parenteses, you declare a const 
member function f() which returns a pointer to a non const member function. 
Now, consider to place const at both...

Cheers, Rainer


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13452

[Bug c++/13452] No error on invalid (I think) C++ code

[ian at airs dot com]

------- Additional Comments From ian at airs dot com  2004-01-12 16:27 -------
Subject: Re:  No error on invalid (I think) C++ code

"Rainer dot Bensch at rsd dot rohde-schwarz dot com" <gcc-bugzilla@gcc.gnu.org> writes:

> You declared a non const member function f() which returns a pointer to a const
> member function. If the const is inside the parenteses, you declare a const 
> member function f() which returns a pointer to a non const member function. 
> Now, consider to place const at both...

I don't agree.  The function f() does not return a pointer to any sort
of member function.  It returns a simple pointer to function.

Consider this test case:

extern int bar();
class C { public: int (*f())() const; };
int (*C::f())() const { return bar; }

Right now this compiles without error.  But the `const' in the
declaration of C::f() is meaningless.  C::f() returns an ordinary
function.  I certainly can't declare `extern int bar() const'.

Conversely, this test case:

class C { public: int (*f())() const; int bar(); };
int (*C::f())() const { return C::bar; }

fails, with:

foo3.cc:2: error: argument of type `int (C::)()' does not match `int (*)()

Similarly, this one:

class C { public: int (*f())() const; int bar() const; };
int (*C::f())() const { return C::bar; }

fails with:

foo3.cc:2: error: argument of type `int (C::)() const' does not match `int (*)()'

(both these error messages are mildly bogus, since the case here is
not an argument mismatch, but a return mismatch, but that is a
separate issue).

So I still think that the trailing const is meaningless, and should
cause an error.

Ian


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13452

[Bug c++/13452] No error on invalid (I think) C++ code

[ian at airs dot com]

------- Additional Comments From ian at airs dot com  2005-05-25 00:33 -------
Just a note that this still fails to issue an error on mainline.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2003-12-23 18:22:24         |2005-05-25 00:33:19
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13452