c++/3662: Incorrect warnings with overridden virtual functions in template class

c++/3662: Incorrect warnings with overridden virtual functions in template class

[stuart]

>Number:         3662
>Category:       c++
>Synopsis:       Incorrect warnings with overridden virtual functions in template class
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jul 12 09:16:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     stuart@personalrobots.com
>Release:        gcc-3.0
>Organization:
>Environment:
Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0/specs
Configured with: ../gcc-3.0/configure --enable-threads
Thread model: posix
gcc version 3.0
>Description:
Compiling the attached file gives the following error:

test.cpp: In member function `TYPE CList<TYPE>::InvalidValue() [with TYPE = 
   int]':
test.cpp:11:   instantiated from `TYPE CList<TYPE>::RemoveHead() [with TYPE = int]'
test.cpp:39:   instantiated from here
test.cpp:14: warning: return to non-pointer type `int' from NULL
test.cpp:14: warning: argument to non-pointer type `int' from NULL

It seems to me that gcc is checking the wrong function and therefore emitting
an incorrect warning - stepping through the running program we never call
TYPE CList<TYPE>::InvalidValue(), only TYPE CTypeList<TYPE>::InvalidValue()
which is correct I believe.
>How-To-Repeat:
Compile the attached file with gcc-3.0
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: application/octet-stream; name="test.cc"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="test.cc"

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Cn0K

Re: c++/3662: Incorrect warnings with overridden virtual functions in template class

[gdr]

Synopsis: Incorrect warnings with overridden virtual functions in template class

Responsible-Changed-From-To: unassigned->gdr
Responsible-Changed-By: gdr
Responsible-Changed-When: Sun Aug 12 08:04:18 2001
Responsible-Changed-Why:
    See below.
State-Changed-From-To: open->closed
State-Changed-By: gdr
State-Changed-When: Sun Aug 12 08:04:18 2001
State-Changed-Why:
    Well, actually the issue is subtile.  In the instantiation
    of the base class CList<int>, GCC discovers the declaration of
    a virtual function and since every virtual function is used  even
    if it -appears- unused (a language definition requirement) GCC
    proceeds to check semantics restruictions, thus the warning.
    
    Arguably, GCC could use a type-based analysis to discover that 
    the base class function won't be used and suppress the warning
    but I guess that is a feature request.
    
    -- Gaby

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=3662&database=gcc