c++/6523: bug with pointers to template functions

c++/6523: bug with pointers to template functions

[Oliver Schoenborn]

>Number:         6523
>Category:       c++
>Synopsis:       bug with pointers to template functions
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          ice-on-legal-code
>Submitter-Id:   net
>Arrival-Date:   Tue Apr 30 14:46:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Oliver Schoenborn
>Release:        3.0.1
>Organization:
>Environment:
System: IRIX64 onyx1 6.5 07091542 IP27
host: mips-sgi-irix6.5
build: mips-sgi-irix6.5
target: mips-sgi-irix6.5
configured with: ../configure --prefix=/usr/freeware --enable-version-specific-runtime-libs --disable-shared --enable-threads --enable-haifa
>Description:
Note that I built g++ 3.0.4 on my home linux system (Mandrake 8.1) 
and got same compiler failure so it is unlikely to be related to environment. 
Output from g++ is following:
     funcPtrProblem.cc: In function `int main()':
     funcPtrProblem.cc:32: Internal compiler error in 
         c_expand_expr, at c-common.c: 4121

A class Tester defines a function pointer typedef BarFunc and an example static function 
template of that type, called bar<T>(). Two different class templates Foo1<T> and Foo2<T> 
each have a /templated/ constructor (ie Foo1<T>::Foo1<T2>) that use a pointer to the 
bar<T2>() template function.  One Foo accesses this bar<T> via inheritence, i.e. Foo2 inherits 
from Tester.  The other, Foo1, accesses it directly since it is static and public.  In other words, 
both Foo classes do exactly the same thing (semantically) but in different ways.  Foo2 causes 
compiler crash. Compilation works if constructor of Foo2 is not templated, or even if it is but 
Foo2 itself is not a class template, or if bar is not a template.

>How-To-Repeat:
Put following code in one file called funcPtrProblem.cc and do 
g++ -c funcPtrProblem.cc
to get the above internal compiler error

struct Tester
{
    typedef void (*BarFunc)();

    template <typename T>
    static void bar() {}
};

template <typename T>
struct Foo1
{
    template <typename T2>
    Foo1(T2*, Tester::BarFunc = &Tester::bar<T2>) {}
};

template <typename T>
struct Foo2: private Tester
{
    template <typename T2>
    Foo2(T2*, BarFunc = &bar<T2>) {}
};

int main()
{
     Foo1<int> foo1(new int);
     Foo2<int> foo2(new int);
}

>Fix:
Do not use inheritence. This means that Tester must have everything public 

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

Re: c++/6523: bug with pointers to template functions

[Oliver Schoenborn]

The following reply was made to PR c++/6523; it has been noted by GNATS.

From: Oliver Schoenborn <oliver.schoenborn@utoronto.ca>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org,
 	reichelt@igpm.rwth-aachen.de, gcc-bugs@gcc.gnu.org,
 	nobody@gcc.gnu.org
Cc:  
Subject: Re: c++/6523: bug with pointers to template functions
Date: Mon, 27 May 2002 21:34:50 -0400

 > From: Reichelt <reichelt@igpm.rwth-aachen.de>
 > To: gcc-gnats@gcc.gnu.org, oliver.schoenborn@utoronto.ca, gcc-bugs@gcc.gnu.org,
 >         nobody@gcc.gnu.org
 > Subject: Re: c++/6523: bug with pointers to template functions
 > Date: Mon, 27 May 2002 16:49:49 +0200
 > 
 >  Hi,
 > 
 >  the example can be reduced to the one in PR 4249.
 >  Therefore, the PR can probably be closed.
 > 
 >  Greetings,
 >  Volker Reichelt
 > 
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6523
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=4249
 
 It's not clear to me that 6523 can be reduced to 4249, unless someone
 knows what *causes* the bug. Indeed, my example Foo1 class (see bug
 report 6523 abnove) is similar to 4249 example, IT actually compiles
 fine, it is the *Foo2* class example that causes compiler to crash on
 the g++ source file. That one does NOT reduce to 4249 (AFAICT). So it
 may well be a different bug. I would rather not close 6523 but just add
 a note in 4249 that the bugs may be related, unless someone knows for
 sure that they are the same (rather than just appear related).
 
 Oliver

Re: c++/6523: bug with pointers to template functions

[Reichelt]

The following reply was made to PR c++/6523; it has been noted by GNATS.

From: Reichelt <reichelt@igpm.rwth-aachen.de>
To: gcc-gnats@gcc.gnu.org, oliver.schoenborn@utoronto.ca, gcc-bugs@gcc.gnu.org,
        nobody@gcc.gnu.org
Cc:  
Subject: Re: c++/6523: bug with pointers to template functions
Date: Mon, 27 May 2002 16:49:49 +0200

 Hi,
 
 the example can be reduced to the one in PR 4249.
 Therefore, the PR can probably be closed.
 
 Greetings,
 Volker Reichelt
 
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6523
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=4249
 
 

Re: c++/6523: bug with pointers to template functions

[lerdsuwa]

Synopsis: bug with pointers to template functions

State-Changed-From-To: open->analyzed
State-Changed-By: lerdsuwa
State-Changed-When: Wed May 15 06:43:19 2002
State-Changed-Why:
    Confirmed.  Still present in 3.1 branch and main trunk.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6523