[Bug c++/46831] New: Crash when it tries to do an invalid ICS with a conversion function template

[Bug c++/46831] New: Crash when it tries to do an invalid ICS with a conversion function template

[schaub-johannes at web dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

           Summary: Crash when it tries to do an invalid ICS with a
                    conversion function template
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: schaub-johannes@web.de


GCC crashes on this

struct B { }; 
struct D : B { }; 

struct A { 
  // [C++0x] default template argument for function template
  template<typename T = void> 
  operator D&(); 
}; 

void f(B&);

int main() {
  f(A());
}

This code clearly ill-formed by 13.3.3.1.2[over.ics.user] paragraph 3 . C.f.
13.3.3.1.4[ocer.ics.ref] paragraph 1.

[Bug c++/46831] [C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[schaub.johannes at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

--- Comment #1 from Johannes Schaub <schaub.johannes at googlemail dot com> 2010-12-07 04:09:25 UTC ---
-------------------------------------------------
GCC also rejects this valid code:
----------

struct A { 
  template<typename T = void> operator short(); 
  template<typename T = void> operator long(); 
}; 

void f(long); 
void f(int);

// this call is not ambiguous, but GCC claims it is
int main() { f(A()); }

Also, if we make the second conversion functon a non-template, GCC suddenly
accepts the code (right at it, the code is still valid). 

But that indicates that GCC has internally the handling of
13.3.3[over.match.best]p1 bullet 4 and bullet 5 reversed: It first checks
whether one is a template and the other is a non-template, and only then checks
whether the return type of F1 converts better than the return type of F2. 

--------------------------------------------------
We can make this to crash on valid code, too:
--------

struct B { }; 
struct D : B { }; 
struct A { 
  template<typename T = void> operator D&(); 
  operator long(); 
}; 

void f(long); 
void f(B&);

int main() { f(A()); }

[Bug c++/46831] [C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2010-12-07 10:59:16 UTC ---
Let's add Jason in CC.

[Bug c++/46831] [C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-12-07 11:22:40 UTC ---
Would be nice to have separate bugs for the separate issues ... otherwise
categorizing this is difficult.

[Bug c++/46831] [C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-12-07 15:37:04 UTC ---
The ICEs in the first and third examples are regressions against 4.5

[Bug c++/46831] [4.6 Regression][C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
   Target Milestone|---                         |4.6.0

[Bug c++/46831] [4.6 Regression][C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/46831] [4.6 Regression][C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.01.27 13:07:21
     Ever Confirmed|0                           |1

--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> 2011-01-27 13:07:21 UTC ---
(In reply to comment #0)
> GCC crashes on this
> 
> struct B { }; 
> struct D : B { }; 
> 
> struct A { 
>   // [C++0x] default template argument for function template
>   template<typename T = void> 
>   operator D&(); 
> }; 
> 
> void f(B&);
> 
> int main() {
>   f(A());
> }
> 
> This code clearly ill-formed by 13.3.3.1.2[over.ics.user] paragraph 3 . C.f.
> 13.3.3.1.4[ocer.ics.ref] paragraph 1.

This ICE is caused by revision 159335:

http://gcc.gnu.org/ml/gcc-cvs/2010-05/msg00387.html

[Bug c++/46831] [4.6 Regression][C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> 2011-01-27 13:09:52 UTC ---
(In reply to comment #1)
> 
> --------------------------------------------------
> We can make this to crash on valid code, too:
> --------
> 
> struct B { }; 
> struct D : B { }; 
> struct A { 
>   template<typename T = void> operator D&(); 
>   operator long(); 
> }; 
> 
> void f(long); 
> void f(B&);
> 
> int main() { f(A()); }

This ICE is also caused by revision 159335:

http://gcc.gnu.org/ml/gcc-cvs/2010-05/msg00387.html

[Bug c++/46831] [4.6 Regression][C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2011-02-20 23:26:03 UTC ---
Got it.

[Bug c++/46831] [4.6 Regression][C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> 2011-02-21 01:50:44 UTC ---
Author: jason
Date: Mon Feb 21 01:50:39 2011
New Revision: 170354

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=170354
Log:
    PR c++/46831
    * call.c (convert_class_to_reference): Don't try to set up a
    second conv sequence for non-viable candidates.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg2.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/46831] [4.6 Regression][C++0x] Crash when it tries to do an invalid ICS with a conversion function template

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46831

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-02-21 17:20:53 UTC ---
Fixed.