Re: c++/3671: g++ incorrectly tries to instantiate multiple member template specializations

Re: c++/3671: g++ incorrectly tries to instantiate multiple member template specializations

[Wolfgang Bangerth]

The following reply was made to PR c++/3671; it has been noted by GNATS.

From: Wolfgang Bangerth <bangerth@ticam.utexas.edu>
To: gcc-gnats@gcc.gnu.org, <gcc-bugs@gcc.gnu.org>
Cc:  
Subject: Re: c++/3671: g++ incorrectly tries to instantiate multiple member
 template specializations
Date: Fri, 15 Nov 2002 20:25:42 -0600 (CST)

 Good question what happens here:
 ----------------------------------
 enum T1 {a};
 enum T2 {b};
 
 struct Y {
   template <T1 i> void foo();
   template <T2 i> void foo();
 };
 
 template void Y::foo<a> ();
 
 // int main() {
 //   Y c;
 //   c.foo<a>();
 // }
 ---------------------------------
 I get
 tmp/g> /home/bangerth/bin/gcc-3.3x-pre/bin/c++ x.cc
 x.cc:9: error: cannot convert `T1' to `T2' in initialization
 x.cc:9: error: non-constant `<expression error>' cannot be used as template
    argument
 x.cc: In instantiation of `void Y::foo() [with T1 i = a]':
 x.cc:9:   instantiated from here
 x.cc:9: error: explicit instantiation of `void Y::foo() [with T1 i = a]' 
 but no
    definition available
 
 
 If I use the commented main function instead of the explicit 
 instantiation, I get
 tmp/g> /home/bangerth/bin/gcc-3.3x-pre/bin/c++ x.cc
 x.cc: In function `int main()':
 x.cc:13: error: cannot convert `T1' to `T2' in initialization
 x.cc:13: error: non-constant `<expression error>' cannot be used as template
    argument
 
 which I find even less helpful.
 
 Regards
   Wolfgang
 
 -------------------------------------------------------------------------
 Wolfgang Bangerth              email:           bangerth@ticam.utexas.edu
                                www: http://www.ticam.utexas.edu/~bangerth
 
 

Re: c++/3671: g++ incorrectly tries to instantiate multiple member template specializations

[lerdsuwa]

Synopsis: g++ incorrectly tries to instantiate multiple member template specializations

State-Changed-From-To: open->analyzed
State-Changed-By: lerdsuwa
State-Changed-When: Fri Jun  7 07:47:49 2002
State-Changed-Why:
    Confirmed.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=3671

c++/3671: g++ incorrectly tries to instantiate multiple member template specializations

[weissr]

>Number:         3671
>Category:       c++
>Synopsis:       g++ incorrectly tries to instantiate multiple member template specializations
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 13 03:26:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Roland Weiss
>Release:        gcc version 3.0
>Organization:
>Environment:
i686-pc-linux-gnu, Linux Mandrake 8.0
>Description:
g++ emits the following error message when compiling my test program:

Dependent_Types_Specialization.cpp: In function `int main()':
Dependent_Types_Specialization.cpp:79: cannot convert `Index2' to `Index1' in
   initialization
Dependent_Types_Specialization.cpp:79: non-constant `<expression error>' cannot
   be used as template argument

The problems seems to be that g++ incorrectly tries to instantiate both versions of the get_index member template in the class template Compound_Type. Therefore the index_type given at the instantiation place in the main program will not match one version and trigger the error message.

The program compiles without problems using the EGD frontend 2.44.
>How-To-Repeat:
run g++ on the file Dependent_Types_Specialization.cpp, no special flags are needed
>Fix:
don't know one!
>Release-Note:
>Audit-Trail:
>Unformatted:
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