c++/868: Macro && template class && member argument == ICE

[sadowski at lucent dot com]

>Number:         868
>Category:       c++
>Synopsis:       Macro && template class && member argument == ICE
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Nov 22 08:36:00 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     Gilles Sadowski
>Release:        gcc version 2.95.1 19990816 (release)
>Organization:
>Environment:
Reading specs from /opt/exp/gnu/lib/gcc-lib/sparc-sun-solaris2.4/2.95.1/specs
gcc version 2.95.1 19990816 (release)
SunOS 5.6 Generic_105181-14 sun4u sparc SUNW,Ultra-5_10
>Description:
Using a macro whose argument is a class member in the 
definition of a method of a template class provokes 
an internal compiler error.

Compiler output:
b.cc: In method `void Test<T>::make_test(T)':
b.cc:94: Internal compiler error.
b.cc:94: Please submit a full bug report.
b.cc:94: See <URL:http://www.gnu.org/software/gcc/faq.html#bugreport> for instructions.

In the code below, when BUG is defined, the compilation 
generates ICE (1) at the line where the 'SAVE' macro is 
used.  Nevertheless, similar code when used in a non 
template class (3) or whenever the macro argument is not 
a class member (2) compiles OK.

See attached file 'b.cc' for the macro definition.

///// A template class /////
template<typename T>
class Test
{
public:
  Test( T t ) : _t( t ) {}

  void make_test( T a ) {
    cerr << "Template:" << endl ;
    cerr << "_t=" << _t << endl ;

    if (1) {

#ifdef BUG
      SAVE( _t )	// ICE here (1)
      _t = a ;
#endif
      cerr << "_t=" << _t << endl ;
    }

    cerr << "_t=" << _t << endl ;
    return ;
  }

  void make_test_temp( T a ) {
    cerr << "Template (temporary):" << endl ;
    T b = _t ;
    cerr << "b=" << b << endl ;

    if (1) {

      SAVE( b )		// But NOT here (2)
      b = a ;
      cerr << "b=" << b << endl ;
    }

    cerr << "b=" << b << endl ;
    return ;
  }

private:
  T _t ;
} ;

///// NOT a template class /////
class Test_2
{
public:
  Test_2( string t ) : _t( t ) {}

  void make_test( string a ) {
    cerr << "No template:" << endl ;
    cerr << "_t=" << _t << endl ;

    if (1) {

      SAVE( _t )	// And also NOT here (3)
      _t = a ;
      cerr << "_t=" << _t << endl ;
    }

    cerr << "_t=" << _t << endl ;
    return ;
  }

private:
  string _t ;
} ;


int main()
{
  Test<string> t( "Hi" ) ;
  Test_2 t_2( "Hi_2" ) ;

  t.make_test( "Hello" ) ;
  t.make_test_temp( "Hello_temp" ) ;

  t_2.make_test( "Hello_2" ) ;

  return 0 ;
}
>How-To-Repeat:
This succeeds:
g++ --save-temps -o b b.cc

And the output of program 'b' should be:
Template:
_t=Hi
_t=Hi
_t=Hi
Template (temporary):
b=Hi
b=Hello_temp
b=Hi
No template:
_t=Hi_2
_t=Hello_2
_t=Hi_2


But this fails:
g++ --save-temps -o b -DBUG b.cc
>Fix:

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