egcs and pointers to methods / compatibility with gcc 2.7.2

egcs and pointers to methods / compatibility with gcc 2.7.2

[Rainer Dorsch]

I have a program, which compiles without warnings (-Wall) on gcc 2.7.2 and 
does not compile with egcs. Are there anywhere migration guidlines or a kind 
of checklist which things are incompatible now?

Does anybody know, how I can fix this problem?


I include my code, which uses pointers to class methods:

#include <iostream.h>

class testclass{
public:
  /** Default Constructor. */
  testclass(){}
  /** Destructor. */
  ~testclass(){}
  /** Add numbers. */
  int Add(int a, int b){return(Convert(testclass::add, a, b));}
  /** Sub numbers. */
  int Sub(int a, int b){return(Convert(testclass::sub, a, b));}
private:
  /** Debug support. */
  int debuglevel;
  /** Convert. */
  int Convert(int (testclass::*Operation)(int, int), int a, int b){
    // Do some standard computation ..., 

    // and call the Operation given as paramters
    return(Operation(a,b));
  }
  /** add. */
  int add(int a, int b){return(a+b);}
  /** sub. */
  int sub(int a, int b){return(a-b);}
}; /* class testclass */


main()
{
  testclass a;

  cout << a.Add(5,6) << endl;
}


The error messages are:

$ g++ -Wall test4.cc
test4.cc: In method `int testclass::Add(int, int)':
test4.cc:12: no matching function for call to `testclass::Convert (int (testclass::)(int, int), int &, int &)'
test4.cc:19: candidates are: testclass::Convert(int (testclass::*)(int, int), int, int)
test4.cc:12: warning: control reaches end of non-void function `testclass::Add(int, int)'
test4.cc: In method `int testclass::Sub(int, int)':
test4.cc:14: no matching function for call to `testclass::Convert (int (testclass::)(int, int), int &, int &)'
test4.cc:19: candidates are: testclass::Convert(int (testclass::*)(int, int), int, int)
test4.cc:14: warning: control reaches end of non-void function `testclass::Sub(int, int)'
test4.cc: In method `int testclass::Convert(int (testclass::*)(int, int), int, int)':
test4.cc:23: must use .* or ->* to call pointer-to-member function in `Operation (...)'
test4.cc:24: warning: control reaches end of non-void function `testclass::Convert(int (testclass::*)(int, int), int, int)'                    

I am using

$ g++ -v
Reading specs from /usr/lib/gcc-lib/i486-linux/egcs-2.90.28/specs
gcc version egcs-2.90.28 980423 (egcs-1.0.3 prerelease)       


Thank you.
-- 
Rainer Dorsch
Abt. Rechnerarchitektur  e-mail:rainer.dorsch@informatik.uni-stuttgart.de
Uni Stuttgart            Tel.: 0711-7816-215

Re: egcs and pointers to methods / compatibility with gcc 2.7.2

[Alexandre Oliva]

Rainer Dorsch <rainer@rainer.informatik.uni-stuttgart.de> writes:

> Does anybody know, how I can fix this problem?

In order to form a pointer to member, you must use the syntax

&foo::bar

(note the address-of operator) instead of just

foo::bar

Which gcc 2.7 used to accept.

-- 
Alexandre Oliva
mailto:oliva@dcc.unicamp.br mailto:aoliva@acm.org
http://www.dcc.unicamp.br/~oliva
Universidade Estadual de Campinas, SP, Brasil