Xref: utzoo comp.lang.c++:7801 gnu.g++:864
Path: utzoo!utgpu!watserv1!watmath!uunet!samsung!sol.ctr.columbia.edu!emory!hubcap!rajarar
From: rajarar@hubcap.clemson.edu (Bala Rajaraman)
Newsgroups: comp.lang.c++,gnu.g++
Subject: Question re. Pointers to functions (Passed Parameters are Garbage)
Keywords: Pointers to functions/members, Garbage Parameters
Message-ID: <9140@hubcap.clemson.edu>
Date: 28 May 90 21:56:30 GMT
Distribution: na
Organization: Clemson University, Clemson, SC
Lines: 66


Hi,
	I have a question regarding pointers to functions and a weird
problem I am facing.
	I need to call a function (which could either be a global
function or a member function of a class). I store a pointer to this
function in a private variable in the class. I look at two cases for the
initialization of this private variable,
	1. A global function
	2. A member function of the same class
In both cases, the functions have an int parameter. However, when I
print this int value, I get a correct answer if the function is global
but garbage if the function pointer is that of a member function.
	I have enclosed a minimal program where this seems to occur.
This also occurs in a broader context. The life of a simulation hinges
on this. So,
	HELP!! HELP!! HELP!! HELP!! HELP!!
This is rather urgent and I have really tried a lot of variations to
crack this puzzle.
	THANKS,

Bala Rajaraman

----------------------------  CUT HERE  ------------------------------

#include <stream.h>

typedef int (*intfn)(int);

class y {
	intfn myfn;
public:
	abc() { myfn = intfn(def); (*myfn)(2); }
	abc(intfn a) { myfn = a; (*myfn)(2); }

	def(int a) { cout << "DEF: " << a << "\n"; }
	};

fin(int a)

{
cout << "FIN: " << a << "\n";
}

main()

{
y ysp;

ysp.abc(fin);
ysp.abc();

intfn d = intfn(&y::def);
ysp.abc(d);
}

--------------------------------------------------------------------------

COMPILATION and RESULT:

bengal[32%] g++ -o x x.c
bengal[33%] x
FIN: 2
DEF: 8848
DEF: 8848
bengal[34%]