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From: joemac@apple.UUCP (Joe MacDougald)
Newsgroups: comp.lang.c++
Subject: cfront/c++ problem
Message-ID: <6191@apple.UUCP>
Date: Wed, 9-Sep-87 21:13:25 EDT
Article-I.D.: apple.6191
Posted: Wed Sep  9 21:13:25 1987
Date-Received: Sat, 12-Sep-87 03:04:43 EDT
Organization: Apple Computer, Inc., Cupertino, USA
Lines: 39
Keywords: pointer to virtual method


cfront dies with an bus error when compiling the following:

struct T {
	int f;
		T() { f = 1; }	// constructor
	virtual int getf();
};

int T::getf()
{
	return f;
}

typedef int (T::*PROC)();	// S 5.4.5  p. 154 : pointer to member function
				// of T taking no args, returning int.
main()
{
	T t;			// t is an instance of T

	PROC p = &T::getf;	// p points to T's member function getf

/*ERROR*/ int r = (t.*p)();	// call function pointed at by p, assign to r
}

The error occurs at the point of invocation of the function pointed to by p.

If the member function is not declared virtual there are no problems in 
compilation or execution.

Nowhere does Stroustrup mention pointers to virtual methods, so I wonder if it
is a valid operation.  If it is invalid, cfront needs to exit more gracefully.

Has anyone used this aspect of the language?

Any comments would be greatly appreciated.
	
	Thanks,
		Joe