mcf@trlamct.trl.oz.au (Michael Flower) (11/01/90)
I have what I suspect is a bug with the AT&T C++ compiler release 2.1.
The following piece of code demonstrates the problem.
With line 1 in class Object uncommented and line 2 commented out
the compiler objects correctly, that variable a in main() is an instance of
an abstract class, ie:
t.c", line 21: error: declaration of object of abstract class Object
1 error
(line 21 refers to the line "Object a;" in main()).
With line 2 in class object uncommented and line 1 commented out
the code compiles without error.
class Parsable {
public:
virtual void parse() = 0;
virtual void write_out() = 0;
};
class Object : public virtual Parsable {
public:
//virtual void draw() {}; /* 1 */
//void draw() {}; /* 2 */
};
main(){
Object a;
}
Using the g++ compiler Version 1.27, the compiler doesn't object to
either form of the program however the linker flags the two
undefined symbols created by the deferred functions parse() and write_out().
Is the AT&T compiler in error here or am I in error?
Shouldn't it complain about the declaration of a in both cases.
Shouldn't the g++ compiler complain of the declaration of an object
of an abstract class.
(perhaps it should and has been fixed in subsequent releases?).
What is the current GNU c++ release?
Needless to say, I had 'a' declared (supposedly) satisfactorily, until I made
some trivial change to class Object and I was told about my declaration
of an object of an abstract class.
Cheers ...mcf
Michael Flower
Artificial Intelligence Systems Email: flower@trl.oz.au
Telecom Research Laboratories Voice: +61 3 541 6179
Melbourne, AUSTRALIA Fax: +61 3 543 8863