🚀 go-pugleaf

In article <MATT.95Sep24001959@Austern>, clamage@Eng.Sun.COM (Steve Clamage) writes:
|>
|> jhg@mpd.tandem.com (Jim Garrison) writes:
|>
|> >The ARM states that it is illegal to declare a function in a
|> >derived class that differs from a virtual in a parent class by
|> >only its return type.  I.e.
|>
|> >class A
|> >{
|> >        virtual int foo();
|> >}
|>
|> >class B1 : public A
|> >{
|> >        char * foo(); // Illegal
|> >}
|>
|>
|> >Has the standard changed with respect to this?  IBM VisualAge C++
|> >now allows this (it's an EXTREMELY useful thing to be able to do),
|> >but the SGI compiler on which I'm working doesn't.
|>
|> The draft standard allows "covariant return types".
|>
|> If the base-class version of a virtual function returns a
|> pointer (or reference) to a class, the derived-class version may
|> return a pointer (or reference) to a class derived from the
|> original.
|>
|> Your example above is not allowed, because char* is not derived
|> from int. If the IBM compiler allows it, that would be a
|> non-standard extension.

  IBM's C++ compiler for AIX version 3.1.32 does not allow this
code to compile.  Just in case, I'll pass it along to the compiler
group as a possible bug.


--
John.

John J. Barton        jjb@watson.ibm.com            (914)784-6645
	<http://www.research.ibm.com/xw-SoftwareTechnology>
H1-C13 IBM Watson Research Center P.O. Box 704 Hawthorne NY 10598
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