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Path: utzoo!mnetor!seismo!think!ima!haddock!karl
From: karl@haddock
Newsgroups: net.lang.c++
Subject: Re: C++ problems with DMD code
Message-ID: <165200004@haddock>
Date: Mon, 22-Sep-86 11:04:00 EDT
Article-I.D.: haddock.165200004
Posted: Mon Sep 22 11:04:00 1986
Date-Received: Mon, 22-Sep-86 21:39:05 EDT
References: <66700003@uiucdcsp>
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Nf-ID: #R:uiucdcsp:66700003:haddock:165200004:000:1202
Nf-From: haddock!karl    Sep 22 11:04:00 1986


gaulke@uiucdcsp.CS.UIUC.EDU (Dave Gaulke) writes:
>I have found a problem with C++ when using it to write code for the DMD.
>The following is part of the output of the preprocessor when including the
>file <blit.h> for a simple program.
>
>typedef int (*ptr_fint)();
>main() { (*((int (*)())((ptr_fint *)0x0071d700)[ 43]))( 1 ); }

The problem is that "int (*)()" in oldC means "pointer to function returning
int" whereas in C++ it means "pointer to function taking no arguments and
returning int".  "typedef int (*ptr_fint)(...);" is the correct declaration
in C++, and presumably there's a macro somewhere in blit.h that uses the
oldC cast "(int (*)())" which should be "(int (*)(...))" in C++.

The other compatibility problem which came up recently was a collision
between a structure tag and a variable (which share one namespace in C++).

Bjarne: is there a CC option that gives you compatibility with oldC in these
two cases?  Also, ANSI C preserves the oldC meaning of "int (*)()" and adds
"int (*)(void)" for functions with no arguments.  Will C++ switch to this
notation?  Does it currently accept this notation?

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint