From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Passing functions as a parameter in C++
Date:	30 May 2000 10:41:55 GMT
Organization:	Aachen University of Technology (RWTH)
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Raul Carolus <carolura AT luther DOT edu> wrote:
> Ok, i'm about to blow my computer up over this problem.

> I have a nice little function:
> void TimerUpdate() { GlobalTime++; }
> all set up to hook to a timer.  I'm using Allegro and the MIDAS sound
> library in my
> project.  Since Midas doesn't like to work with Allegro's timer functions,
> i'm using one of midas's:
> MIDASsetTimerCallback(int, bool, void*, void*, void*);

> The three void*'s are functions.  

Thats extremely bad programming style on the side of MIDAS. Even in C,
you are not allowed to call a function through a pointer that has been
casted to 'void *', before it's used. You invoke undefined behaviour
that way. C++, because of its polymorphism support and its
consequences, is even stricter than C, here.

> So, my problem is, I really would like to use this, but it seems to not like
> C++ very much.  Can someone aid me in resolving my problem?

Have you checked whether the MIDAS prototype for
MIDASSetTimerCallback() is contained in an 'extern "C" { }' block? If
it isn't, you should add one.


-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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