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Date:	Mon, 23 Jan 2012 12:13:55 -0800
From:	Colin D Bennett <colin AT gibibit DOT com>
To:	geda-help AT delorie DOT com
Subject:	Re: [geda-help] Help, how can I help?
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On Sun, 22 Jan 2012 15:43:06 -0800
Andrew Poelstra <asp11 AT sfu DOT ca> wrote:

> Function pointers may not be casted to function pointers of
> different types. (This is very irritating, but it's what the
> standard says.)

I don't see how it's irritating.  It's just the only sane thing to
do.  How is a function pointer usefull unless you know the argument
types?

> Calling a function with an invalid declaration is
> even worse, since it has the same effect without warning the
> compiler. For example, the author does the following:
> 
>   char *malloc();
>   char *s = malloc(BUFSIZ);
> 
> which tells the compiler that malloc() is a function declared as
> 
>   char *malloc (int);

Doesn't the empty argument list in the declaration of malloc()
mean the number and type of arguments is completely unspecified,
equivalent to:

    char *malloc(...);

and that means you could write the following code

    malloc("Hello", 3.54f);
    malloc();

> when in fact it is
> 
>   void *malloc(size_t);
> 
> This is not labelled a pitfall, but it is. If you want malloc,
> include <stdlib.h>. This will give you the correct signature.

A good practice is of course to never declare a function apart from
the “standard” supplied interface in its header.
Header file = interface.
Object file / C source file = implementation.

Regards,
Colin

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