Re: [PLUG] C question: struct pointer error

[Will Dyson <will_dyson@pobox.com>]

Jeff Abrahamson wrote:
> > >    int foo(struct bar *b);
> > >
> > >    typedef struct bar {
> > > 	    int a;
> > >    } Bar;
> > >
> > >    foo(Bar *b)
> > >    {
> > > 	    return 0;
> > >    }

> My read of K&R is that, as long as you don't need to know the size of
> the struct pointer, you don't need to have the definition of the
> struct available in the current translation unit.
>
> The real issue here, since I could just #include bar.h, is that I
> don't want to #include extraneous files. It slows compilations, risks
> breaking data abstraction, and risks creating circular dependencies.

What you need is a forward declaration of struct bar; You are correct that 
 it does not need the definition, but it must know that struct bar is 
declared.

    struct bar; // forward declaration of struct bar

    int foo(struct bar *b);

    struct bar {
	    int a;
    };

    int foo(struct bar *b)
    {
	    return 0;
    }


--
Will Dyson
"Back off man, I'm a scientist!" -Dr. Peter Venkman

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