Re: [Scwm-devs] Re: question about VALIDATE macros

[Scott L. <sl...@cs...>]

Ah, I see.  And the do .. while(0) part is so that stuff like

if(a)
  DO_STUFF(1);
else
  DO_STUFF(2);

works as expected.  Is there a reason they aren't inline functions?

- Scott

> So that they work as you'd expect when preceded by an if clause-- they
> need to be a single statement (which many of them happen to already be,
> but if the macro definition got any more complicated, they wouldn't
> be).  E.g., consider:
> 
> #define DO_STUFF(x) \
>    do something;
>    do something else;
> 
> being used as:
> 
> if (...) 
>   DO_STUFF(x)
> 
> it'll expand into:
> 
> if (...)
> {
>   do something;
> }
> do something else;
> 
> I've added braces to stress the problem.  The do/while(0) makes it work
> as the user of the macro probably expected, w/o requiring her to
> remember to use braces everytime she uses DO_STUFF.
> 
> I think the GNU C programming standards mention this coding style, but I
> don't have a reference handy.
> 
> Thanks,
> Greg
> 
> 
> Scott Lenser <sl...@cs...> writes:
> 
> > Greg,
> > 
> > In the validate macros such as:
> > 
> > #define VALIDATE_WIN_USE_CONTEXT(win) \
> >   do { if ((win = ensure_valid(win,1,FUNC_NAME, SCM_BOOL_T, SCM_BOOL_F)) == 
> > SCM_BOOL_F) \
> >           return SCM_BOOL_F; } while (0)
> > 
> > Why do they all have a do { } while(0) around the code?
> > 
> > Thanks.
> > 
> > - Scott
> 
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