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

[Greg B. <ba...@cs...>]

Scott Lenser <sl...@cs...> writes:

> 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?

FUNC_NAME wouldn't properly expand to be the function name of the
location where the inline function was invoked, but would rather just
always name the inline function (not very useful for finding your errors!)

Thanks,
Greg


> 
> - 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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