Re: [Patch] CVS-Guile compilation problems

[Dirk Herrmann]

On 15 Feb 2001, Matthias Koeppe wrote:

> Marius Vollmer <address@hidden> writes:
> 
> > Would it suffice to just use this?
> > 
> >     next_symbol:
> >       ;
> >     }
> > 
> > "(void)0" looks strange.
> 
> I don't think that a singleton ";" is a C statement.  That's why one
> has to write `do { ... } while (0)' in all these preprocessor macros
> -- just to avoid a singleton ";".

I found the following in "N843, the official committee document" at
http://www.dkuug.dk/JTC1/SC22/WG14/www/docs/n843.htm. 

       [#3]  A  null  statement  (consisting  of  just a semicolon)
       performs no operations.

       [... example deleted]

       [#5] EXAMPLE 2 In the program fragment

               char *s;
               /* ... */
               while (*s++ != '\0')
                       ;

       a null statement is used to supply an empty loop body to the
       iteration statement.


       [#6] EXAMPLE 3 A null statement may also be used to carry  a
       label just before the closing } of a compound statement.

               while (loop1) {
                       /* ... */
                       while (loop2) {
                               /* ... */
                               if (want_out)
                                       goto end_loop1;
                               /* ... */
                       }
                       /* ... */
               end_loop1: ;
               }

Thus, using a ";" as a no-op statement should be alright (or has the
definition changed from the old C standard?).  Probably there are other
reasons why many macros use the "do {...} while (0)" wrapper?

Thus, except someone can prove that ";" is not allowed in the current C
standard, I would prefer the ";" solution over the "(void)0;"

Best regards,
Dirk Herrmann