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Re: [Libvir] [PATCH] Check calls to printf-like functions (and some fixes)



On Mon, Mar 12, 2007 at 05:32:38PM +0000, Richard W.M. Jones wrote:
> Daniel P. Berrange wrote:
> >On Mon, Mar 12, 2007 at 05:16:52PM +0000, Richard W.M. Jones wrote:
> >>* Fix qemudDebug when debug not enabled
> >
> >Its not clear what was broken about the existing code ?
> >
> >This chunk:
> >
> >> #ifdef ENABLE_DEBUG
> >> #define qemudDebug(...) qemudLog(QEMUD_DEBUG, __VA_ARGS__)
> >> #else
> >>-#define qemudDebug(fmt, ...) do { } while(0);
> >>+#define qemudDebug(fmt, ...)
> >> #endif
> >
> >Will break / silently change code semantics, if qemudDebug is used in
> >situations like
> >
> >
> >   if (foo)
> >     qemudDebug("blah")
> >   wizz()
> 
> I mean this code _looks_ incorrect even if it actually isn't because of 
> the extra ';' in the macro.

The extra ; in the macro definition is bogus. I did actually mean to 
show

   if (foo)
      qemudDebug("blah");

Which would then turn into

   if (foo)
      ;

Which causes GCC to complain with

  cc1: warnings being treated as errors
  driver.c: In function ‘qemudMonitorCommand’:
  driver.c:101: warning: empty body in an if-statement

If you have empty  do{}while(0)   then gcc won't complain.

So all we need do is drop the extra ';' from the #define for qemudDebug,
but keep the empty loop

Dan.
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