Re: [evolution-patches] Cleanups for evolution/calendar

[Srinivasa Ragavan <sragavan novell com>]

Hi Kjartan,

On Wed, 2006-08-16 at 20:35 +0200, Kjartan Maraas wrote:
> ons, 16,.08.2006 kl. 13.01 -0400, skrev Joe Shaw:
> > Hi,
> > 
> > On Wed, 2006-08-16 at 18:22 +0200, Kjartan Maraas wrote:
> > > > > > On Wed, 2006-08-16 at 16:53 +0200, Kjartan Maraas wrote:
> > > > > > > -               d (printf("%s:%d (list_changed_cb) - Removing Calendar %s\n", __FILE__, __LINE__, l->data));            
> > > > > > > +               d (printf("%p:%d (list_changed_cb) - Removing Calendar %s\n", __FILE__, __LINE__, l->data));            
> > >
> > > I'm a bit baffled by the use of %d for all these structs and pointers.
> > > If the debug output is supposed to show strings to the user they should
> > > all be %s and casted to char * I guess?
> > 
> > %d is only used for the second value, __LINE__, which is a special
> > preprocessor macro set by the compiler.  My understanding is that
> > __LINE__ is just an integer value.  Hence the use of %d.
> > 
> > Likewise, __FILE__ is set in the same way, but it is a string constant.
> > Thus, %s.
> > 
> > The warning is actually for "%s" but references the 4th argument (the
> > format string first, __FILE__ second, __LINE__ third, l->data fourth).
> > The issue is that l->data is defined as a gpointer, but %s implies char
> > *.
> > 
> > l is an element in a GList or GSList and it was designed to be as
> > generic as possible.  That's why the data value is defines as a
> > gpointer: you can store a pointer to a string, pointer to a structure,
> > even an integer casted to a pointer in there.  But the compiler doesn't
> > know exactly what it is and can't automatically cast from a gpointer to
> > the appropriate type.
> 
> Yeah, I follow that.
> 
> > Therefore, it's important for the developer to know what type l->data
> > really is.  I presume it's a string since the %s was already in the
> > format specifier, so just casting l->data to char * is probably the
> > right thing.  Otherwise someone probably would have noticed garbage
> > being printed on the console by now.
> > 
> Looking through the rest of the file almost all debug printouts use %d
> and try to print out pointers to structs, strings and so on. I'm not
> sure what info is really wanted there so maybe the people who added the
> debug statements in the alarm code could chime in and reveal what was
> intended here? :-)
> 
It is a string and casting to (char *) should just solve the problem.
You are right, the %d has to be converted to %p. It was added to debug
the multiple corruptions happening in alarm code. 

> Cheers
> Kjartan
> 
>