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

[Joe Shaw <joeshaw novell com>]

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.

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.

Joe