On Tue, 6 Sep 2005, [EMAIL PROTECTED] wrote:
> On Tue, Sep 06, 2005 at 03:13:48PM -0400, Robert P. J. Day wrote:
> >
> > i'm looking at some legacy code and, in a header file, i find the
> > following (paraphrased for brevity):
> >
> > typedef struct {
> > ... stuff ...
> > } Widgets ;
> >
> > extern Widgets Widget ;
> >
> >
> > huh? i can see why a header file would want to define a structure
> > but i'm confused why the *header* file would then refer to an external
> > object of that type. that's a new one on me -- typically, i'd expect
> > a *source* file to define such a thing and other *source* files to
> > contain the "extern" declaration.
> >
> > is this some subtle programming cleverness of which i am unaware?
> > thanks.
> >
> This is done quite frequently when a data structure needs to be
> referenced from multiple locations. They're not necessicarily
> consecutive like that, but its rather a common practice to extern a
> instance of a type in a header file. The kernel source tree does
> this very frequently, check include/net/ipv4 for lots of examples.
ok, so what it represents is just a shortcut so that each source file
doesn't have to have its own extern, it just comes along with the
header file. all right, i guess i can live with that although it
strikes me as just a little bit sleazy. oh, well.
rday
-
To unsubscribe from this list: send the line "unsubscribe linux-c-programming"
in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
