On Tuesday, 2018-01-16 19:38:25 +0000, Chuck Atkins wrote:
> > > +#define debug_printf(...) if(mesa_debug) { fprintf(stderr,
> > __VA_ARGS__); }
> >
> > `do {} while(0)`
> >
>
> Forgive me but I don't understand, what you're saying here.
Sorry, I guess I could've used a few more characters to type my message :)
I meant that you could add a `do { X; } while(0)` loop around the `if`
in your macro, so as to avoid the common if/else bug, eg.:
if (foo)
debug_printf("foo");
else
debug_printf("not foo");
Without the `do{}while(0)` trick, this expands into:
if (foo)
if (mesa_debug)
{
fprintf(stderr, "foo");
}
else
if (mesa_debug)
{
fprintf(stderr, "not foo");
}
and you'll never print "not foo".
The usual fix for this class of bugs is to add the `do{}while(0)` loop
as follows:
#define debug_printf(...) \
do { \
if (mesa_debug) { \
fprintf(stderr, __VA_ARGS__); \
} \
} while(0)
>
>
>
> > Why only replace some of the printfs?
> >
>
> The fprintf's I replaced with debug_printf are informational status
> messages, while the ones I left are actual error messages.
My bad, I didn't actually look at them, just noticed they existed :)
>
> - Chuck
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