[cairo] Potential bug on multiple functions in cairo-clip.c

[Chris Wilson]

On Thu, 2009-06-11 at 09:56 -0700, Jindong (JD) Chen wrote:
> It seems to be a bug to me that, in cairo-1.8.6,  a list of functions
> in cairo-clip.c return
> 
> CAIRO_INT_STATUS_UNSUPPORTED
> 
> although their return type is cairo_status_t.
> 
> CAIRO_INT_STATUS_UNSUPPORTED, which is 100, does not work well with macro
> 
> #define _cairo_status_is_error(status) \
>    (status != CAIRO_STATUS_SUCCESS && status <= CAIRO_STATUS_LAST_STATUS)

Indeed we assert that internal status values cannot be propagated back
to the user. The fact that our internal interfaces return cairo_status_t
where they mean cairo_int_status_t has been annoying me for a long time.
It would be nice to spend the time to clean it up so that stronger type
checkers (sparse, C++) do not warn about our mixing of enums, but since
it's highly unlucky to actually uncover a bug I've not been motivated to
spend the time to do so.


> In my case,
> 
> CAIRO_INT_STATUS_UNSUPPORTED
> 
> is returned from the call to _cairo_gstate_clip() in function
> cairo_clip_preserve(), and cause _cairo_set_error() to choke on it.

This is a bug due to an uninitialized variable, fixed in:
commit a5c1cdf2b030959309e1645bd115f058f1367296
Author: M Joonas Pihlaja <jpihlaja at cc.helsinki.fi>
Date:   Thu Nov 13 12:11:12 2008 +0200

    [clip] Fix uninitialised status return in
_cairo_clip_intersect_mask()
    
    This fixes the clip-all test case crashing for me.

and will be included in the forthcoming 1.8.8 release.

Have fun using Cairo!
-Chris