msAddLabel causes segfault when passed a NULL labelObj

[dmorissette]

Tamas reported via mapserver-dev that in msEmbedScalebar msAddLabel is invoked with the following parameters:

msAddLabel(map, l, 0, -1, -1, &point, NULL, " ", 1.0, NULL);

the last parameter causes a segfault in the msAddLabel function.

[dmorissette]

Fixed in r6276

This is related to the recent changes to implement label priority. I didn't know that msAddLabel() could be called with a NULL labelObj.

I just found out that msAddLabel() already contained code to use the class label if the label arg is NULL. The fix for the current bug was simply to make sure this is run before the code that looks up the priority level.

With respect to the embedded scalebar and legend, I've also made a change to set their priority level to MS_MAX_PRIORITY_LEVEL in the temporary layerObj that is used to render them so that they take precedence over any map label.

[dmorissette]

Steve, I added you to CC to ask if you knew of cases other than embedded scalebars and legends that use the labelcache this way and that should be set to MS_MAX_LABEL_PRIORITY

[tamas]

Ok, that's working by now.

[sdlime]

There is a POSTLABELCACHE option for layers so that you can draw things like copyrights after all labels render but that is independent of the cache. So *I think* all is well.

Steve