[mapserver-dev] A couple of problems I've found.

[Rahkonen Jukka (Tike)]

Hi,

Mapserver-users may be quiet but not dead. In your case you did not get an answer from there probably because most people which I classify to Mapserver users do not know what is mapdraw.c or mapkmlrenderer.cpp. Thank you still for posting to mapserver-users because now we users know that there can be some trouble with rendering to KML and if we experience something similar we can refer to your mail.

For me it looks like you’ve done good work with debugging and I believe that it will help the developers  to resolve the issue.

-Jukka Rahkonen-

yeryry wrote


Reposting this here as mapserver-users seems pretty dead...
I think I've discovered two causes of crashes...

First, one with the KML driver...

msDrawQueryLayer creates and draws a temporary layer here:
https://github.com/mapserver/mapserver/blob/bdd421c7e69e2ff16841c12c08ba688b62a9f9a6/mapdraw.c#L1209
The KML renderer sets a reference to the temporary layer here:
https://github.com/mapserver/mapserver/blob/bdd421c7e69e2ff16841c12c08ba688b62a9f9a6/mapkmlrenderer.cpp#L371<https://github.com/mapserver/mapserver/blob/3e8aa5a4d92c9bad105306ebe5117ed29d2b0e7c/mapkmlrenderer.cpp#L371>
msDrawQueryLayer later calls msDrawShape here:
https://github.com/mapserver/mapserver/blob/bdd421c7e69e2ff16841c12c08ba688b62a9f9a6/mapdraw.c#L1299<https://github.com/mapserver/mapserver/blob/3e8aa5a4d92c9bad105306ebe5117ed29d2b0e7c/mapdraw.c#L1295>
which eventually results in a call to KmlRenderer::renderGlyphs
https://github.com/mapserver/mapserver/blob/bdd421c7e69e2ff16841c12c08ba688b62a9f9a6/mapkmlrenderer.cpp#L693<https://github.com/mapserver/mapserver/blob/3e8aa5a4d92c9bad105306ebe5117ed29d2b0e7c/mapkmlrenderer.cpp#L693>
which gets to KmlRenderer::createPlacemarkNode and reuses the reference that was set:
https://github.com/mapserver/mapserver/blob/bdd421c7e69e2ff16841c12c08ba688b62a9f9a6/mapkmlrenderer.cpp#L585<https://github.com/mapserver/mapserver/blob/3e8aa5a4d92c9bad105306ebe5117ed29d2b0e7c/mapkmlrenderer.cpp#L585>
even though that temporary layer was freed earlier, leading to the crash.
And one with WMS:

It crashes around here:
https://github.com/mapserver/mapserver/blob/bdd421c7e69e2ff16841c12c08ba688b62a9f9a6/mapdraw.c#L106<https://github.com/mapserver/mapserver/blob/3e8aa5a4d92c9bad105306ebe5117ed29d2b0e7c/mapdraw.c#L106>
Probably due to trying to set NULL->map... That error message should probably be moved before that line.
In my case though, I was trying to serve KML over WMS, so "not having an image" shouldn't really be an error condition? And that non-square-pixels thing also shouldn't be relevant for vector layers; currently the dimensions of the requested WMS "image" have a big effect on KML output coordinates, which strikes me as broken, so perhaps that whole function should be avoided for vector output.
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