[mapserver-dev] Regarding to the issue: segfault on transparent layers with new renderers (#3834)

[Tamas Szekeres]

No comments so far.

I've prepared a fix to show what I've meant by storing the outputformat
instead of the renderer vtable in symbolObj.

https://github.com/szekerest/mapserver/commit/f4a4a2831a3d6228181938c0761fa5caf06c6452

Let me know if such change can be applied in master.

This change also contains a fix for the memory leaks caused by the embedded
scalebar and legend symbols which is necessary for making the refcount
approach to work properly.

We might also utilize MS_REFCNT macros for the outputformat refcount
handling too (which are not yet used), but that would involve further
changes to be made in further files.

Best regards,

Tamas





2014-08-20 17:42 GMT+02:00 Tamas Szekeres <szekerest at gmail.com>:

> Hi Devs,
>
> Regarding to #3834 <https://github.com/mapserver/mapserver/issues/3834>,
> I can see several hacks in the code attempting to fix the issue, but it
> seems we are still running into the same issue by getting a crash in
> msFreeSymbol at the line:
>
> s->renderer->freeSymbol(s);
>
> We've already been discussing about implementing a symbol cache at the
> renderers (and eliminate the need of maintaining back references to the
> renderer at symbolObj), however that seems to require fair amount of coding
> and testing at the first sight.
>
> What if we change the renderer reference in symbolObj from
> rendererVTableObj to outputFormatObj (which contains the vtable)? Since the
> outputformat is reference counted we could make sure the outputformat (and
> the vtable) exists until the corresponding symbolObj is alive?
>
>
> Best regards,
>
> Tamas
>
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