python mapscript segfault

[Sean Gillies]

Tamas Szekeres wrote:
> 2006/11/9, John Cartwright <John.C.Cartwright at noaa.gov>:
>> Hello All,
>>
>> I'm trying to use python mapscript (4.10.0) on MacOS 10.4 to create a
>> map dynamically and output the image.  Code seems to segfault at the
>> termination of the program.  Can anyone see what I'm doing wrong or
>> suggest a method of tracing the problem?
>>
>> Thanks!
>>
>> -- john
>>
>>
>> import mapscript;
>>
>> map = mapscript.mapObj()
>> map.name = "CustomMap"
>> map.setSize(600,300)
>> map.setExtent(-180.0,-90.0,180.0,90.0)
>> map.imagecolor.setRGB(180,180,250)
>> map.units = mapscript.MS_DD
>>
>> layer = mapscript.layerObj(map)
>> layer.name = "countries"
>> layer.type = mapscript.MS_LAYER_POLYGON
>> layer.status = mapscript.MS_DEFAULT
>> layer.data = "/usr/local/shapefiles/country.shp"
>>
>> class1 = mapscript.classObj(layer)
>> class1.name = "Countries"
>>
>> style = mapscript.styleObj(class1)
>> style.outlinecolor.setRGB(100,100,100)
>> style.color.setRGB(200,200,200)
>>
>> map_image = map.draw()
>> filename = 'test.' + map_image.format.extension
>> map_image.save(filename)
>>
> 
> I've notified the developers about this issue long ago but I can see I
> should repeat the problem again.
> So this is definitely a mapserver issue has been identified originally
> for C# descibed in the following bug:
> 
> http://mapserver.gis.umn.edu/bugs/show_bug.cgi?id=1743
> 
> As looking into the code the problem applies to C# Java and Python but
> might apply to the other
> SWIG variants as well.
> 
> This problem is related to the improper handling of the ownership of
> the memory. For example when calling
> 
> mapscript.layerObj(map) the map object will take the ownership of the
> constructed object so the internal state
> of the layer object should be changed accordingly. That is: setting
> swigCMemOwn = false for Java and C#.
> 
> The most awkward thing that we cannot workaround this issue
> declaratively (like using DISOWN typemaps for example)
> because the ownership should not be transferred when the constructor
> is called with null.
> 
> For the C# binding we could use the following fix (in csmodule.i):
> 
> 
> %typemap(csconstruct, excode=SWIGEXCODE) layerObj(mapObj map) %{:
> this($imcall, true) {
>   if (map != null) this.swigCMemOwn = false;$excode
> }
> %}
> %typemap(csconstruct, excode=SWIGEXCODE) classObj(layerObj layer) %{:
> this($imcall, true) {
>   if (layer != null) this.swigCMemOwn = false;$excode
> }
> %}
> %typemap(csconstruct, excode=SWIGEXCODE) styleObj(classObj
> parent_class) %{: this($imcall, true) {
>   if (parent_class != null) this.swigCMemOwn = false;$excode
> }
> %}
> 
> John,
> Instead of the code above would you try using insertLayer, insertClass
> and insertStyle
> with the newly created layer class and style objects constructed using
> null parameter?
> 

Right. This problem with layerObj(map) is one of the reasons why I wrote 
the insert* methods.

Cheers,
Sean

-- 
Sean Gillies
http://zcologia.com/news