[geos-devel] Encounter Segmentation Fault with GEOS 2.2.2

[Mateusz Loskot]

Sheng Liang (SH/CBC) wrote:
> Hi: I encountered an error of "Segmentation Fault" with GEOS 2.2.2.
> What I am doing is to get intersection of two polygons. The error
> happens to the specific polygong: POLYGON ((125.331 0,3.35823e-06
> 125.331,-125.331 6.71646e-06,-1.00747e-05 -125.331,125.331 0)) and 
> POLYGON ((245.331 120,120 245.331,-5.331 120,120 -5.331,245.331 120))
>  There is no error to others polygons. So I think it must be an error
> of GEOS 2.2.2 code.
> 
> My code is : GEOSGeom aPolygon1,aPolygon2; string aString1("POLYGON
> ((125.331 0,3.35823e-06 125.331,-125.331 6.71646e-06,-1.00747e-05
> -125.331,125.331 0))");
> 
> string aString2("POLYGON ((245.331 120,120 245.331,-5.331 120,120
> -5.331,245.331 120))");
> 
> aPolygon1 = GEOSGeomFromWKT(aString1.data());
> aPolygon2 = GEOSGeomFromWKT(aString2.data());

I'm suer in 99% that the problem is in your code above.
You should not access internal buffer of std::string with data() member
function. It should be used in very rare cases because it breaks OOP
rule of encapsulation! It's available only for C compatibility.

GEOSGeomFromWKT expects to get const char* :
Geometry *GEOSGeomFromWKT(const char *wkt);

so, you should call it as follows:

aPolygon1 = GEOSGeomFromWKT(aString1.c_str());

std::string::c_str() returns const char*.

Cheers
-- 
Mateusz Loskot
http://mateusz.loskot.net