Re: [gdal-dev] OGRFree(pszSrcWKT) can crash Matlab

jluis Sat, 23 Jan 2010 09:48:03 -0800

Quoting Even Rouault <even.roua...@mines-paris.org>:

Joaquim,
you don't provide enough code to really see what's wrong, but myguess is that you misuse GDAL API.


Even

Quite possible the first and I was trying to summarize what happens


If you get pszSrcWKT, with

pszSrcWKT = GDALGetProjectionRef(hDS);



No, I got it from oSrcSRS.exportToWkt( &pszSrcWKT );

See lines 325 & 329 of

code.google.com/p/mirone/source/browse/trunk/mex/gdalwarp_mex.cpp

Joaquim

The pszSrcWKT string is owned by the hDS object, so as soon as youdestroy the hDS object with GDALClose(), the pointer becomes invalidand points to arbitrary data.

For the same reason, you should never free the string returned byGDALGetProjectionRef() with OGRFree() or any other free() call.


See http://gdal.org/classGDALDataset.html :

GDALDataset::GetProjectionRef() :

returns:

a pointer to an internal reference string. It should not be altered,freed or expected to last for long.


Best regards,

Even

Le Saturday 23 January 2010 16:04:58 jl...@ualg.pt, vous avez écrit :

Hi,

I have a serious crash in one of my Matlab MEXs caused by a call to
OGRFree() with an argument of size one (possibly the  null terminator).
This happens on OSX SL (64 bits) but not on Windows (where I still
build at 32 bits)

Here is, as far as I could trace it, what is happening (SVN version of
the same age as GDAL1.7RC1)

mexPrintf("---- %s\n%s\n", pszSrcWKT,pszDstWKT);

That prints

---- GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS
84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNI
T["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","43
26"]] PROJCS["UTM Zone 29, Northern Hemisphere",GEOGCS["WGS
84",DATUM["WGS_1984",SPHEROID["WGS
84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNI
T["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","43
26"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PA
RAMETER["central_meridian",-9],PARAMETER["scale_factor",0.9996],PARAMETER["f
alse_easting",500000],PARAMETER["false_northing",0],UNIT["Meter",1]]


Next the code does:

        GDALClose( hSrcDS );
mexPrintf("---- %s\n%s\n", pszSrcWKT,pszDstWKT);

and now pszSrcWKT is empty. See

---- 
PROJCS["UTM Zone 29, Northern Hemisphere",GEOGCS["WGS
84",DATUM["WGS_1984",SPHEROID["WGS
84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNI
T["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","43
26"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PA
RAMETER["central_meridian",-9],PARAMETER["scale_factor",0.9996],PARAMETER["f
alse_easting",500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

If I make it print the size of pszSrcWKT  with strlen(pszSrcWKT) the
answer is 1 and finally the MEX (and the entire MATLAB) crash on the
call

OGRFree(pszSrcWKT);


Joaquim Luis

----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.

_______________________________________________
gdal-dev mailing list
gdal-dev@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/gdal-dev




----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.

_______________________________________________
gdal-dev mailing list
gdal-dev@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/gdal-dev

Re: [gdal-dev] OGRFree(pszSrcWKT) can crash Matlab

Reply via email to