[geos-devel] Memory problems while parsing WKB

[Mateusz Loskot]

Andreas Volz wrote:
> Am Wed, 18 Apr 2007 20:52:51 +0200 schrieb Mateusz Loskot:
> 
>> Andreas Volz wrote:
>>> Hello,
>>>
>>> I've problems to parse WKB with GEOS. Here is my sample application:
>>> [...]
>>> It works in most cases, but sometimes the result values are broken
>>> or I get a segfault. So I used valgrind to get some more
>>> information. I got this as result:
>>>
>>> ==17755== Invalid read of size 4
>>> ==17755==    at 0x41327FE: geos::PrecisionModel::makePrecise(double)
>>> const (in /usr/lib/libgeos.so.2.2.3) ==17755==    by 0x401D5D5A: ???
>>> ==17755==  Address 0x460A544 is 4 bytes inside a block of size 16
>>> free'd ==17755==    at 0x40212FA: operator delete(void*)
>>> (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so) ==17755==
>>> by 0x4132695: geos::PrecisionModel::~PrecisionModel()
>>> (in /usr/lib/libgeos.so.2.2.3) ==17755==    by 0x42F083B: (below
>>> main) (in /lib/libc-2.5.so) ==17755==
>>>
>>> ... and this as often as I read coordinates.
>>>
>>> Any ideas why PrecisionModel has this problem? A problem in GEOS
>>> WKBParser or my application?
>> Andreas,
>>
>> Could you provide us with simple but generic program presenting the
>> problem? Ideally, if the example:
>> - refers only to GEOS, but not to any database
>> - shows values of coordinates causing the crash, just hardcoded in the
>> program
>>
>> Your code is not usable, because it's specific to your particular
>> environment and data.
> 
> I've created an example without database access:
> 
> http://tux-style.de/osm/tmp/proj_test.zip
> 
> Makefile
> proj_test.cpp
> data.bin         - Binary dump of a database line into a file
> valgrind.txt     - You see the problem only with valgrind (saved output)
> 
> Tell me what else you need if I've not provided enough information.

Andreas,

Thanks for the example.

Could you tell me what version of GEOS do you use?

I suppose it's line of GEOS  2.x because the example
does not compile with 3.x.

Am I correct?

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