[osgeo4w-dev] [Qgis-developer] Crash in thread on FILE opened by a lib compiled by MinGW

Radim Blazek radim.blazek at gmail.com
Fri Jun 19 02:49:12 PDT 2015

On Fri, Jun 19, 2015 at 11:32 AM, Even Rouault
<even.rouault at spatialys.com> wrote:
> Le vendredi 19 juin 2015 11:04:39, Radim Blazek a écrit :
>> Hi,
>> I am trying to fix QGIS (compiled by MSVC) crashes with GRASS 7
>> (compiled by MinGW) on Windows. I have traced down that it crashes
>> when functions are called on a FILE structure which was created by a
>> library (libgrass_gis.7.0.0.dll in this case) compiled by MinGW in a
>> thread in an application compiled by MSVC. It crashes in Microsoft
>> _lock_file(FILE *pf) where pf is casted to _FILEX:
>>     EnterCriticalSection( &(((_FILEX *)pf)->lock) );
>> where _FILEX is defined as
>>     typedef struct {
>>         FILE f;
>>         CRITICAL_SECTION lock;
>>     }   _FILEX;
>> Most probably, when the file is opened in a library compiled by MinGW,
>> it is not allocated as _FILEX but as FILE and accessing the lock is
>> causing the crash. Does anybody have deeper insight into the problem
>> and how to solve it?
>> It does not happen with GRASS 6 compiled with MinGW. Are you aware of
>> any difference between GRASS 6 and 7 build in OSGeo4W? E.g. different
>> GCC version or compilation options?
> I cannot comment on this particular case, but in the Windows world, I believe
> the internal layout of FILE structure is specific to the C runtime used, so you
> cannot exchange them between different compilers. If you want to mix them, the
> library must return an opaque pointer to the using code and provide all needed
> functions to manipulate and free it.
> /* Opaque type */
> typedef struct mySuperFile mySuperFile;
> mySuperFile* MyLibReturnFile(...);
> int MyLibReadFile(mySuperFile*, ...); /* use same protype as fread() */
> void MyLibCloseFile(mySuperFile*);

Thanks for your comment. It means that I am probably on a wrong track.
The GRASS lib in fact does all the operations on the file. Because it
is impossible to debug a lib compiled with MinGW when QGIS is compiled
by MSVC and it works OK with GRASS libs compiled with MSVC I have
mixed vector lib compiled by MSVC (which I con debug) with gis lib
compiled by MinGW, which I thought is causing the problem.

I have also created new issue https://hub.qgis.org/issues/13002
and added your comment.


>> It works if the library is compiled by MSVC.
>> Radim
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> http://www.spatialys.com

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