[gdal-dev] Locked files under Windows

[Roger Bivand]

On Tue, 5 Nov 2013, Even Rouault wrote:

>> Even,
>>
>> Thanks as always for getting back quickly! Yes, the relevant code is (line
>> 475 in rgdal/src/gdal-bindings.cpp):
>>
>>    GDALDataset *pDataset =
>>      (GDALDataset *) R_ExternalPtrAddr(sxpHandle);
>>
>>    if (pDataset == NULL) return(R_NilValue);
>>
>>    installErrorHandler();
>>
>>    GDALDriver *pDriver = pDataset->GetDriver();
>>
>>    const char *filename = pDataset->GetDescription();
>>
>>    GDALDeleteDataset((GDALDriverH) pDriver, filename);
>>
>>    R_ClearExternalPtr(sxpHandle);
>>
>>    uninstallErrorHandlerAndTriggerError();
>>
>> but after this is run, the file remains open. Is GDALDeleteDataset()
>> inappropriate? Should we say GDALClose((GDALDatasetH)pDataset); first; you
>> suggested this instead of pDataset->~GDALDataset(); last year? The file
>> pointers are inside the Dataset objects, so obviously they should be
>> closed. We have tried putting things in various orders, without success so
>> far, I'm afraid.
>
> GDALDeleteDataset() doesn't take the dataset object as a parameter, so it will
> not delete it for you (in the C++ sense of delete... The naming of functions
> is a bit confusing admitedly)
>
> Yes, you need to call GDALClose() before GDALDeleteDataset(), and make sure
> that the handle to the dataset is no used afterwards of course. I mention that
> because I'm not sure what R_ClearExternalPtr() does.

Right - I've been trying this based on your first reply, which put me "on 
track". I think that we have assumed that GDALDeleteDataset() took an open 
dataset and deleted it, closing, freeing and unlinking combined. It makes 
sense, though, to close first after having stored the arguments to 
GDALDeleteDataset(). The R_ClearExternalPtr() function clears the internal 
object in R in which external pointers are stored, so would zombie the 
dataset if applied too early. Initial tests on Linux and Windows are 
promising ...

Thanks again,

Roger

>
>
>>
>> Best wishes,
>>
>> Roger
>>
>
>
>

-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no