[gdal-dev] Properly reinitializing PROJ_LIB search paths after supplementary file download

Tue Oct 7 15:16:29 PDT 2025

Even,

Thank you for the suggestion. Calling OSRCleanup() corrected the issue I
was seeing. So, I guess the previously used projections were cached and
because of this the proj-data files weren't being used after download,

On Tue, Oct 7, 2025 at 5:50 PM Even Rouault <even.rouault at spatialys.com>
wrote:

> Le 07/10/2025 à 23:47, David Klaus a écrit :
>
> Even,
>
> I will check on this in a moment. If there are OGR/Proj/GDAL entities on
> the heap/stack -- such as OGRCoordinateTransformation -- will calling
> OSRCleanup cause issues?
>
> That should be fine. You should however avoid any concurrent GDAL call in
> another thread
>
>
> On Tue, Oct 7, 2025 at 5:43 PM Even Rouault <even.rouault at spatialys.com>
> wrote:
>
>> David,
>>
>> does calling OSRCleanup() help ?
>>
>> Even
>> Le 07/10/2025 à 17:00, David Klaus via gdal-dev a écrit :
>>
>> Hello GDAL community,
>>
>> The product that I work on uses the CPP GDAL library for a number of
>> routines. Occasionally, this requires supplementary files -- Currently, we
>> supply proj-data 1.20
>> <https://github.com/OSGeo/PROJ-data/releases/tag/1.20.0>
>> -- which we download when we detect that the dataset is needed. Here's the
>> problem, often GDALRegisterAll() is called before the proj-data 1.20 files
>> are downloaded. From my testing, it appears that if the proj-data 1.20
>> files are not available when GDALRegisterAll() is called, GDAL will not use
>> them regardless of whether or not these files are available later.
>>
>> Now, what I think might be a good solution is appropriately updating
>> GDAL's state after proj-data is downloaded s.t. it is able to detect the
>> proj-data files. But, I'm not sure how to do this. Calling the following
>> seems to produce correct results:
>>
>> GDALDestroy()
>> GDALAllRegister()
>>
>> However, the documentation says the following:
>>
>> ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////FROM
>> DOCUMENTATION///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
>> Finalize GDAL/OGR library.
>>
>> This function calls GDALDestroyDriverManager() and OGRCleanupAll() and
>> finalize Thread Local Storage variables.
>>
>> Prior to GDAL 2.4.0, this function should normally be explicitly called
>> by application code if GDAL is dynamically linked (but that does not hurt),
>> since it was automatically called through the unregistration mechanisms of
>> dynamic library loading.
>>
>> Since GDAL 2.4.0, this function may be called by application code, since
>> it is no longer called automatically, on non-MSVC builds, due to ordering
>> problems with respect to automatic destruction of global C++ objects.
>>
>> *Note: no GDAL/OGR code should be called after this call!*
>> ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////FROM
>> DOCUMENTATION///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
>>
>> So, this doesn't seem like the correct way to address this problem. How
>> should I go about updating GDAL's state s.t. it will detect and read the
>> downloaded supplementary proj-data files? Or, is there something more I
>> should be doing before GDALAllRegister() is called?
>>
>> GDAL Version: GDAL 3.10.3, released 2025/04/01
>> Proj Version: 9.6.0
>>
>> P.S. To get out in front of what I expect to be the first question, yes I
>> am setting the PROJ_LIB environmental variable at runtime to the correct
>> folder. Further, I have tried creating an empty proj-data folder available
>> to GDAL when GDALRegisterAll() is called. This did not change GDAL's
>> behavior. Here is the code I use for setting PROJ_LIB:
>>
>> SetEnvironmentVariable("PROJ_LIB", "c:/path/to/proj-data/folder");
>> _putenv_s("PROJ_LIB", "c:/path/to/proj-data/folder"); // (See:
>> GETENV_NOTE)
>>
>> P.P.S Here is the GETENV_NOTE:
>> // GETENV_NOTE:
>> // _putenv_s() is used to ensure compatibility with getenv(). getenv()
>> operates on environment variables loaded into  the _environ global variable
>> (loaded at "process startup.")
>> // SetEnvironmentVariable() affects the environment variables set for
>> this process but does not change _environ. _putenv_s() updates _environ and
>> ensures compatibility w/
>> // genenv().
>>
>> P.P.P.S I do know that there is a more current proj-data dataset
>> available. We may update to this dataset in the future. But unless that
>> will fix the current issue, I'd rather not do that now.
>>
>>
>> --
>> David Klaus
>> Carlson Software
>>
>>
>> *Disclaimer*
>>
>> The information contained in this communication from the sender is
>> confidential. It is intended solely for use by the recipient and others
>> authorized to receive it. If you are not the recipient, you are hereby
>> notified that any disclosure, copying, distribution or taking action in
>> relation of the contents of this information is strictly prohibited and may
>> be unlawful.
>>
>> _______________________________________________
>> gdal-dev mailing listgdal-dev at lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/gdal-dev <https://lists.osgeo.org/mailman/listinfo/gdal-dev>
>>
>> -- http://www.spatialys.com <http://www.spatialys.com>
>> My software is free, but my time generally not.
>>
>>
>
> --
> David Klaus
> Carlson Software
>
>
> *Disclaimer*
>
> The information contained in this communication from the sender is
> confidential. It is intended solely for use by the recipient and others
> authorized to receive it. If you are not the recipient, you are hereby
> notified that any disclosure, copying, distribution or taking action in
> relation of the contents of this information is strictly prohibited and may
> be unlawful.
>
> -- http://www.spatialys.com <http://www.spatialys.com>
> My software is free, but my time generally not.
>
>

-- 
David Klaus
Carlson Software

Disclaimer

The information contained in this communication from the sender is confidential. It is intended solely for use by the recipient and others authorized to receive it. If you are not the recipient, you are hereby notified that any disclosure, copying, distribution or taking action in relation of the contents of this information is strictly prohibited and may be unlawful.
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