[gdal-dev] a possible memory leak in ogr\ogrsf_frmts\sqlite

[Even Rouault]

Deyan

this sounds more like "still reachable" memory in Valgrind terminology 
(https://valgrind.org/docs/manual/faq.html#faq.deflost), that is memory 
that is allocated by some component, still reachable by it but never 
explicitly freed before the end of the process, and the amount of it 
doesn't grow over time. There are certainly many similar such patterns 
in GDAL or other libraries it uses, and I don't see that as a bug or 
something that requires code changes.

Even

Le 06/02/2025 à 11:34, Deyan Vasilev via gdal-dev a écrit :
> Hello,
>
> I was chasing for a long time a small 8 byte memory leak and was able
> to identify it in the OGR sqlite extension binding, here's what I
> observed:
>
> A call to OGRSQLiteBaseDataSource::OpenOrCreateDB() would invoke
> OGR2SQLITE_Register() and then sqlite3_auto_extension(). The latter is
> a sqlite3 call that would malloc an 8 byte buffer for the extension
> function entry point if the extension is unknown to sqlite3 (was not
> previously registered).
>
> This allocation seems to be unmanaged neither by sqlite3 nor by OGR
> later causing an 8 byte memory leak.  I was able to resolve this by
> adding a OGR2SQLITE_UnRegister() stub in ogrsqlitevirtualogr.cpp that
> would call in a succession:
>
> sqlite3_cancel_auto_extension ((void (*)(void)) OGR2SQLITE_static_register);
> sqlite3_reset_auto_extension ();
> <
>
> and then have the OGR2SQLITE_UnRegister() stub called in
> ogrsqlitedatasource.cpp \ OGRSQLiteBaseDataSource::CloseDB() right
> after closing the database:
>
>          sqlite3_close( hDB );
>          hDB = nullptr;
>          OGR2SQLITE_UnRegister();
> <
>
> This way the memory leak was gone. My app runs on VS2015/2019 with an
> older GDAL release (2.4.4.) so the fix will be a bit different in 3.10
> as the HAVE_SQLITE3EXT_H conditionals were not present in 2.4.4..
>
> Best regards,
> Deyan
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