[gdal-dev] Basic plugin questions

[Even Rouault]

Le mardi 03 novembre 2015 16:46:51, David Adler a écrit :
> If a data source is created as a plugin and GDALRegisterAll invokes
> GDALRegister_myDS, won't this cause an error at runtime if the DLL/so is
> not found?

Yes, if you build as plugin, then the #ifdef ENABLE_MYDS shouldn't be defined 
so that GDALRegisterAll() doesn't call GDALRegister_myDS()

> 
> Does GDAL need to be rebuilt specifically to include support for a
> particular plugin and then distributed separately?

Of course not, that's the purpose of the plugin mechanism to not require 
rebuilding GDAL. You just have to make sure to compile the plugin against the 
exact version of GDAL headers you want to run against however.

> 
> Is there a repository for plugin DLL/so and how do the shared libraries
> get there?

Have a look at AutoloadDrivers() in gcore/gdaldrivermanager.cpp

On Unix, plugins will be looked for in ${install_prefix}/share/gdalplugins or 
${install_preifx}/share/gdalplugins/major.minor
Other locations for MacOSX.
And in all cases the GDAL_DRIVER_PATH environment variable can be defined/

> 
> Related to this but for the current non-plugin version of the DB2 OGR
> driver, I added
> #ifdef DB2_ENABLED
>      RegisterOGRDB2();
> #endif
> to
> OGRRegisterAllInternal() in ogrregisterall.cpp
> and
> -DDB2_ENABLED
> to
> ogr\ogrsf_frmts\generic\makefile.vc
> 
> This works ok for the current ODBC-based implementation which has no
> external dependencies, but it would be better to switch to the DB2 CLI
> interface (basically the same as ODBC but supports directly platforms
> other than Windows).
> 
> Please excuse the basic questions as I'm not that familiar with how this
> all works, especially the various macro variables used in makefiles and
> source code.
> 
> Regards,
> David
> 
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