[gdal-dev] GDAL_COMPILATION and standalone plugins

[Even Rouault]

Andrew,

You can redefine safely the definition of your GDALRegisterXXXX() 
function in your driver code (prvided you use the same signature as in 
gdal_frmts.h of course)

GDAL_COMPILATION is used to protect "private" GDAL functions that we 
don't want external users of the C++ API to be able to access.

As cmake/helpers/SetupStandalonePlugin.cmake is designed for code that 
is in the GDAL source code tree, it is logical it sets GDAL_COMPILATION

Even

Le 25/03/2026 à 14:30, Andrew C Aitchison via gdal-dev a écrit :
>
> When should GDAL_COMPILATION be set ?
>
> I would like a source tree for a driver.
> Ideally it would be possible to build this in tree (both
> as a plugin or compiled into libgdal.so) and standalone against
> an existing gdal installation (with development libraries and headers).
>
> I thought that GDAL_COMPILATION was a way to tell whether my driver
> was being built as part of gdal, but I find that
> cmake/helpers/SetupStandalonePlugin.cmake includes
> cmake/helpers/GdalCompilationFlags.cmake which sets GDAL_COMPILATION
>
> Why do I care ?
> An in tree build will declare my GDALRegister function in
>    gcore/gdal_frmts.h
> (since it will be used in
>    frmts/gdalallregister.cpp
> ) but an out of tree build will need to declare this itself.
> I thought that testing GDAL_COMPILATION would be the way to avoid my
> GDALRegister function being declared twice under some circumstances.
>
> Any idea what I am missing or misunderstanding ?
>
> Thanks,
>
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