如何在我的c ++程序中将GDAL库用作可选库？

Question

I am creating a c++ program that can use GDAL (if present). I can check the presence of GDAL in the system but how I need to code my program to include/not include the GDAL libraries if my program was compiled using GDAL?

Many thanks, Carlos.

Answer 1

While I haven't used CMake, but if the library is available you can link with it and also pass a flag to the compiler defining a macro (eg -DHAVE_GDAL ). Then in your source you use the preprocessor to check for HAVE_GDAL and only use GDAL functionality if it's defined.

Something like this in your source:

#ifdef HAVE_GDAL
// Use GDAL functionality
#else
// Use something else
#endif

Answer 2

Generally speaking, if you link your application to a shared object (DLL), your program will fail to start if the shared object is missing. I'm not sure if there's another way than to simply load the SO on startup, and if you get a handle to the library, use dlsym (or GetProcAddress on Windows) to get hold of the functions you need, and call them that way.