How to Access CMake Variables in Your C Code?

Accessing CMake Variables in C Code

When working with CMake, it can be beneficial to store frequently used values as variables. However, accessing these variables within C source code can be challenging.

One approach to using CMake variables in C is to utilize the add_definitions function. This technique enables the passing of variables as preprocessor definitions:

<code class="cmake">add_definitions(-DVERSION_LIBINTERFACE=${LIBINTERFACE_VERSION})</code>

Subsequently, in C code, the variable can be accessed as a preprocessor macro:

<code class="c++">#if defined(VERSION_LIBINTERFACE)
    unsigned int libInterfaceVersion = VERSION_LIBINTERFACE;
#endif</code>

Alternatively, you can leverage the configure_file command to generate a header file template that includes the necessary variable replacements. For instance, create a template file named version_config.h.in:

<code class="c++">#ifndef VERSION_CONFIG_H
#define VERSION_CONFIG_H

#define VERSION_LIBINTERFACE @LIBINTERFACE_VERSION@

#endif</code>

Within the CMakeLists.txt file, utilize the configure_file directive:

<code class="cmake">configure_file(version_config.h.in ${CMAKE_BINARY_DIR}/generated/version_config.h)
include_directories(${CMAKE_BINARY_DIR}/generated/)</code>

Ensure that the generated header file is included in applicable source files.

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