Define preprocessor macro through CMake

Question

How do I define a preprocessor variable through CMake   The equivalent code would be  define foo

User · Answer

To do this for a specific target  you can do the following   target compile definitions my target PRIVATE FOO 1 BAR 1    You should do this if you have more than one target that you re building and you don t want them all to use the same flags  Also see the official documentation on target compile definitions

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For a long time  CMake had the add definitions command for this purpose  However  recently the command has been superseded by a more fine grained approach  separate commands for compile definitions  include directories  and compiler options    An example using the new add compile definitions   add compile definitions OPENCV VERSION   OpenCV VERSION   add compile definitions WITH OPENCV2    Or   add compile definitions OPENCV VERSION   OpenCV VERSION  WITH OPENCV2    The good part about this is that it circumvents the shabby trickery CMake has in place for add definitions  CMake is such a shabby system  but they are finally finding some sanity   Find more explanation on which commands to use for compiler flags here  https   cmake org cmake help latest command add definitions html  Likewise  you can do this per-target as explained in Jim Hunziker s answer

User · Answer

The other solution proposed on this page are useful some versions of Cmake  lt  3 3 2  Here the solution for the version I am using  i e   3 3 2   Check the version of your Cmake by using   cmake --version and pick the solution that fits with your needs  The cmake documentation can be found on the official page    With CMake version 3 3 2  in order to create    define foo   I needed to use   add definitions -Dfoo       lt --------HERE THE NEW CMAKE LINE inside CMakeLists txt add executable        target link libraries         and  in order to have a preprocessor macro definition like this other one    define foo 5   the line is so modified   add definitions -Dfoo 5       lt --------HERE THE NEW CMAKE LINE inside CMakeLists txt add executable        target link libraries

[c++] Define preprocessor macro through CMake?

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