\\page refdocCMakeInstructions CMake Instructions

A sub-module `CMakeLists.txt` defines one or more _targets_.

A target generally corresponds to an actual build artifact like a (static or shared) library or an executable. Targets are the cornerstone of any modern cmake build system.

A typical module's `CMakeLists.txt` contains

Optionally it might contain a call to [o2_target_root_dictionary](../cmake/O2TargetRootDictionary.cmake) if the module's library requires a Root dictionary.

Note also CMakeLists.txt should be considered as code and so the same care you put into writing code (e.g. do not repeat yourself, comments, etc...) should be applied to CMakeLists.txt. Also, like the rest of our code, we can take of the formatting using the [cmake-format](https://github.com/cheshirekow/cmake_format) tool (that tool is certainly not as robust as `clang-format` but it can get most of the job done easily).

The example outputs below are from a Mac, so the shared library extension is `dylib`. On Linux it would be `so`.

Using the following source dir :

├── lib

│   ├── libO2Ex1.dylib

Using a slightly modified version of the previous example (the [A.h](../Examples/Ex2/include/Ex2/A.h) now uses ClassDef for instance), we'll now add a Root dictionary :

│   ├── libO2Ex2.dylib

│   ├── libO2Ex2.rootmap

Adding an executable to previous example :

That is because the [RPATH](https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/RPATH-handling) was correctly set by CMake for the build tree. It should be set correctly also when installing.

Let's add two basic test2 to our previous example.

├── libO2Ex3.dylib

└── libO2Ex4.dylib

../install-Debug/

├── bin

dummy = 0.07 sec*proc (1 test)

fast = 0.07 sec*proc (1 test)

If a module provides one or more executables, it might be of interest for the users of those executables to have access to a man page for them. Ex5 illustates that use case.

o2_target_man_page([targetName] NAME ex5 SECTION 7)

where `NAME xx` refers to a file `doc/xx.[SECTION].in`, and the actual `targetName` can be found from the base target name (ex5 in that case) using the [o2_name_target](../cmake/O2NameTarget.cmake) function.