Apprendre Specifying Include Directories | Libraries, Includes, and Build Types

In real projects, header files are usually stored in a separate include/ directory. To allow the compiler to locate these headers, CMake must be told where to look. This is done using the target_include_directories command, which attaches include paths directly to a specific target.

CMakeLists.txt


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cmake_minimum_required(VERSION 3.10)
project(SampleIncludeProject)

add_library(mylib src/mylib.c)
target_include_directories(mylib PUBLIC include)

add_executable(main src/main.c)
target_link_libraries(main PRIVATE mylib)

In this example, target_include_directories(mylib PUBLIC include) tells CMake to add the include/ directory to the compiler’s search path for the mylib library. Because PUBLIC is used, any executable that links to mylib also receives this include path automatically.

Note

Include directories should be assigned to specific targets instead of being applied globally. This keeps your build configuration clean and avoids accidental dependencies.

Controlling Header Visibility

CMake allows you to control who can see which headers. This helps maintain clear boundaries between public APIs and internal implementation details.

CMakeLists.txt


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cmake_minimum_required(VERSION 3.10)
project(IncludeVisibilityExample)

add_library(core src/core.c)
target_include_directories(core
    PUBLIC include/core
    PRIVATE src/private_headers
    INTERFACE include/interfaces
)

add_executable(main src/main.c)
target_link_libraries(main PRIVATE core)

Here, include/core is visible to both the core library and any program that links to it. The src/private_headers directory is used only inside the library and is hidden from other targets. The include/interfaces directory is not used by the library itself but becomes visible to anything that links against it.

This setup enforces encapsulation and prevents consumers of the library from relying on internal headers.

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Section 4. Chapitre 3

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Can you explain the difference between PUBLIC, PRIVATE, and INTERFACE in more detail?

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CMakeLists.txt


              12345678
            
cmake_minimum_required(VERSION 3.10)
project(SampleIncludeProject)

add_library(mylib src/mylib.c)
target_include_directories(mylib PUBLIC include)

add_executable(main src/main.c)
target_link_libraries(main PRIVATE mylib)

Note

Include directories should be assigned to specific targets instead of being applied globally. This keeps your build configuration clean and avoids accidental dependencies.

Controlling Header Visibility

CMake allows you to control who can see which headers. This helps maintain clear boundaries between public APIs and internal implementation details.

CMakeLists.txt


              123456789101112
            
cmake_minimum_required(VERSION 3.10)
project(IncludeVisibilityExample)

add_library(core src/core.c)
target_include_directories(core
    PUBLIC include/core
    PRIVATE src/private_headers
    INTERFACE include/interfaces
)

add_executable(main src/main.c)
target_link_libraries(main PRIVATE core)

This setup enforces encapsulation and prevents consumers of the library from relying on internal headers.

Tout était clair ?

Merci pour vos commentaires !

Section 4. Chapitre 3