How to Prevent Rebuilding Of Dependency In Cmake?

To prevent the rebuilding of dependency in cmake, it is crucial to properly specify all dependencies in the CMakeLists.txt file. This includes setting up accurate target dependencies, as well as including the correct headers and libraries in the project.

Additionally, utilizing CMake's built-in features such as target_link_libraries and target_include_directories can help to ensure that dependencies are properly managed and linked.

Furthermore, using out-of-source builds can also help prevent unnecessary rebuilding of dependencies, as it keeps the build files separate from the source code.

Overall, paying close attention to the organization and management of dependencies in the CMakeLists.txt file, as well as leveraging CMake's features effectively, can help prevent the rebuilding of dependencies in cmake.

How to prevent rebuilding of dependency in CMake?

To prevent the rebuilding of dependencies in CMake, you can use the following strategies:

1. Use CMake's target-specific dependencies: By specifying dependencies at the target level, CMake will only rebuild a target if any of its dependencies have changed. This can help prevent unnecessary rebuilding of dependencies.

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add_executable(my_target main.cpp)
target_link_libraries(my_target 
    PRIVATE dependency1
    PRIVATE dependency2
)

1. Use CMake 3.11 or later with object libraries: Object libraries in CMake do not have a build output, so changes to their sources do not trigger rebuilds of targets that link to them.

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add_library(my_object OBJECT source1.cpp source2.cpp)
add_executable(my_target main.cpp $<TARGET_OBJECTS:my_object>)

1. Enable CMake's dependency checking: CMake has a built-in feature that checks whether the dependencies of a target have changed and only rebuilds them if necessary. You can enable this feature by setting the CMAKE_DEPENDS_USE_COMPILER variable to TRUE.

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set(CMAKE_DEPENDS_USE_COMPILER TRUE)

By using these strategies, you can prevent unnecessary rebuilding of dependencies in CMake and improve the efficiency of your build process.

What settings should I adjust in CMake to prevent dependency rebuilding?

To prevent unnecessary dependency rebuilding in CMake, you can adjust the following settings:

1. CMAKE_SKIP_BUILD_RPATH: By setting this variable to TRUE, CMake will not set the build path in the rpath of executables and shared libraries. This can help prevent unnecessary rebuilds caused by changes in the build path.
2. CMAKE_USE_RELATIVE_PATHS: Setting this variable to TRUE will make CMake use relative paths when storing compiler and linker flags. This can help to prevent dependency rebuilding when the absolute paths change.
3. CMAKE_EXPORT_NO_PACKAGE_REGISTRY: This variable can be set to TRUE to prevent CMake from exporting the package registry during the build process. This can help to prevent rebuilding dependencies when the package registry changes.
4. CMAKE_SKIP_INSTALL_ALL_DEPENDENCY: Setting this variable to TRUE will prevent CMake from installing all dependencies along with the main project. This can help prevent unnecessary dependency rebuilding during the installation process.

By adjusting these settings in your CMake configuration, you can help minimize unnecessary dependency rebuilding and improve the overall build performance of your project.

What are the best practices for managing dependencies in CMake to prevent rebuilding?

1. Use target-based dependencies: Specify dependencies at the target level rather than at the individual file level. This allows CMake to efficiently handle the dependencies and only rebuild targets when necessary.
2. Use ExternalProject_Add for external dependencies: Use ExternalProject_Add function to manage external dependencies that are not built as part of your project. This ensures that external dependencies are only rebuilt when necessary.
3. Use INTERFACE targets for header-only libraries: If you are using header-only libraries, consider creating INTERFACE targets for them. This will help prevent unnecessary recompilation of your project when the header-only library is modified.
4. Use build configuration checks: Use the CheckSymbolExists or CheckFunctionExists commands to check for the availability of symbols or functions in external libraries. This can help prevent unnecessary recompilation of your project when the availability of symbols or functions changes.
5. Use precompiled headers: Utilize precompiled headers to speed up the compilation process and avoid unnecessary recompilation of header files.
6. Use CMake-generated dependency files: CMake can generate dependency files that list the dependencies of each source file. By using these dependency files, CMake can accurately determine when a target needs to be rebuilt based on changes to its dependencies.
7. Use package manager tools: If possible, consider using package manager tools such as Conan or vcpkg to manage external dependencies. These tools can help automate the process of fetching and building external dependencies and ensure that they are managed efficiently.

By following these best practices, you can effectively manage dependencies in CMake to prevent unnecessary rebuilding of your project.

What are the common mistakes that lead to unnecessary dependency rebuilds in CMake?

1. Not using target-specific settings: Dependency tracking in CMake is done at the target level, which means that changing a setting for one target should not trigger a rebuild of all dependent targets. However, if settings are not properly scoped to specific targets, changes can cause unnecessary rebuilds of all targets.
2. Using global settings for include directories: Including directories globally instead of specifying them at the target level can lead to unnecessary rebuilds, as changes to one include directory will trigger a rebuild of all targets that depend on it.
3. Mixing sources and headers in the same directory: CMake uses file timestamps to determine when to rebuild targets. If source and header files are mixed together in the same directory, changes to one file may trigger a rebuild of all targets that depend on that directory, even if only header files were modified.
4. Not using header-only libraries correctly: Header-only libraries do not have any associated build artifacts, so changes to them should not trigger a rebuild of dependent targets. However, if header-only libraries are not handled correctly in CMake, changes can still cause unnecessary rebuilds.
5. Not properly specifying dependencies between targets: CMake allows for specifying dependencies between targets using the target_link_libraries and target_include_directories commands. If these dependencies are not properly specified, CMake may not be able to accurately determine when dependent targets need to be rebuilt.