Passing compiler options in CMake

by

Yes, you can append compiler and linker options. But there are two things you have to differentiate in CMake: the first call to generate the build environment and all consecutive calls for regenerating that build environment after changes to your CMakeLists.txt files or dependencies.

Here are some of the possibilities (excluding the more complex toolchain variants):

Append Compiler Flags

  1. The initial content from the cached CMAKE_CXX_FLAGS variable is a combination of CMAKE_CXX_FLAGS_INIT set by CMake itself during OS/toolchain detection and whatever is set in the CXXFLAGS environment variable. So you can initially call:

     cmake -E env CXXFLAGS="-Wall" cmake ..

  2. Later, CMake would expect that the user modifies the CMAKE_CXX_FLAGS cached variable directly to append things, e.g., by using an editor like ccmake commit with CMake.

  3. You can easily introduce your own build type like ALL_WARNINGS. The build type specific parts are appended:

      cmake -DCMAKE_CXX_FLAGS_ALL_WARNINGS:STRING="-Wall" -DCMAKE_BUILD_TYPE=ALL_WARNINGS ..

Append Linker Flags

The linker options are more or less equivalent to the compiler options. Just that CMake’s variable names depend on the target type (EXE, SHARED or MODULE).

  1. The CMAKE_EXE_LINKER_FLAGS_INIT, CMAKE_SHARED_LINKER_FLAGS_INIT or CMAKE_MODULE_LINKER_FLAGS_INIT do combine with the evironment variable LDFLAGS to CMAKE_EXE_LINKER_FLAGS, CMAKE_SHARED_LINKER_FLAGS and CMAKE_MODULE_LINKER_FLAGS.

    So you can e.g call:

     cmake -E env LDFLAGS="-rpath=/home/abcd/libs/" cmake ..

  2. See above.

  3. Build type-specific parts are appended:

     cmake -DCMAKE_SHARED_LINKER_FLAGS_MY_RPATH:STRING="-rpath=/home/abcd/libs/" -DCMAKE_BUILD_TYPE=MY_RPATH ..

Alternatives

Just be aware that CMake does provide a special variable to set complier/linker flags in a platform independent way. So you don’t need to know the specific compiler/linker option.

Here are some examples:

Unfortunately, there is none for the compiler’s warning level (yet)

References

More Related Contents:

  1. What is the proper way to use `pkg-config` from `cmake`?
  2. Using CMake with GNU Make: How can I see the exact commands?
  3. Looking for a ‘cmake clean’ command to clear up CMake output
  4. How to set warning level in CMake?
  5. How to set linker flags for OpenMP in CMake’s try_compile function
  6. Compile with /MT instead of /MD using CMake
  7. How to make CMake reconfiguration depend on custom file?
  8. Listing include_directories in CMake
  9. Recursive list of LINK_LIBRARIES in CMake
  10. CMake – linking to library downloaded from ExternalProject_add()
  11. How to instruct CMake to use the build architecture compiler
  12. What is a CMake generator?
  13. Add Source in a subdirectory to a cmake project
  14. Correct way to use third-party libraries in cmake project
  15. CMake compare to empty string with STREQUAL failed
  16. CMake how to set the build directory to be different than source directory
  17. How to always run command when building regardless of any dependency?
  18. how to add prebuilt object files to executable in cmake
  19. How to run ctest after building my project with cmake
  20. Using CMake, how do I get verbose output from CTest?
  21. Difference between add_compile_options and SET(CMAKE_CXX_FLAGS…)
  22. Simple find_package config file example
  23. cmake add_custom_command
  24. Check CMake Cache Variable in Toolchain File
  25. How to tell CMake to use relative paths
  26. Retrieve all link flags in CMake
  27. Specifying build directory within CMakeLists file
  28. How can I debug CMakeLists.txt files?
  29. Linking GLEW with CMake
  30. How to print all the properties of a target in cmake?

Leave a Comment