Introduction to cmake
Functions
If you stick to certain rules how to structure your project then the CMake files can look very similar. Like duplicated code.
Wouldn't it be nice if we could extract common code to functions?
That's exactly what we are going to do in the last exercise.
The CMake Language
But before we start, let's have a look at a few properties of the CMake language.
All CMake variables are stored as strings.
But in certain contexts, a string may be treated as a list.
Lists are basically strings divided into elements by splitting on ; characters.
Variables are set with command set.
Examples:
set(WHO "John")
set(WHAT "Fruit")
set(${WHO}_${WHAT} "apple") # sets John_Fruit to "apple"
message(STATUS "${Who} wants an ${${WHO}_${WHAT}}") # John wants an apple
set(X a b "c;d" "e f") # X is "a;b;c;d;e f"
One of the most important command for functions is cmake_parse_arguments
A full list of all commands can be found here.
Exercise 7
Implement these functions, so that the CMake files can be written as follows:
- add_interface()
- add_component()
- add_application()
[project]/CMakeLists.txt
# [project]/CMakeLists.txt
cmake_minimum_required(VERSION 3.10)
project("TimeMachine" VERSION 1.0.2 LANGUAGES CXX)
include(project_helper.cmake)
add_subdirectory(vendor)
add_subdirectory(settings)
add_subdirectory(time_travel_interface)
add_subdirectory(flux_capacitor)
add_subdirectory(time_display)
add_subdirectory(time_machine)
[project]/time_machine/CMakeLists.txt
# [project]/time_machine/CMakeLists.txt
add_application(time_machine_app PACKAGE time_machine
SOURCES
src/main.cc
COMPONENTS
time_machine::time_machine
)
add_component(time_machine PACKAGE time_machine
SOURCES
src/time_machine.cc
INCLUDES include
USING
time_machine::flux_capacitor
time_machine::time_display
TESTS
tests/time_machine.cc
)
[project]/flux_capacitor/CMakeLists.txt
# [project]/flux_capacitor/CMakeLists.txt
add_component(flux_capacitor PACKAGE time_machine
SOURCES
src/capacitor.cc
src/flux.cc
src/flux_capacitor.cc
INCLUDES include
SHARING
time_machine::time_travel
TESTS
tests/capacitor.cc
tests/flux_capacitor.cc
tests/flux.cc
)
[project]/time_display/CMakeLists.txt
# [project]/time_display/CMakeLists.txt
add_component(time_display PACKAGE time_machine
SOURCES
src/colors.cc
src/display.cc
src/numbers.cc
INCLUDES include
USING
time_machine::time_travel
TESTS
tests/colors.cc
tests/numbers.cc
tests/time_display.cc
)
[project]/time_travel_interface/CMakeLists.txt
# [project]/time_travel_interface/CMakeLists.txt
add_interface(time_travel PACKAGE time_machine
INCLUDES include
)
Run CMake
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