Cmake tutorial series-01-minimum configuration example

1. With the smallest cmake Configuration as an example

eg：

cmake_minimum_required(VERSION 3.0)
project(sample CXX)
add_library(sample sample.cpp)
add_executable(sample_exe sample_exe.cpp)

2.cmake_minimum_required

• This function specifies the cmake Minimum version .
• because cmake It's still evolving , Each version will modify some function parameters , More functions will also be added . This function is used to prevent the use of too low version cmake To configure an unexpected error .

3.project

This function declares the name of the project .

Because a project may contain multiple libraries or multiple executable programs , In sub Library / It is forbidden to use the same name as in the function declaration in the sub executable .

The second parameter of the function is the code type of the project .

• It can be stated that C or CXX or C CXX.
• The corresponding represents pure c engineering , pure c++ Engineering and mixed engineering .

Be careful ： Declared code types affect compiler selection .

As mentioned above , Every cmake All projects should declare this keyword , This affects the properties of the entire project .cmake The corresponding variables of the project will also be provided

• PROJECT_NAME Project name
• PROJECT_SOURCE_DIR Project source code root directory
• PROJECT_VERSION Project version
• PROJECT_BINARY_DIR Temporary binary directories generated by the project , Used to store configuration / Compile intermediate files .

4.add_library / add_executable

The first parameter represents the Library / The name of the executable .

The second parameter represents the source file used by the binary to be generated .

• You can use list variables here .
• You can also add the source file name directly .
• You can also use functions later target_source Add source file .
• Be careful ： Statement win32 When the program is executable , Should be in add_executable Add keyword after program name in WIN32 .

add_library You can also add other keywords, such as ：

• SHARED Declare that the library is only generated as a dynamic library
• STATIC Declare that the library is only generated as a static library
• OBJECT Declare that target Only intermediate binary file , For others target Use
• INTERFACE Declare that library is only an interface and does not have its own binary
• ALIAS Declare that this library is only an alias for other libraries
• IMPORTED Declare that the library does not need to be built , Instead, the specific configuration has been imported . This method usually exists in the configuration provided by the dependency .
• When the first five keywords are not stated , The build type of the library depends on BUILD_SHARED_LIBS change .

5. keyword target

target stay cmake Is a very important concept , You should understand it as a object.
It contains, for example, the following ：

• List of related source files
• Related compilation options
• Related dependency Libraries
• List of related header file paths
• List of related library file paths
• Other related properties

therefore , You can use this later target Name do anything . Corresponding cmake The function will use this name to automatically extract the attribute values that the function needs to use .

6. keyword PUBLC PRIVATE INTERFACE

These keywords are used to build dependencies .

• PUBLIC Declare the subsequent values of the keyword in building the target When using , And provide... To the downstream .

• PRIVATE Declaring the subsequent values of this keyword is only used to build this target When using , Do not provide downstream .

• INTERFACE Declare that the keyword is only provided to downstream , Not building this target When using .

• Reference resources ：CMake Tutorial series -01- Minimum configuration example