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Hathaway Zhu
C++

总结CMake

本文参考

入门 CMake的目的：It’s all about targets

cmake语言的语法总结

  • In CMake, every variable is a string. 
  • In CMake, every statement is a command that takes a list of string arguments and has no return value. Arguments are separated by (unquoted) spaces.
  • CMake has a special substitution rule for unquoted arguments. 如果某个argument是通过某个variable来表示的，并且该变量的值含有semicolon,cmake会将该值依据semicolon分开成多个argument。
  • CMake对于quoted arguments却永远不会依据semicolon而分裂成多个arguments, even after substitution.
set(ARGS "EXPR;T;1 + 1")
math(${ARGS})      # Equivalent to calling math(EXPR T "1 + 1")
message("${ARGS}") # Prints: EXPR;T;1 + 1
1. 简单打印

2. 定义变量

In cmake, CMake variables are defined at file scope. 所有的变量都是string类型。定义一个变量需要使用set函数，the set command defines a variable at file scope. The first argument is the name of the variable to assign, and the second argument is its value。 我们可以用定义的变量通过“${ }”来substitute某个string（叫做variable reference），具体如下：

set(THING "funk")
message("We want the ${THING}!")

When a variable is undefined, it defaults to an empty string.

我们可以直接用一个变量variable来定义另一个新的变量：

set(PERSON "JOHN")
set(${PERSON}_NAME "John Goodman")

定义一组变量：cmake语言无法定义类，但是可以通过有相同的prefix定义一组变量:

set(JOHN_NAME "John Smith")
set(JOHN_ADDRESS "123 Fake St")
set(PERSON "JOHN")
message("${${PERSON}_NAME} lives at ${${PERSON}_ADDRESS}.")

定义list:

set(MY_LIST These are separate arguments)
message("${MY_LIST}")  # Prints: These;are;separate;arguments
list(REMOVE_ITEM MY_LIST "separate")   # Removes "separate"
message("${MY_LIST}")    # Prints: These;are;argument

3. 定义函数

Functions run in their own scope. None of the variables defined in a function pollute the caller’s scope. 定义函数需要用function/endfunction。

function(doubleIt VARNAME VALUE)
    math(EXPR RESULT "${VALUE} * 2")
    # Set the named variable in caller's scope
    set(${VARNAME} "${RESULT}" PARENT_SCOPE) 
endfunction()

doubleIt(RESULT "4")   # call the function
message("${RESULT}")   # Prints: 8

4. Including Other Scripts

  • The include command: 运行另一个CMake script(the calling script). 通常用于定义一组函数或者macros. It uses the variable CMAKE_MODULE_PATH as a search path.
  • The find_package command: looks for scripts of the form Find*.cmake and also runs them. often used to help find external libraries. find_package(SDL2) is equivalent to include(FindSDL2.cmake).
  • The add_subdirectory command: creates a new scope, then executes the script named CMakeLists.txt from the specified directory in that new scope. typically use it to add another CMake-based subproject, such as a library or executable, to the calling project.

cmake命令generate的4个文件

  1. CMakeCache.txt
  2. CMakeFiles
  3. Makefile
  4. cmake_install.cmake

target的几种类型

  1. 可执行文件(.exe)。句法:add_executable(exe_ToBeBuilt source.cpp)
  2. shared library(.so)。句法:add_library(lib_ToBeBuilt SHARED source.cpp)
  3. static library(.a)。句法: add_library(lib_ToBeBuilt STATIC source.cpp)
  4. Using a shared lib or static lib(a 3rd-party library)。句法如下：
#  shared library
set(PROJECT_LINK_LIBS libtestStudent.so)
link_directories(~/studentlib_shared/build)

include_directories(~/studentlib_shared/include)

add_executable(libtest libtest.cpp)
target_link_libraries(libtest ${PROJECT_LINK_LIBS})
#  static library
set (PROJECT_LINK_LIBS libtestStudent.a)
link_directories(~/studentlib_static/build)

add_executable(libtest libtest.cpp)
target_link_libraries(libtest ${PROJECT_LINK_LIBS})

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