Cmake入门之——Set方法(六)

一概述

set方法是cmake-commands中的脚本方法，用于给下面的变量设置值：

一般变量(Set Normal Variable)
缓存变量(Set Cache Entry)
环境变量(Set Environment Variable)

二 Set方法说明

2.1 一般变量(Set Normal Variable)

复制

1	set(<variable> <value>... [PARENT_SCOPE])

variable：只能有一个
value：可以有0个，1个或多个，当value值为空时，方法同unset，用于取消设置的值
PARENT_SCOPE(父作用域)：作用域，除PARENT_SCOPE外还有function scope(方法作用域)和directory scope(目录作用域)

2.2 缓存变量(Set Cache Entry)

复制

1	set(<variable> <value>... CACHE <type> <docstring> [FORCE])

variable：只能有一个
value：可以有0个，1个或多个，当value值为空时，方法同unset，用于取消设置的值
CACHE：关键字，说明是缓存变量设置
type(类型)：必须为以下中的一种：
- BOOL：有ON/OFF，两种取值
- FILEPATH：文件的全路径
- PATH：目录路径
- STRING：字符串
- INTERNAL：字符串
docstring：总结性文字(字符串)
[FORCE]：变量名相同，第二次调用set方法时，第一次的value将会被覆盖

2.3 环境变量(Set Environment Variable)

复制

1	set(ENV{<variable>} [<value>])

variable：只能有一个
value：一般来说，只有一个，为空时，将清除之前设置的变量值，多个时，取值最近的一个，之后的值将被忽略

三示例

3.1 一般变量(Set Normal Variable)

CMakeLists.txt中设置

复制

#normal
set(normal "normalValue")
message(WARNING ${normal})
set(a 1 b 2 "c" [PARENT_SCOPE])
message(WARNING ${a})

Debug输出结果

复制

CMake Warning at CMakeLists.txt:10 (message):
  normalValue

CMake Warning at CMakeLists.txt:12 (message):
  1b2c[PARENT_SCOPE]

3.2 缓存变量(Set Cache Entry)

CMakeLists.txt中设置

复制

# cache
set(isOn ON CACHE BOOL "Bool" [FORCE])
message(WARNING ${isOn})
set(isOFF OFF CACHE BOOL "Bool" )
message(WARNING ${isOFF})

## cache-FILEPATH
set(filePath ${PROJECT_SOURCE_DIR}/CMakeLists.txt CACHE FILEPATH "file path")
message(WARNING ${filePath})
set(filePath ${PROJECT_SOURCE_DIR}/main.cpp CACHE FILEPATH "file path" [FORCE])
message(WARNING ${filePath})

## cache-PATH
set(path ${PROJECT_SOURCE_DIR} CACHE PATH "path")
message(WARNING ${path})
set(path ${PROJECT_BINARY_DIR} CACHE PATH "path" [FORCE])
message(WARNING ${path})

## cache-STRING
set(string cmake CACHE STRING "string")
message(WARNING ${string})
set(string newcmake CACHE STRING "newstring" [FORCE])
message(WARNING ${string})

##cache-internal
set(internal internal CACHE INTERNAL "internal")
message(WARNING ${internal})
set(internal newinternal CACHE INTERNAL "newinternal" [FORCE])
message(WARNING ${internal})

Debug输出结果

复制

CMake Warning at CMakeLists.txt:12 (message):
  ONCACHEBOOLBool[FORCE]

CMake Warning at CMakeLists.txt:14 (message):
  OFF

CMake Warning at CMakeLists.txt:18 (message):
  E:/Code/ClionDemo/CmakeSet/CMakeLists.txt

CMake Warning at CMakeLists.txt:20 (message):
  E:/Code/ClionDemo/CmakeSet/main.cppCACHEFILEPATHfile path[FORCE]

CMake Warning at CMakeLists.txt:24 (message):
  E:/Code/ClionDemo/CmakeSet

CMake Warning at CMakeLists.txt:26 (message):
  E:/Code/ClionDemo/CmakeSet/cmake-build-debugCACHEPATHpath[FORCE]

CMake Warning at CMakeLists.txt:30 (message):
  cmake

CMake Warning at CMakeLists.txt:32 (message):
  newcmakeCACHESTRINGnewstring[FORCE]

CMake Warning at CMakeLists.txt:36 (message):
  internal

CMake Warning at CMakeLists.txt:38 (message):
  newinternalCACHEINTERNALnewinternal[FORCE]

3.3 环境变量(Set Environment Variable)

CMakeLists.txt中设置

复制

message(WARNING $ENV{JAVA_HOME}) #JAVA_HOME是windows中设置的变量
set(ENV{JAVA_HOME} 1)
message(WARNING $ENV{JAVA_HOME})

set(ENV{DEFINE} DEFINE  DEFINE2 DEFINE3) #自定义的变量
message(WARNING $ENV{DEFINE})

set(a) #没有value值，a值清空
message(WARNING ${a})

Debug输出结果

复制

CMake Warning at CMakeLists.txt:42 (message):
  D:\SoftWare\Java\jdk1.8.0_191

CMake Warning at CMakeLists.txt:44 (message):
  1

CMake Warning at CMakeLists.txt:49 (message):
  DEFINE

CMake Warning at CMakeLists.txt:52 (message):