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双笙子佯谬老师的【公开课】现代CMake高级教程课程笔记

第 6 章：输出与变量

在运行 cmake -B build 时，打印字符串（用于调试）

message("Hello world!")

❯ cmake --build buildHello world!
-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

message(STATUS “…”) 表示信息类型是状态信息，有 – 前缀

message(STATUS "Hello world!")

❯ cmake --build build-- Hello world!
-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

message(WARNING “…”) 表示是警告信息

message(STATUS "Hello world!")
message(WARNING "This is a warning sign!")

❯ cmake --build build-- Hello world!
CMake Warning at CMakeLists.txt:2 (message):This is a warning sign!-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

message(AUTHOR_WARNING “…”) 表示是仅仅给项目作者看的警告信息

message(STATUS "Hello world!")
message(AUTHOR_WARNING "This is a warning sign!")

❯ cmake --build build-- Hello world!
CMake Warning (dev) at CMakeLists.txt:2 (message):This is a warning sign!
This warning is for project developers.  Use -Wno-dev to suppress it.-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

AUTHOR_WARNING 的不同之处：可以通过 -Wno-dev 关闭

message(STATUS "Hello world!")
message(FATAL_ERROR "This is an error message!")
message(STATUS "after error...")

❯ cmake -B build -Wno-dev
-- Hello world!
-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

message(FATAL_ERROR “…”) 表示是错误信息，会终止 CMake 的运行

❯ cmake --build build
-- Hello world!
CMake Error at CMakeLists.txt:2 (message):This is an error message!-- Configuring incomplete, errors occurred!
See also "/mnt/h/Code/lessonCode/CMakeLession/build/CMakeFiles/CMakeOutput.log".
gmake: *** [Makefile:138: cmake_check_build_system] Error 1

message(SEND_ERROR “…”) 表示是错误信息，但之后的语句仍继续执行

message(STATUS "Hello world!")
message(SEND_ERROR "This is an error message!")
message(STATUS "after error...")

❯ cmake --build build
-- Hello world!
CMake Error at CMakeLists.txt:2 (message):This is an error message!-- after error...
-- Configuring incomplete, errors occurred!
See also "/mnt/h/Code/lessonCode/CMakeLession/build/CMakeFiles/CMakeOutput.log".
gmake: *** [Makefile:138: cmake_check_build_system] Error 1

message 可以用于打印变量

set(myvar "hello world!")
message("myvar is ${myvar}")

❯ cmake --build build
myvar is hello world!
-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

如果 set 没加引号会怎样？会变成分号分割的列表
set(myvar hello world)
其实等价于：
set(myvar "hello;world")

set(myvar hello world!)
message("myvar is ${myvar}")

❯ cmake --build build
myvar is hello;world!
-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

如果 message 没加引号会怎样？会把列表里的字符串当成他的关键字

set(myvar FATAL_ERROR hello)
message("${myvar}")

❯ cmake --build build
FATAL_ERROR;hello
-- Configuring done
-- Generating done
-- Build files have been written to: /mnt/h/Code/lessonCode/CMakeLession/build

结论：除非确实需要列表，建议始终在你不确定的地方加上引号，例如：

set(sources "main.cpp" "mylib.cpp" "C:/Program Files/a.cpp")
message("${sources}")