CMake

CMake特点

1. open source
2. 跨平台，并可生成native编译配置文件，在Linux/Unix平台，生成makefile，在MacOS平台，可以生成xcode，在Windows平台，可以生成MSVC的工程文件。

CMake Command

PROJECT

PROJECT(projectname [CXX] [C] [Java])

Pre-defined variable by cmake:

• PROJECT_BINARY_DIR
• PROJECT_SOURCE_DIR

SET

SET(VAR [VALUE] [CACHE TYPE DOCSTRING [FORCE]])
SET(SRC_LIST main.c)
SET(SRC_LIST main.c t1.c t2.c)

改变保存binary的目录:

SET(EXECUTABLE_OUTPUT_PATH ${PROJECT_BINARY_DIR}/bin)
SET(LIBRARY_OUTPUT_PATH ${PROJECT_BINARY_DIR}/lib)

应该把这两条指令写在工程的CMakeLists.txt还是src目录下的CMakeLists.txt? 把握一个简单的原则，在哪里ADD_EXECUTABLE或ADD_LIBRARY，如果需要改变目标存放路径，就在哪里加入上述的定义。

ADD_EXECUTABLE

ADD_EXECUTABLE(hello ${SRC_LIST})

ADD_LIBRARY

ADD_LIBRARY(libname [SHARED|STATIC|MODULE] [EXCLUDE_FROM_ALL] source1 source2 ... sourceN)

不需要写全libhello.so，只需要填写hello即可，cmake系统会自动为你生成 libhello.X

类型有三种:

• SHARED，动态库
• STATIC，静态库
• MODULE，在使用dyld的系统有效，如果不支持dyld，则被当作SHARED对待。

MESSAGE

MESSAGE(<mode> "variable is:" ${myVariable})
MESSAGE(STATUS "variable is:" ${myVariable})

The mode keyword determines the type of message:

(none)	= Important information
STATUS	= Incidental information
WARNING	= CMake Warning, continue processing
AUTHOR_WARNING = CMake Warning (dev), continue processing
SEND_ERROR     = CMake Error, continue processing,
                 but skip generation
FATAL_ERROR    = CMake Error, stop processing and generation

STATUS messages are displayed on stdout. All other message types are displayed on stderr.

Mute messages:

SET(CLEAR_MESSAGE 1)

ADD_COMPILE_OPTIONS, ADD_DEFINITIONS

ADD_COMPILE_OPTIONS

• Add the options to all targets within the directory and its sub-directories. It's handy if you have a library in a directory and you want to add options to all the targets related to the library, but unrelated to all other targets.
• The options are added for the compiler.

ADD_DEFINITIONS

• Add pre-processor definitions, such as -DFOO, -DNDEBUG
• This command can also be used to add compiler options, although CMake doesn't recommend it

Example: use CMake commands

ADD_COMPILE_OPTIONS(-O3 -s -DNDEBUG)

or

ADD_COMPILE_OPTIONS(-O3 -s)
ADD_DEFINITIONS(-DNDEBUG)

Generated flags.make file:

C_FLAGS =  -O3 -s
C_DEFINES =  -DNDEBUG

References:

• Difference between add-compile-options and set CMAKE-CXX-FLAGS

CMake Variables

IF

variable: ${} -- 引用变量

Exception: IF

IF A, not IF ${A}

OS

    if (WIN32)
        message("For MSVC")
    else()
        message("For GCC")
        ADD_DEFINITIONS(-std=gnu++11)
    endif()

MSVC Version

Reference: MSVC_VERSION

1200      = VS  6.0
1300      = VS  7.0
1310      = VS  7.1
1400      = VS  8.0 (v80 toolset)
1500      = VS  9.0 (v90 toolset)
1600      = VS 10.0 (v100 toolset)
1700      = VS 11.0 (v110 toolset)
1800      = VS 12.0 (v120 toolset)
1900      = VS 14.0 (v140 toolset)
1910-1919 = VS 15.0 (v141 toolset)