介绍

CMake 是一个 meta-build system，它支持生成很多构建工具对应的构建文件。这个例子展示如何使用 CMake 产生 nijia build (opens new window) 的构建文件，然后使用 nijia 进行项目构建。

你可以理解为 CMake 是一个高级的构建工具，它能构建出低级的构建工具所需要的构建文件。然后使用低级的构建工具对程序进行编译和汇编。

本例的目录🌲:

.
├── CMakeLists.txt
├── main.cpp

CMakeLists.txt:

# Set the minimum version of CMake that can be used
# To find the cmake version run
# $ cmake --version
cmake_minimum_required(VERSION 3.5)

# Set the project name
project (hello_cmake)

# Add an executable
add_executable(hello_cmake main.cpp)

概念解释

CMake 生成器 (Generator)
CMake 生成器是通过读取 CMakeLists.txt 文件生成低级构建工具的构建文件的工具。可以使用 cmake --help 命令查看 CMake 生成器可以生成哪些构建工具的构建文件:

$ cmake --help
...
...
Generators

The following generators are available on this platform (* marks default):
* Unix Makefiles               = Generates standard UNIX makefiles.
  Green Hills MULTI            = Generates Green Hills MULTI files
                                 (experimental, work-in-progress).
  Ninja                        = Generates build.ninja files.
  Watcom WMake                 = Generates Watcom WMake makefiles.
  CodeBlocks - Ninja           = Generates CodeBlocks project files.
  CodeBlocks - Unix Makefiles  = Generates CodeBlocks project files.
  CodeLite - Ninja             = Generates CodeLite project files.
  CodeLite - Unix Makefiles    = Generates CodeLite project files.
  Sublime Text 2 - Ninja       = Generates Sublime Text 2 project files.
  Sublime Text 2 - Unix Makefiles
                               = Generates Sublime Text 2 project files.
  Kate - Ninja                 = Generates Kate project files.
  Kate - Unix Makefiles        = Generates Kate project files.
  Eclipse CDT4 - Ninja         = Generates Eclipse CDT 4.0 project files.
  Eclipse CDT4 - Unix Makefiles= Generates Eclipse CDT 4.0 project files.

可以看到 CMake 在我的 ubuntu 20.04 上支持生成以上构建工具的构建文件。

Calling a Generator

为了调用 CMake 的 generator 可以在 CMake 构建时使用:

cmake .. -G Ninja

运行完上面命令后就可以直接使用 Ninja 进行构建了。

构建本例

$ mkdir build.ninja

$ cd build.ninja/

$ cmake .. -G Ninja
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler using: Ninja
-- Check for working C compiler using: Ninja -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler using: Ninja
-- Check for working CXX compiler using: Ninja -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/matrim/workspace/cmake-examples/01-basic/J-building-with-ninja/build.ninja

$ ninja -v
[1/2] /usr/bin/c++     -MMD -MT CMakeFiles/hello_cmake.dir/main.cpp.o -MF "CMakeFiles/hello_cmake.dir/main.cpp.o.d" -o CMakeFiles/hello_cmake.dir/main.cpp.o -c ../main.cpp
[2/2] : && /usr/bin/c++      CMakeFiles/hello_cmake.dir/main.cpp.o  -o hello_cmake  -rdynamic && :

$ ls
build.ninja  CMakeCache.txt  CMakeFiles  cmake_install.cmake  hello_cmake  rules.ninja

$ ./hello_cmake
Hello CMake!