介绍

显示了一个helloworld示例，该示例对源文件和include文件使用不同的文件夹。
本教程中的文件包括：

B-hello-headers$ tree
.
├── CMakeLists.txt
├── include
│   └── Hello.h
└── src
    ├── Hello.cpp
    └── main.cpp

CMakeLists.txt - 包含要运行的CMake命令
include/Hello.h - 头文件
src/Hello.cpp - 资源文件
src/main.cpp - main文件

概念

目录路径

CMake语法指定了许多变量，这些变量可用于帮助在项目或源树中查找有用的目录。其中包括：

变量	信息
CMAKE_SOURCE_DIR	资源根目录
CMAKE_CURRENT_SOURCE_DIR	当前源目录（如果使用子项目和目录）
PROJECT_SOURCE_DIR	当前cmake工程的源目录
CMAKE_BINARY_DIR	二进制/构建目录的根目录，你可以在这个目录运行cmake命令
CMAKE_CURRENT_BINARY_DIR	当前构建目录
PROJECT_BINARY_DIR	当前项目构建目录

源文件变量

创建一个包含源文件的变量可以让您更清楚地了解这些文件，并轻松地将它们添加到多个命令中，例如add_executable( )函数。

# Create a sources variable with a link to all cpp files to compile
set(SOURCES
    src/Hello.cpp
    src/main.cpp
)

add_executable(${PROJECT_NAME} ${SOURCES})

也可以用GLOB命令去匹配通配符。

file(GLOB SOURCES "src/*.cpp")

不建议将CMake用于变量。取而代之的是在add_xxx函数中直接声明源代码。
这对于glob命令尤其重要，如果添加新的源文件，这些命令可能不会始终显示正确的结果。

头文件目录

在有多个include目录时，用target_include_directories( ) 函数使编译器能够知道头文件位置，编译的时候将添加这些目录到编译器，用 -I ，如：-I/directory/path

target_include_directories(target
    PRIVATE
        ${PROJECT_SOURCE_DIR}/include
)

私有标识符指定include的作用域。在接下来的例子中说明了这一点。

构建例子

标准输出

构建此示例的标准输出如下所示。

$ mkdir build

$ cd build

$ cmake ..
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- 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/hello_headers/build

$ make
Scanning dependencies of target hello_headers
[ 50%] Building CXX object CMakeFiles/hello_headers.dir/src/Hello.cpp.o
[100%] Building CXX object CMakeFiles/hello_headers.dir/src/main.cpp.o
Linking CXX executable hello_headers
[100%] Built target hello_headers

$ ./hello_headers
Hello Headers!

详细输出

在前面的示例中，当运行make命令时，输出仅显示生成的状态。要查看完整的输出以进行调试，可以在运行make时添加VERBOSE=1标志。
详细的输出如下所示，对输出的检查显示了添加到c++编译器命令中的include目录。

$ make clean

$ make VERBOSE=1
/usr/bin/cmake -H/home/matrim/workspace/cmake-examples/01-basic/hello_headers -B/home/matrim/workspace/cmake-examples/01-basic/hello_headers/build --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build/CMakeFiles /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/matrim/workspace/cmake-examples/01-basic/hello_headers/build'
make -f CMakeFiles/hello_headers.dir/build.make CMakeFiles/hello_headers.dir/depend
make[2]: Entering directory `/home/matrim/workspace/cmake-examples/01-basic/hello_headers/build'
cd /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/matrim/workspace/cmake-examples/01-basic/hello_headers /home/matrim/workspace/cmake-examples/01-basic/hello_headers /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build/CMakeFiles/hello_headers.dir/DependInfo.cmake --color=
make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/01-basic/hello_headers/build'
make -f CMakeFiles/hello_headers.dir/build.make CMakeFiles/hello_headers.dir/build
make[2]: Entering directory `/home/matrim/workspace/cmake-examples/01-basic/hello_headers/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build/CMakeFiles 1
[ 50%] Building CXX object CMakeFiles/hello_headers.dir/src/Hello.cpp.o
/usr/bin/c++    -I/home/matrim/workspace/cmake-examples/01-basic/hello_headers/include    -o CMakeFiles/hello_headers.dir/src/Hello.cpp.o -c /home/matrim/workspace/cmake-examples/01-basic/hello_headers/src/Hello.cpp
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build/CMakeFiles 2
[100%] Building CXX object CMakeFiles/hello_headers.dir/src/main.cpp.o
/usr/bin/c++    -I/home/matrim/workspace/cmake-examples/01-basic/hello_headers/include    -o CMakeFiles/hello_headers.dir/src/main.cpp.o -c /home/matrim/workspace/cmake-examples/01-basic/hello_headers/src/main.cpp
Linking CXX executable hello_headers
/usr/bin/cmake -E cmake_link_script CMakeFiles/hello_headers.dir/link.txt --verbose=1
/usr/bin/c++       CMakeFiles/hello_headers.dir/src/Hello.cpp.o CMakeFiles/hello_headers.dir/src/main.cpp.o  -o hello_headers -rdynamic
make[2]: Leaving directory `/home/matrim/workspace/cmake-examples/01-basic/hello_headers/build'
/usr/bin/cmake -E cmake_progress_report /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build/CMakeFiles  1 2
[100%] Built target hello_headers
make[1]: Leaving directory `/home/matrim/workspace/cmake-examples/01-basic/hello_headers/build'
/usr/bin/cmake -E cmake_progress_start /home/matrim/workspace/cmake-examples/01-basic/hello_headers/build/CMakeFiles 0

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