CMakeLists include 问题

include_directories与target_include_directories

include_directories并不会将include继续向外层传播, 导致最外层的executable在编译时无法找到模块中的头文件**

getting_started

Step1

configure_file将一个文件映射到另一个文件, 并且将文件中的变量@VAR@进行替换, 这样能够动态地生成文件。这一步是在cmake阶段就完成的, 当cmake命令执行后, 在项目的二进制文件目录下, 可以找到生成的对应.h文件, 可以发现文件中的@xxx@变量已经被替换掉了。

例如:

而生成的文件, 默认存放在${PROJECT_BINARY_DIR}下, 例如在build目录下, 执行

cmake ..

此时的${PROJECT_BINARY_DIR}就是../build

使用target_include_directories将二进制目录包含进去, 来便于寻找头文件

Step2

要想添加一个库, 要做到:

1. 添加子模块的目录 add_subdirectory
2. 在子模块的CMakeLists中创建库, add_library, 将source文件添加进去
3. 在项目的CMakeLists中, 将子模块创建的lib使用target_link_libraries链接到exe
4. 在项目的CMakeLists中, 将子模块所在的头文件目录target_include_directories包含在内
5. 在生成exe的源文件中, #inlcude “xx.h” 包含子模块的头文件, 并可以使用其中的函数/对象

library与变量

add_library创建的在使用时不加$

set创建的需要加$

Q:如何区分CMakeLists中的库、变量名、字符串？是否还有其他的？

链接问题

之前测试时似乎有一个问题:

文件树结构如下:

|-modules
    |-A
        |-a.h
        |-a.cpp
    |-B
        |-b.h

如果b.h中使用了#include “a.h”, 那么必须将A添加到B的target_link_libraries中。（但是这在报错时候不一定能够被发现），如果报错No such file or directory, 那么一定要检查报错来源的模块是哪个，以确定是模块内部include的问题还是模块之间链接的问题。

循环链接问题

以前我以为cmake会自动处理循环链接, 但事实是我没能链接成功导致根本不够成循环

Q:什么是weak

-- Configuring done (0.4s)
CMake Error: The inter-target dependency graph contains the following strongly connected component (cycle):
  "Basic" of type SHARED_LIBRARY
    depends on "CVF" (weak)
    depends on "CVX" (weak)
  "CVX" of type SHARED_LIBRARY
    depends on "Basic" (weak)
    depends on "CVF" (weak)
  "CVF" of type SHARED_LIBRARY
    depends on "CVX" (weak)
At least one of these targets is not a STATIC_LIBRARY.  Cyclic dependencies are allowed only among static libraries.
CMake Generate step failed.  Build files cannot be regenerated correctly.

STATIC与SHARED的不同

动态链接库与静态链接库的不同

这次不是背八股了，到底为什么不同？使用起来有什么不同？

我们常用的.so到底是什么

cmake, make, ninja, 编译, 生成这些都是什么概念？

PRIVATE, PUBLIC, INTERFACE library的接口

工具

vscode-cmake-tool

.vscode创建settings.json

内容如下:(不显示指定的话, generator会自动选择ninja)

{
    "cmake.configureArgs": [
        "-DENABLE_T02=ON",
        "-DCMAKE_BUILD_TYPE=Release"
    ],
    "cmake.buildDirectory": "${workspaceFolder}/build"
}

等价于命令

cmake -DENABLE_T02=ON -DCMAKE_BUILD_TYPE=Release ..

ctrl+shift+P -> CMake:Configure with CMake Debugger

超级调试代码

假设当前CMakeLists中创建的library为CVX, 其target_link_libraries链接了GlobalLibs库。现在药测试其是否链接成功。

# 获取当前库CVX的 PRIVATE、PUBLIC 和 INTERFACE 包含目录属性
get_target_property(CVX_include_dirs_PRIVATE CVX INCLUDE_DIRECTORIES)
get_target_property(CVX_include_dirs_PUBLIC CVX INTERFACE_INCLUDE_DIRECTORIES)

message(STATUS "CVX PRIVATE INCLUDE_DIRECTORIES: ${CVX_include_dirs_PRIVATE}")
message(STATUS "CVX INTERFACE INCLUDE_DIRECTORIES: ${CVX_include_dirs_PUBLIC}")
# 获取接口库GlobalLibs PRIVATE、PUBLIC 和 INTERFACE 包含目录属性
get_target_property(GlobalLibs_include_dirs_PRIVATE GlobalLibs INCLUDE_DIRECTORIES)
get_target_property(GlobalLibs_include_dirs_PUBLIC GlobalLibs INTERFACE_INCLUDE_DIRECTORIES)

message(STATUS "GlobalLibs  PRIVATE INCLUDE_DIRECTORIES: ${GlobalLibs_include_dirs_PRIVATE}")
message(STATUS "GlobalLibs INTERFACE INCLUDE_DIRECTORIES: ${GlobalLibs_include_dirs_PUBLIC}")

# 检查属性
get_target_property(CVX_include_dirs_PRIVATE CVX INCLUDE_DIRECTORIES)
get_target_property(CVX_include_dirs_PUBLIC CVX INTERFACE_INCLUDE_DIRECTORIES)

get_target_property(CVX_link_libraries_PRIVATE CVX LINK_LIBRARIES)
get_target_property(CVX_link_libraries_PUBLIC CVX INTERFACE_LINK_LIBRARIES)
message(STATUS "============================================================")
message(STATUS "CVX PRIVATE INCLUDE_DIRECTORIES: ${CVX_include_dirs_PRIVATE}")
message(STATUS "CVX INTERFACE INCLUDE_DIRECTORIES: ${CVX_include_dirs_PUBLIC}")

message(STATUS "CVX PRIVATE LINK_LIBRARIES: ${CVX_link_libraries_PRIVATE}")
message(STATUS "CVX INTERFACE LINK_LIBRARIES: ${CVX_link_libraries_PUBLIC}")