动态链接库

## 项目结构
```
linking-libraries/
├── CMakeLists.txt              # 主 CMake 配置
├── main.cpp                    # 主程序
├── libs/                       # 库目录
│   ├── math/                   # 数学库
│   │   ├── math_operations.h
│   │   └── math_operations.cpp
│   ├── string/                 # 字符串库
│   │   ├── string_utils.h
│   │   └── string_utils.cpp
│   └── logger/                 # 日志库
│       ├── logger.h
│       └── logger.cpp
└── README.md                   
```
```
cmake_minimum_required(VERSION 3.15)

project(LinkingLibraries VERSION 1.0)

# 创建数学库
add_library(math_lib STATIC
    libs/math/math_operations.cpp
)
target_include_directories(math_lib PUBLIC libs/math/)

set(CMAKE_C_COMPILER "D:/msys64/mingw64/bin/gcc.exe")
set(CMAKE_CXX_COMPILER "D:/msys64/mingw64/bin/g++.exe")

# 创建字符串处理库
add_library(string_lib STATIC
    libs/string/string_utils.cpp
)
target_include_directories(string_lib PUBLIC libs/string/)

# 创建日志库
add_library(logger_lib STATIC
    libs/logger/logger.cpp
)
# **作用**：告诉编译器在哪里查找 logger_lib 需要的头文件
# 使用 PUBLIC 意味着这个路径会传递给：
# logger_lib 自己编译时（处理 logger.cpp）
# 所有链接 logger_lib 的其他目标（如主程序）
target_include_directories(logger_lib PUBLIC libs/logger/)

# 创建可执行文件
add_executable(demo main.cpp)

# 链接所有库到可执行文件
target_link_libraries(demo
    PRIVATE
        math_lib
        string_lib
        logger_lib
)

# 设置 C++ 标准
set_property(TARGET math_lib PROPERTY CXX_STANDARD 17)
set_property(TARGET string_lib PROPERTY CXX_STANDARD 17)
set_property(TARGET logger_lib PROPERTY CXX_STANDARD 17)
set_property(TARGET demo PROPERTY CXX_STANDARD 17)

```
```c++
//main.cpp

#include <iostream>
#include "math_operations.h"
#include "string_utils.h"
#include "logger.h"

int main() {
    logger::info("Starting multi-library demo");

// 使用数学库
    std::cout << "\n=== Math Library Demo ===" << std::endl;
    int a = 15, b = 5;
    std::cout << a << " + " << b << " = " << math::add(a, b) << std::endl;
    std::cout << a << " * " << b << " = " << math::multiply(a, b) << std::endl;
    std::cout << "Average of " << a << " and " << b << " = " << math::average(a, b) << std::endl;

// 使用字符串库
    std::cout << "\n=== String Library Demo ===" << std::endl;
    std::string text = "Hello CMake";
    std::cout << "Original: " << text << std::endl;
    std::cout << "Upper: " << string_utils::toUpper(text) << std::endl;
    std::cout << "Lower: " << string_utils::toLower(text) << std::endl;
    std::cout << "Reversed: " << string_utils::reverse(text) << std::endl;

// 使用日志库
    std::cout << "\n=== Logger Library Demo ===" << std::endl;
    logger::info("This is an info message");
    logger::warning("This is a warning message");
    logger::error("This is an error message");

logger::info("Demo completed successfully");

return 0;
}
```

![](/media/202605/2026-05-15_225218_0039500.040848919497813885.png)
## 构建和运行

```bash
# 配置
cmake -S . -B build  -G "MinGW Makefiles"

# 构建
cmake --build build

# 运行
./build/demo              # Linux/macOS
build\Debug\demo.exe      # Windows
```

## REF
 ```
//创建库文件
add_library(<name> [STATIC | SHARED | MODULE | OBJECT | INTERFACE]
            [EXCLUDE_FROM_ALL]
            [源文件列表...])

//target_include_directories 是 CMake 中用于指定编译特定目标（target）时所需的头文件搜索路径的命令。
target_include_directories(<target> 
    <INTERFACE|PUBLIC|PRIVATE> 
    <目录1> <目录2> ...
)
```