如何构建CMake库并让外部以命名空间形式引入头文件？

项目基础信息 #

我有一个CMake项目，目录结构如下：

├── CMakeLists.txt
├── conanfile.py
├── include
│   └── my_algorithm.h
├── src
│   └── my_algorithm.cpp
└── test_package
    ├── CMakeLists.txt
    ├── conanfile.py
    └── src
        └── example.cpp

test_package/src/example.cpp中的代码：

#include "my_algorithm.h"
#include <vector>
#include <string>

int main() {
    algorithm();
}

当前CMakeLists.txt配置：

cmake_minimum_required(VERSION 3.15)
project(my_foundation CXX)

add_library(my_foundation src/algorithm.cpp)
target_include_directories(my_foundation PUBLIC include)

set_target_properties(my_foundation PROPERTIES PUBLIC_HEADER "include/algorithm.h")
install(TARGETS my_foundation)

需求：让外部使用者能以#include "foundation/my_algorithm.h"的形式引入头文件，而非直接#include "my_algorithm.h"。

尝试过的两种方法（均失败） #

方法1：在include目录下新增子文件夹 #

修改后的目录结构：

+ CMakeLists.txt
+ include
  + my_foundation
    + my_algorithm.h

修改后的CMakeLists.txt：

add_library(my_foundation src/my_algorithm.cpp)
target_include_directories(my_foundation PUBLIC include)

set_target_properties(my_foundation PROPERTIES PUBLIC_HEADER "include/my_foundation/my_algorithm.h")

测试时外部仍只能用#include "my_algorithm.h"引入，#include "my_foundation/my_algorithm.h"无效。

方法2：仅为外部使用添加「命名空间」 #

修改后的CMakeLists.txt：

add_library(my_foundation src/my_algorithm.cpp)
#target_include_directories(my_foundation PUBLIC include)
target_include_directories(my_foundation PRIVATE include/my_foundation include)
target_include_directories(my_foundation INTERFACE include)

结果与方法1一致，无法实现目标。

补充信息 #

test_package的CMakeLists.txt配置：

cmake_minimum_required(VERSION 3.15)
project(PackageTest CXX)
find_package(my_foundation CONFIG REQUIRED)
add_executable(example src/example.cpp)
target_link_libraries(example my_foundation::my_foundation)

使用Conan2构建测试的命令：

conan install .
cmake --preset conan-release
cmake --build --preset conan-release

正确配置方案 #

要实现目标，核心是确保安装时头文件的目录结构与接口包含路径匹配，同时适配库内部的头文件引用逻辑。

步骤1：调整目录结构 #

将头文件放入include/foundation目录，结构如下：

├── include
│   └── foundation
│       └── my_algorithm.h

步骤2：适配库内部的头文件引用 #

如果src/my_algorithm.cpp中引用了头文件，需修改为：

#include "foundation/my_algorithm.h"

步骤3：修改CMakeLists.txt配置 #

cmake_minimum_required(VERSION 3.15)
project(my_foundation CXX)

add_library(my_foundation src/my_algorithm.cpp)

# 区分构建时与安装后的include路径，确保内外场景均可用
target_include_directories(my_foundation PUBLIC 
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
    $<INSTALL_INTERFACE:include>
)

# 保留头文件的目录结构
set_target_properties(my_foundation PROPERTIES 
    PUBLIC_HEADER "include/foundation/my_algorithm.h"
)

# 安装时按目录结构放置头文件，与外部引入路径对应
install(TARGETS my_foundation
    EXPORT my_foundationTargets
    LIBRARY DESTINATION lib
    ARCHIVE DESTINATION lib
    PUBLIC_HEADER DESTINATION include/foundation
)

# 导出配置，确保find_package能正确识别库
install(EXPORT my_foundationTargets
    FILE my_foundationTargets.cmake
    NAMESPACE my_foundation::
    DESTINATION lib/cmake/my_foundation
)

步骤4：调整测试代码 #

修改test_package/src/example.cpp：

#include "foundation/my_algorithm.h"
#include <vector>
#include <string>

int main() {
    algorithm();
}

关键说明 #

• BUILD_INTERFACE和INSTALL_INTERFACE分别适配本地构建和安装后的include路径，保证两种场景下路径逻辑一致。
• PUBLIC_HEADER DESTINATION include/foundation确保安装后头文件被放置到include/foundation目录，与外部引入路径完全匹配。
• 库内部代码必须使用带命名空间的头文件路径，避免编译错误。

内容的提问来源于stack exchange，提问作者whyuenacccc