CMake生成错误的头文件包含路径，如何修正为预期路径？

你的liba和libb的CMake配置中，target_include_directories的BUILD_INTERFACE设置错误，直接指向了include/liba和include/libb，导致依赖项目的包含路径被设为这两个子目录；另外，顶层CMake中多余的CMAKE_PREFIX_PATH/CMAKE_MODULE_PATH配置可能引入了不必要的根目录路径。

1. 修正liba的CMakeLists.txt #

修改target_include_directories，区分内部和外部的包含路径：

add_library(${PROJ_BIN_NAME} STATIC)
# 对外公开include目录，让依赖项目能通过#include <liba/xxx.hpp>访问头文件
target_include_directories(${PROJ_BIN_NAME} 
    PUBLIC 
        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
        $<INSTALL_INTERFACE:include>
    # 内部源文件可直接用#include "xxx.hpp"引用头文件
    PRIVATE
        ${CMAKE_CURRENT_SOURCE_DIR}/include/liba
)

2. 修正libb的CMakeLists.txt #

同样调整target_include_directories：

add_library(${PROJ_BIN_NAME})
target_include_directories(${PROJ_BIN_NAME} 
    PUBLIC 
        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
        $<INSTALL_INTERFACE:include>
    PRIVATE
        ${CMAKE_CURRENT_SOURCE_DIR}/include/libb
)

3. 清理顶层CMakeLists.txt的多余配置 #

移除手动添加的CMAKE_PREFIX_PATH和CMAKE_MODULE_PATH，FetchContent_Declare的OVERRIDE_FIND_PACKAGE参数已能让CMake正确定位依赖：

cmake_minimum_required(VERSION 3.28)
project(TopLevel VERSION 1.0.0 LANGUAGES CXX)
set(CMAKE_VERBOSE_MAKEFILE TRUE)
cmake_policy(SET CMP0177 NEW)

include(FetchContent)

FetchContent_Declare(liba SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/liba" OVERRIDE_FIND_PACKAGE)
FetchContent_MakeAvailable(liba)

FetchContent_Declare(libb SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/libb" OVERRIDE_FIND_PACKAGE)
FetchContent_MakeAvailable(libb)

add_subdirectory(app)

4. 验证效果 #

修改完成后，依赖项目（如app）的包含路径会变为liba/include和libb/include。你可以在app中通过#include <liba/helpers.hpp>、#include <libb/test.hpp>正确引用头文件，同时liba和libb内部的源文件仍可使用#include "helpers.hpp"这类简洁的引用方式。

内容的提问来源于stack exchange，提问作者Phoenix