如何创建依赖于外部头文件的cmake仅头文件库？ [英] How to create a cmake header-only library that depends on external header files?

问题描述

我有一个具有以下文件结构的项目：

I have a project with the following file structure:

project
 |
 |-------> lib1
 |           |----> lib1.h
 |
 |-------> lib2
 |           |----> lib2.h
 |
 |-------> main.cc

两个库 lib1 和 lib2 仅包含头文件，而 lib2.h 包括 lib1.h 和 main.cc 包括 lib2.h 。

The two libs lib1 and lib2 only contain header files while lib2.h includes lib1.h, and main.cc includes lib2.h.

现在如何为该项目编写cmake文件？我试图为<$ c创建一个接口库 $ c> lib2 ，但编译器找不到 lib1.h 。这是我的cmake文件的内容：

How do I write the cmake file for this project now? I tried to create an interface library for lib2, but the compiler can't find lib1.h. Here are the contents of my cmake files:

用于lib2的CMakeLists.txt：

add_library(lib2 INTERFACE)
target_sources(lib2 INTERFACE lib2.h)
target_include_directories(lib2 INTERFACE ../lib1/lib1.h)

CMakeLists.txt整个项目：

add_executable(project main.cc)
target_link_libraries(project lib2)

cmake文件中出了什么问题？

What's the problem in the cmake files?

推荐答案

如注释中所述，<$ c应该为$ c> target_include_directories 提供目录的路径，而不是文件的路径。

As stated in the comments, target_include_directories should be given a path to a directory, not to a file.

此外，如果要创建依赖关系 lib1 上的 lib2 ，您应该通过 target_link_libraries 进行操作：依赖关系不仅与包含目录有关，而且与编译选项，定义，目标属性有关……

Moreover, if you want to create a dependency for lib2 on lib1, you should do it through target_link_libraries: a dependency is not only about include directories, but also about compile options, definitions, target properties...

t arget_sources 不适用于接口库。通过此答案，您可以使用不带命令的自定义目标，而无需使用命令将源与目标关联，而不会影响构建过程（对于msvc，QtCreator和其他基于GUI的工具，这使得可通过IDE来访问源； AFAIK对其他构建工具无用）。

target_sources doesn't work with interface libraries. From this answer, You can use a custom target without commands to associate the sources to a target without impacting the build process (for msvc, QtCreator and other GUI-based tools, this makes the sources accessible through the IDE; AFAIK it's useless for other build tools).

您的cmake可能如下所示：

Your cmake may look like this:

add_library(lib1 INTERFACE)
target_sources(lib1 INTERFACE lib1.h)

target_include_directories(lib1 INTERFACE
    "${PROJECT_SOURCE_DIR}/lib1"
)

add_library(lib2 INTERFACE)
if(MSVC)
    add_custom_target(lib2.headers SOURCES lib2.h)
endif()

target_include_directories(lib2 INTERFACE
    "${PROJECT_SOURCE_DIR}/lib2"
)

target_link_libraries(lib2 INTERFACE lib1)

add_executable(project main.cc)
target_link_libraries(project lib2)

高级提示：您可以指定在 target_include_directories 中为构建树和安装树指定一个不同的目录（请参见文档）：

Advanced tip: you can specify a different directory in target_include_directories for the build tree and the install tree (see documentation):

target_include_directories(lib1 INTERFACE
    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/lib1>
    $<INSTALL_INTERFACE:${YOUR_INSTALL_DIR}/lib1>
)

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