CMake：在构建过程中链接库？

Question

我是 CMake 新手，我正在尝试链接同一项目中生成的库。 （简化的）项目结构如下所示：

MyProject
├── CMakeLists.txt
├── Library1
│   └── CMakeLists.txt
│   └── include
│       └── foo.h
│       └── bar.h
│   └── src
│       └── foo.cpp
│       └── bar.cpp
├── Library2
│   └── CMakeLists.txt
│   └── include
│       └── baz.h
│   └── src
│       └── baz.cpp

CMakeLists.txt：

cmake_minimum_required (VERSION 3.17.0)
project(MyProject)

option(BUILD_SHARED_LIBS ON)

add_subdirectory(Library1)
add_subdirectory(Library2)

Library1/CMakeLists.txt：

project(Library1)

add_library(library1 
    src/foo.cpp 
    src/bar.cpp
)

target_include_directories(library1 PUBLIC
    ${CMAKE_SOURCE_DIR}/Library1/include
)

Library2/CMakeLists.txt：

project(Library2)

add_library(library2 
    src/baz.cpp
)

target_include_directories(library2 PUBLIC
    ${CMAKE_SOURCE_DIR}/Library1/include
    ${CMAKE_SOURCE_DIR}/Library2/include
)

find_library(LIB1 library1 HINTS ${CMAKE_SOURCE_DIR}/Library1)

target_link_libraries(library2 PUBLIC LIB1)

如果我跑步

cmake MyProject

我会收到此错误：

CMake Error: The following variables are used in this project, but they are set to NOTFOUND. 
LIB1 
    linked by target 'library1' in directory 'MyProject/Library1'

--- Generating done
CMake Generate step failed. Build files cannot be regenerated correctly.

当

library2

目标要在

library1

之后才会生成时，如何将

library1

链接到

cmake --build MyProject

？或者这不是构建该项目的正确方法？

Answer 1

此代码是错误的。

find_library(LIB1 library1 HINTS ${CMAKE_SOURCE_DIR}/Library1)

target_link_libraries(library2 PUBLIC LIB1)

在您展示的项目中，您不需要

find

任何库。它已经是您构建的一部分。

要解决您的问题，只需链接库即可：

target_link_libraries(library2 PUBLIC library1)

TLDR 关于何时使用

find_*

命令的解释：

CMake 提供了许多

find_*

命令，在使用已在计算机上安装

pre-built

二进制文件的包管理器、SDK 等时非常有用。

在这种情况下不需要它，因为

library1

已经是您项目的一部分。为什么 CMake 需要

find

它创建/定义的东西？