C++ 在CMAKE中使用具有静态依赖项的库

CMake中有没有一种方法可以将库用于具有不同静态依赖关系的多个目标？ 为了更好地解释它，请考虑这个最小的例子：我想要两个可执行文件：第一个应该打印“是”，第二个应该打印“否”。为此，我使用图书馆的“printsh”，它打印“something”。它打印的字符串来自“用户”（printyes或printno）提供的头文件。这看起来是这样的：

├── apps
│   ├── printno
│   │   ├── CMakeLists.txt
│   │   │       add_executable(printno main.cpp)
│   │   │       target_link_libraries(printno PRIVATE printsth)
│   │   │
│   │   ├── main.cpp
│   │   │       #include "printsth/printsth.h"
│   │   │       
│   │   │       int main() {
│   │   │         printsth();
│   │   │         return 0;
│   │   │       }
│   │   │
│   │   └── print_usr.h
│   │           #define USR_STRING  "NO"
│   │
│   └── printyes
│   │   ├── CMakeLists.txt
│   │   │       add_executable(printyes main.cpp)
│   │   │       target_link_libraries(printyes PRIVATE printsth)
│   │   │
│   │   ├── main.cpp
│   │   │       #include "printsth/printsth.h"
│   │   │       
│   │   │       int main() {
│   │   │         printsth();
│   │   │         return 0;
│   │   │       }
│   │   │
│   │   └── print_usr.h
│   │           #define USR_STRING  "YES"
│   │
├── extern
│   └── printsh
│       ├── include
│       │   └── printsh
│       │       └── printsh.h
│       │               void printsth();
│       │
│       ├── src
│       │    ├── CMakeLists.txt
│       │    │       add_library(printsth printsth.cpp)
│       │    │       target_include_directories(printsth PUBLIC ../include)
│       │    │
│       │    └── printsh.cpp
│       │            #include "printsth/printsth.h"
│       │            #include "print_usr.h"
│       │            #include <iostream>
│       │            
│       │            void printsth() {
│       │              std::cout << USR_STRING << std::endl;
│       │            }
│       │     
│       └── CMakeLists.txt
│               cmake_minimum_required(VERSION 3.11...3.16)
│               
│               project(printsh
│                   VERSION 0.1
│                   DESCRIPTION "Print something"
│                   LANGUAGES CXX)
│               
│               add_subdirectory(src)
│        
└── CMakeLists.txt
        cmake_minimum_required(VERSION 3.11...3.16)

        project(printexamples
            VERSION 0.1
            DESCRIPTION "Print examples"
            LANGUAGES CXX)

        add_subdirectory(apps/printyes)
        add_subdirectory(apps/printno)
        add_subdirectory(extern/printsth)

那么，我能告诉CMake在为printno构建printsh lib时使用apps/printno作为include目录，在为printyes构建printsh lib时使用apps/printyes作为include目录吗

---

我知道这个例子没有多大意义，可以很容易地去掉标题依赖项（例如，将自定义字符串作为参数传递给printsh（）），并且一切都很好。因此，这只是一个演示“现实世界”问题的示例，我无法轻松摆脱依赖关系。

在CMake意义上，库目标表示一次编译的库，但可以链接到多个目标（可执行库或其他库）

由于无法将两个宏定义编译到单个库中，因此需要为每个定义集创建不同的库目标。也就是说，您需要创建两个库

对于重复的命令序列，CMake提供宏和函数，并使用不同的参数多次调用它们

您还可以创建一个“参数化的”

CMakeLists.txt

，并（通过

add_子目录

）多次“调用”它：

extern/printsh/src/CMakeLists.txt：

# Requires 'printsth_target' and 'printish_usr_dir' variables to be set.
# The first variable denotes name of the target created,
# the second variable denotes include directory with 'print_usr.h' header.
if (NOT printsth_target)
  message(FATAL_ERROR "printsth_target variable is required but is not set.")
endif()
if (NOT printish_usr_dir)
  message(FATAL_ERROR "printish_usr_dir variable is required but is not set.")
endif()

# Create a library target with user-provided name
add_library(${printsth_target} printsth.cpp)
target_include_directories(${printsth_target} PUBLIC ../include)
# Add user-provided include directory
target_include_directories(${printsth_target} PRIVATE ${printish_usr_dir})

add_executable(printno main.cpp)
# Instantiate 'printsth' library with needed parameters.
set(printsth_target "printsh_no")
set(printish_usr_dir ${CMAKE_CURRENT_SOURCE_DIR})
# Need to specify the second argument - build directory, where the library will be built.
add_subdirectory(../../extern/printsh printsh_no_dir)
# No we can link with a library. Use a name, specified for 'printsth_target' variable.
target_link_libraries(printno PRIVATE printsh_no)

# <...>

add_subdirectory(apps/printyes)
add_subdirectory(apps/printno)
# Uncommenting the following line causes FATAL_ERROR triggered.
#add_subdirectory(extern/printsth)

使用这种脚本，

printsh

库可以在应用程序的

CMakeLists.txt

中实例化

apps/printno/CMakeLists.txt：

# Requires 'printsth_target' and 'printish_usr_dir' variables to be set.
# The first variable denotes name of the target created,
# the second variable denotes include directory with 'print_usr.h' header.
if (NOT printsth_target)
  message(FATAL_ERROR "printsth_target variable is required but is not set.")
endif()
if (NOT printish_usr_dir)
  message(FATAL_ERROR "printish_usr_dir variable is required but is not set.")
endif()

# Create a library target with user-provided name
add_library(${printsth_target} printsth.cpp)
target_include_directories(${printsth_target} PUBLIC ../include)
# Add user-provided include directory
target_include_directories(${printsth_target} PRIVATE ${printish_usr_dir})

add_executable(printno main.cpp)
# Instantiate 'printsth' library with needed parameters.
set(printsth_target "printsh_no")
set(printish_usr_dir ${CMAKE_CURRENT_SOURCE_DIR})
# Need to specify the second argument - build directory, where the library will be built.
add_subdirectory(../../extern/printsh printsh_no_dir)
# No we can link with a library. Use a name, specified for 'printsth_target' variable.
target_link_libraries(printno PRIVATE printsh_no)

# <...>

add_subdirectory(apps/printyes)
add_subdirectory(apps/printno)
# Uncommenting the following line causes FATAL_ERROR triggered.
#add_subdirectory(extern/printsth)

应修改顶层

CMakeLists.txt

，以便不实例化库

CMakeLists.txt：

# Requires 'printsth_target' and 'printish_usr_dir' variables to be set.
# The first variable denotes name of the target created,
# the second variable denotes include directory with 'print_usr.h' header.
if (NOT printsth_target)
  message(FATAL_ERROR "printsth_target variable is required but is not set.")
endif()
if (NOT printish_usr_dir)
  message(FATAL_ERROR "printish_usr_dir variable is required but is not set.")
endif()

# Create a library target with user-provided name
add_library(${printsth_target} printsth.cpp)
target_include_directories(${printsth_target} PUBLIC ../include)
# Add user-provided include directory
target_include_directories(${printsth_target} PRIVATE ${printish_usr_dir})

add_executable(printno main.cpp)
# Instantiate 'printsth' library with needed parameters.
set(printsth_target "printsh_no")
set(printish_usr_dir ${CMAKE_CURRENT_SOURCE_DIR})
# Need to specify the second argument - build directory, where the library will be built.
add_subdirectory(../../extern/printsh printsh_no_dir)
# No we can link with a library. Use a name, specified for 'printsth_target' variable.
target_link_libraries(printno PRIVATE printsh_no)

# <...>

add_subdirectory(apps/printyes)
add_subdirectory(apps/printno)
# Uncommenting the following line causes FATAL_ERROR triggered.
#add_subdirectory(extern/printsth)

#
添加子目录（apps/printyes）
添加子目录（apps/printno）
#取消对以下行的注释会触发致命的\u错误。
#添加子目录（extern/printsth）

您的意思是像cmake中的if else这样的东西吗？库不是“为…而构建”的，它只是构建一次，然后与其他模块链接在一起。CMake不会改变库的工作方式。欢迎使用堆栈溢出！这是一个很棒的第一个问题！要做到这一点，除了完全重新设计以删除依赖项之外，还有一种方法是创建

printsh

库的“是”和“否”版本。然后，将库的正确“是”或“否”版本链接到

printyes

和

printno

。谢谢您的评论。我看到它实际上不是一个真正的静态库@squareskittles问题是，在“现实”中，这可能是相当多的不同版本，我想保持libraray（printsh）独立于配置。另一种方法是将库源直接包含到可执行文件中，但我看不到任何方法仍然能够控制库源文件的导入路径等。感谢您的详细回答！这正是我要找的。我唯一没有真正了解的部分是add_subdirectory（）的作用以及为什么它是必需的（如果我构建了一个标准的、非参数化的libraray，我不必使用add_subdirectory（））。在原始代码中，您在根

CMakeLists.txt

中使用

add_subdirectory（extern/printsh）

来实例化（构建）库。在我的变体中，

apps/printno/CMakeLists.txt

和

apps/printyes/CMakeLists.txt

中有两个这样的调用（后一个文件与前一个文件类似，因此未显示）。