CMake add_subdirectory 与 find_package？

Question

我有以下项目/源结构:

MyProject
|-MyProject
| |-src
| | |-project.c
| |
| |-CMakeLists.txt
|
|-MyLibrary
  |-include
  | |-hello.h
  |
  |-src
  | |-hello.c
  |
  |-CMakeLists.txt

MyProject/src/project.c 包含 MyLibrary/include/hello.h，后者又包含来自系统的 libusb.h (使用 CMake 找到)。

我正在使用以下代码在 MyLibrary/CMakeLists.txt 中添加 libusb 依赖项:

# Find libusb
find_package(LibUsb REQUIRED)

# Include libusb
include_directories(${LIBUSB_INCLUDE_DIR})

# Add dependencies
target_link_libraries(owi535 ${LIBUSB_LIBRARY})

然而，在编译 MyProject(包括使用 add_subdirectory 和 target_link_libraries 的 MyLibrary)时，我得到一个错误说明libusb.h 找不到。

我可以自己编译 MyLibrary，但是编译 MyProject 需要 libusb.h 在它的包含路径中，而它不是.

有没有办法通过添加 MyLibrary 作为依赖项，MyProject 通过它拉动 libusb.h？这意味着我不需要为包含 MyLibrary 的每个项目重复 find_package 代码。

---

我遇到的另一个问题是相似的；当我编译 MyProject 时，在 MyLibrary 中调用 libusb 函数时出现错误，指出存在 Undefined symbols，但是在编译 MyLibrary 时 它自己，没有错误。

Undefined symbols for architecture x86_64:
  "_libusb_close", referenced from:
      _my_close_method in libMyLibrary.a(hello.c.o)
  "_libusb_exit", referenced from:
      _my_exit_method in libMyLibrary.a(hello.c.o)
  "_libusb_init", referenced from:
      _my_init_method in libMyLibrary.a(hello.c.o)
  "_libusb_open_device_with_vid_pid", referenced from:
      _my_open_method in libMyLibrary.a(hello.c.o)
ld: symbol(s) not found for architecture x86_64

Answer 1

来自cmake documentation :

PUBLIC and INTERFACE items will populate the INTERFACE_INCLUDE_DIRECTORIES property of <target>.

Targets may populate this property [INTERFACE_INCLUDE_DIRECTORIES] to publish the include directories required to compile against the headers for the target. Consuming targets can add entries to their own INCLUDE_DIRECTORIES property such as $<TARGET_PROPERTY:foo,INTERFACE_INCLUDE_DIRECTORIES> to use the include directories specified in the interface of foo.

因此，您需要在 MyLibrary/CMakeLists.txt 中使用它:

target_include_directories(MyLibrary PUBLIC ${LIBUSB_INCLUDE_DIR})