CMAKE 将动态库链接到模块，但未显示为 link 依赖项

Question

如果之前有人问过这个问题，请指出正确的方向。我有 lib1 和 mod2，它们必须 link 在一起。该项目分布在几个文件夹和几个 CMakeLists.txt 文件中。我使用的 cmake 命令是这样的：

cmake 文件 1（基本目录）：

# Set C/C++ compile and linking flags
set(GCC_COVERAGE_COMPILE_FLAGS "-fpic -Wno-as-needed")

set(GXX_COVERAGE_COMPILE_FLAGS "-std=c++11")

set(GXX_COVERAGE_LINK_FLAGS "-Wl,--no-undefined -Wno-as-needed")

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS} ${GXX_COVERAGE_COMPILE_FLAGS}")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS}")
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER__FLAGS} ${GCC_COVERAGE_LINK_FLAGS}")

cmake 文件 2（lib1 目录）：

pybind11_add_module(elka_comm__common
    SHARED
    pyelka_common.cpp
    elka.cpp
    elka_comm.cpp
)

set_target_properties(elka_comm__common PROPERTIES
    LIBRARY_OUTPUT_DIRECTORY ${ELKA_BINARY_DIR}/python
)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS} ${GXX_COVERAGE_COMPILE_FLAGS}")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS}")
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER__FLAGS} ${GCC_COVERAGE_LINK_FLAGS}")

add_dependencies(elka_comm__common msg_gen)

cmake 文件 3（mod2 目录）：

#FIXME ldd not showing elka_comm__common as a link dependency
#            -> CommPort undefined symbol upon module import
target_link_libraries(
  elka_comm__gnd_station
    PUBLIC
  elka_comm__common
)

set_target_properties(elka_comm__gnd_station PROPERTIES
    LIBRARY_OUTPUT_DIRECTORY ${ELKA_BINARY_DIR}/python
)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS} ${GXX_COVERAGE_COMPILE_FLAGS}")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS}")
set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER__FLAGS} ${GCC_COVERAGE_LINK_FLAGS}")

add_dependencies(elka_comm__gnd_station
    elka_comm__common
    msg_gen
)

我的一些步骤作为完整性检查是多余的（例如设置标志 w/CMAKE 变量）。

以下是ldd -r <path-to-mod2.so>/mod2.so的部分输出：

    linux-vdso.so.1 =>  (0x00007fff777fe000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fadfe690000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fadfe479000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fadfe0b0000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fadfddaa000)
    /lib64/ld-linux-x86-64.so.2 (0x000055f1e6b2c000)
undefined symbol: _ZTIN4elka8CommPortE  (build_elka_data_collection/python/elka_comm__gnd_station.so)

lib1 被称为 elka_comm__common.so，因此它应该在 ldd 中显示为库依赖项，对吗？

cmake/make 命令的部分输出：

[100%] Linking CXX shared module ../../../python/elka_comm__gnd_station.so
cd /home/Programs/elka/elka_data_collection/build_elka_data_collection/src/elka_comm/gnd_station && /opt/cmake-3.4.3-Linux-x86_64/bin/cmake -E cmake_link_script CMakeFiles/elka_comm__gnd_station.dir/link.txt --verbose=1
/usr/bin/c++  -fPIC  -fpic -Wno-as-needed -std=c++11 -fpic -Wno-as-needed -std=c++11 -g   -shared  -o ../../../python/elka_comm__gnd_station.so CMakeFiles/elka_comm__gnd_station.dir/pyelka_gnd_station.cpp.o CMakeFiles/elka_comm__gnd_station.dir/elka_devices.cpp.o `CMakeFiles/elka_comm__gnd_station.dir/inet_comm.cpp.o  -L/home/Programs/elka/elka_data_collection/build_elka_data_collection/src/elka_comm/common  -L/home/Programs/elka/elka_data_collection/build_elka_data_collection/src/elka_comm/gnd_station  -L/home/Programs/elka/elka_data_collection/build_elka_data_collection/python  -L/home/Programs/elka/elka_data_collection/python ../../../python/elka_comm__common.so -Wl,-rpath,/home/Programs/elka/elka_data_collection/build_elka_data_collection/src/elka_comm/common:/home/Programs/elka/elka_data_collection/build_elka_data_collection/src/elka_comm/gnd_station:/home/Programs/elka/elka_data_collection/build_elka_data_collection/python:/home/Programs/elka/elka_data_collection/python`

由此看来，在我看来 linking 是正确完成的。我最好的直觉是 cmake 生成的 link 命令中的排序是不正确的，但除了知道 link 命令对排序有特殊要求外，我无法证明这一点。

Answer 1

通过将 -Wl,--no-as-needed 添加到 CMAKE_CXX_FLAGS 来解决。请注意，添加到 CMAKE_SHARED_LINKER_FLAGS|CMAKE_MODULE_LINKER_FLAGS 不起作用，将 -Wno-as-needed 添加到 CMAKE_CXX_FLAGS.

也不起作用

不过，其他问题仍然存在。如果有人有经验 w/binding c++ 代码到 python pm 我。

CMAKE 将动态库链接到模块，但未显示为 link 依赖项

CMAKE Linking dynamic library to module, but not showing as link dependency

c++

cmake

linker

dynamic-linking

pybind11