Cmake找到包，但无法链接它们。

Question

我试图编译一个需要导入两个外部库的CMake项目。这两个库的.so文件都位于"/usr/lib“和"/usr/include”中。我已经为他们两个创建了Find.cmake文件；下面是(FindECDSA.cmake)的一个示例：

find_path(ECDSA_INCLUDE_DIR NAMES ecdsa.h DOC "ECDSA-lib include directory")
find_library(ECDSA_LIBRARY NAMES ECDSA DOC "ECDSA-lib library")


include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(ECDSA
    REQUIRED_VARS ECDSA_INCLUDE_DIR ECDSA_LIBRARY)


if(ECDSA_FOUND AND NOT TARGET ECDSA::ECDSA)
    add_library(ECDSA::ECDSA UNKNOWN IMPORTED)
    set_target_properties(ECDSA::ECDSA PROPERTIES
        IMPORTED_LOCATION "${ECDSA_LIBRARY}"
        INTERFACE_INCLUDE_DIRECTORIES "${ECDSA_INCLUDE_DIR}")
endif()


mark_as_advanced(ECDSA_INCLUDE_DIR ECDSA_LIBRARY)
set(ECDSA_INCLUDE_DIRS ${ECDSA_INCLUDE_DIR})
set(ECDSA_LIBRARIES ${ECDSA_LIBRARY})

然后，在CMakeLists.txt中找到它们并以下列方式链接到目标：

cmake_minimum_required(VERSION 3.12)
project(GEONET VERSION 0.1)

set(CMAKE_CXX_STANDARD 11)

# project variables
set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
set(CMAKECONFIG_INSTALL_DIR "${CMAKE_INSTALL_LIBDIR}/cmake/its")


find_package(ECDSA REQUIRED)

find_package(v2xSe REQUIRED)

set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/bin)

add_executable(geonet
    application.cpp
    ...
)

target_link_libraries(geonet PUBLIC v2xSe::v2xSe ECDSA::ECDSA ...)
install(TARGETS geonet EXPORT ${PROJECT_NAME} DESTINATION ${CMAKE_INSTALL_BINDIR})

问题是，CMake发现库没有问题，但是在编译的链接阶段完全找不到引用。以下是错误：

CMakeFiles/geonet.dir/main.cpp.o: In function `main':
/src/src/main.cpp:181: undefined reference to `boost::log::v2s_mt_posix::core::set_filter(boost::log::v2s_mt_posix::filter const&)'
CMakeFiles/geonet.dir/ahd_connection.cpp.o: In function `AHDConnection::compute_hash_sha256(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
/src/src/ahd_connection.cpp:210: undefined reference to `ecdsa_sha256(void const*, unsigned int, unsigned char*)'
CMakeFiles/geonet.dir/ahd_connection.cpp.o: In function `AHDConnection::sign_with_hsm(unsigned char*)':
/src/src/ahd_connection.cpp:225: undefined reference to `v2xSe_createRtSign(unsigned short, TypeHash_t*, unsigned short*, TypeSignature_t*)'
CMakeFiles/geonet.dir/ahd_connection.cpp.o: In function `AHDConnection::compute_hash_sha256(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
/src/src/ahd_connection.cpp:210: undefined reference to `ecdsa_sha256(void const*, unsigned int, unsigned char*)'
/src/src/ahd_connection.cpp:210: undefined reference to `ecdsa_sha256(void const*, unsigned int, unsigned char*)'
CMakeFiles/geonet.dir/ahd_connection.cpp.o: In function `AHDConnection::verify_data(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
/src/src/ahd_connection.cpp:310: undefined reference to `ecdsa_verify_signature(int, ecdsa_point_t, unsigned char*, ecdsa_sig_t, int, void (*)(void*, int, int), void*)'
CMakeFiles/geonet.dir/ahd_connection.cpp.o: In function `AHDConnection::AHDConnection(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int const&)':
/src/src/ahd_connection.cpp:61: undefined reference to `v2xSe_generateRtEccKeyPair(unsigned short, unsigned char, unsigned short*, TypePublicKey_t*)'
/src/src/ahd_connection.cpp:83: undefined reference to `ecdsa_open()'
CMakeFiles/geonet.dir/ahd_connection.cpp.o: In function `AHDConnection::~AHDConnection()':
/src/src/ahd_connection.cpp:89: undefined reference to `ecdsa_close()'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/geonet.dir/build.make:472: bin/geonet] Error 1
make[1]: *** [CMakeFiles/Makefile2:116: CMakeFiles/geonet.dir/all] Error 2
make: *** [Makefile:150: all] Error 2

我做错了什么？

Answer 1

我终于解决了这个问题:一些导入的库恰好是C库，因此必须使用以下行导入它们：

extern "C" {
    #include "v2xSe.h"
    #include "ecdsa.h"
}

我发现它们可以用GCC编译，但不能用g++编译。