Undefined reference using external library with CMake and Conan

问题

I am trying to develop a program that communicates with a PCSC USB reader using Conan and CMake with the LibLogicalAccess library. I followed the instructions of building and installing the library which seemed to have gone fine. I created a small simple console project with a "main.cpp" file. Following the C++ guide on the wiki of the library I tried to call a function from the library which resulted in a "Undefined reference to function. I know there are a lot of topics covering this but I have read as many as I could but could not seem to find the right solution.

I don't have much experience with Ubuntu/CMake/Conan/C++ so it might as well be a very simple fix.

OS: Kubuntu 18.04 Lang: C++ Related software: LibLogicalAccess 2.2.1, CMake 3.17.1, Conan 1.25.0

main.cpp

#include <iostream>

#include <logicalaccess/dynlibrary/librarymanager.hpp>
#include <logicalaccess/readerproviders/readerconfiguration.hpp>
#include <logicalaccess/cards/chip.hpp>

int main()
{
    std::cout << "Program started\n";

    // Reader configuration object to store reader provider and reader unit selection.
    std::shared_ptr<logicalaccess::ReaderConfiguration> readerConfig(new logicalaccess::ReaderConfiguration());

    // Set PCSC ReaderProvider by calling the Library Manager which will load the function from the corresponding plug-in
    readerConfig->setReaderProvider(logicalaccess::LibraryManager::getInstance()->getReaderProvider("PCSC"));

    std::cout << "after..\n";
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.16)

project(project)
include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup(TARGETS)
set(CMAKE_CXX_FLAGS "-I /usr/include/PCSC")
add_executable(project main.cpp)
target_link_libraries(project PUBLIC CONAN_PKG::LogicalAccess)

When I try to build the program using cmake --build . this is the output:

[100%] Linking CXX executable bin/project
CMakeFiles/project.dir/main.cpp.o: In function `main':
main.cpp:(.text+0x140): undefined reference to `logicalaccess::LibraryManager::getReaderProvider(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
collect2: error: ld returned 1 exit status
CMakeFiles/project.dir/build.make:191: recipe for target 'bin/project' failed
make[2]: *** [bin/project] Error 1
CMakeFiles/Makefile2:95: recipe for target 'CMakeFiles/project.dir/all' failed
make[1]: *** [CMakeFiles/project.dir/all] Error 2
Makefile:103: recipe for target 'all' failed
make: *** [all] Error 2

The weird part is that the first line of code: std::shared_ptr<logicalaccess::ReaderConfiguration> readerConfig(...) works fine and the second line of code gives an undefined reference.

I have tried other functions in the same file which give the same result. The file compiles and runs fine when I remove the last "setReaderProvider" line of code. Also tried a lot of different little adjustments regarding the conanfile.txt and CMakeLists.txt.

回答1:

Your error says:

main.cpp:(.text+0x140): undefined reference to `logicalaccess::LibraryManager::getReaderProvider(std::__cxx11::basic_string, std::allocator > const&)'

It occurs because your CMake is using libstdc++11 to link, however, Conan is configured to use libstdc++ due backward compatibility. You need to update your default libcxx:

conan profile update settings.compiler.libcxx=libstdc++11 default

Please, read this section in Conan docs How to Manage GCC ABI to get more information.

Also, it's explained on step 5 of Getting Started.

Now when building again, you will need that your local packages won't be available, because it's a new package, using different settings, so you will need to install, or build from sources. The link to libstdc++11 is automatically managed by Conan, it passes the definitions to CMake.

Regards!

来源：https://stackoverflow.com/questions/62004186/undefined-reference-using-external-library-with-cmake-and-conan

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