Libraries loaded with Conan2.0 not linking with CPP Executable

Question

My project has:

1 cpp file
Conan2.0 as package manager
CMake The files are as follows:

conanfile.txt

[tool_requires]
cmake/3.27.1

[requires]
nlohmann_json/3.11.2
libcurl/8.2.1
openssl/3.1.2

[generators]
CMakeDeps
CMakeToolchain

CMakeLists.txt

cmake_minimum_required(VERSION 3.27.1)
project(Testing
        VERSION 1.0
        DESCRIPTION "Testing Application"
        LANGUAGES CXX)

set(CMAKE_VERBOSE_MAKEFILE ON)
set(CMAKE_SWIG_FLAGS "-Wall")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -v")

find_package(CURL REQUIRED) 
message(${CURL_INCLUDE_DIRS})
message(${CURL_LIBRARIES})

find_package(OpenSSL REQUIRED)
find_package(nlohmann_json REQUIRED)

include_directories(${CURL_INCLUDE_DIRS})
include_directories(${OpenSSL_INCLUDE_DIR})
include_directories(${nlohmann_json_INCLUDE_DIR})



add_executable(e_test encrypt_test.cpp )

target_link_libraries(e_test CURL::libcurl ${OpenSSL_LIBRARIES} nlohmann_json::nlohmann_json )

CPP File:

#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>
#include <openssl/err.h>

int main() {
    // Initialize the OpenSSL library
    OpenSSL_add_all_algorithms();
    ERR_load_crypto_strings();

    // Load the recipient's public key
    EVP_PKEY* publicKey = nullptr;
    FILE* publicKeyFile = fopen("../public_key.pem", "rb"); // Load the recipient's public key
    if (publicKeyFile) {
        publicKey = PEM_read_PUBKEY(publicKeyFile, nullptr, nullptr, nullptr);
        fclose(publicKeyFile);
    }
    else {
        std::cerr << "Error loading public key." << std::endl;
        return 1;
    }

    // Message to encrypt
    std::string message = "Hello, OpenSSL!";

    // Buffer for encrypted message
    unsigned char* encryptedMessage = nullptr;
    size_t encryptedMessageLength = 0;

    // Create an EVP context
    EVP_PKEY_CTX* ctx = EVP_PKEY_CTX_new(publicKey, nullptr);
    

    // Initialize the encryption operation
    if (EVP_PKEY_encrypt_init(ctx) == 1 &&
        EVP_PKEY_encrypt(ctx, nullptr, &encryptedMessageLength, reinterpret_cast<const unsigned char*>(message.c_str()), message.length()) == 1) {
            std::cout<<"I am here\n";
            encryptedMessage = new unsigned char[encryptedMessageLength];
        if (EVP_PKEY_encrypt(ctx, encryptedMessage, &encryptedMessageLength, reinterpret_cast<const unsigned char*>(message.c_str()), message.length()) != 1) {
            std::cerr << "Encryption error." << std::endl;
            return 1;
        }
    }

    // Print or process the encrypted message as needed
    std::cout << "Encrypted message length: " << encryptedMessageLength <<"\n"  ;
    std::cout << "Encrypted message: " << std::string(reinterpret_cast<const char*>(encryptedMessage), encryptedMessageLength) << std::endl;

    // Clean up
    delete[] encryptedMessage;
    EVP_PKEY_CTX_free(ctx);
    EVP_PKEY_free(publicKey);
    ERR_free_strings();

    return 0;
}

The error:

Undefined symbols for architecture x86_64:
  "_EVP_PKEY_CTX_free", referenced from:
      _main in encrypt_test.cpp.o
  "_EVP_PKEY_CTX_new", referenced from:
      _main in encrypt_test.cpp.o
  "_EVP_PKEY_encrypt", referenced from:
      _main in encrypt_test.cpp.o
  "_EVP_PKEY_encrypt_init", referenced from:
      _main in encrypt_test.cpp.o
  "_EVP_PKEY_free", referenced from:
      _main in encrypt_test.cpp.o
  "_OPENSSL_init_crypto", referenced from:
      _main in encrypt_test.cpp.o
  "_PEM_read_PUBKEY", referenced from:
      _main in encrypt_test.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

I am invoking the CMAKE in the following manner:

#!/bin/bash

conan profile detect

conan install . --output-folder=build --build=missing

cd build

sh conanrun.sh

cmake -G "Ninja" -DCMAKE_TOOLCHAIN_FILE=conan_toolchain.cmake -DCMAKE_BUILD_TYPE=Debug .. && cmake --build . --config Debug

sh deactivate_conanrun.sh

Note: Removing conanrun.sh and deactivating script doesn't make a difference.

When built using command line, this code runs flawlessly; this was also running fine when conan wasn't introduced. I have debugged if cmake is able to find the necessary library files and header files from conan build; and it is doing so. I am not sure what i am doing wrong here

Why ${OpenSSL_LIBRARIES} (which should be ${OPENSSL_LIBRARIES}) rather than linking to a target (OpenSSL::SSL OpenSSL::Crypto) as you have done with the other libraries? Note that your include_directories calls are unnecessary when lining to targets and they avoid issues with variable name typos — Alan Birtles
– Alan Birtles, Commented Sep 8, 2023 at 10:18
Hey @AlanBirtles we need the include_directories otherwise the headerfiles aren't found ( I tried that ). Also, even after linking OpenSSL::SSL OpenSSL::Crypto instead of ${OPENSSL_LIBRARIES} gave the same error. Also, OpenSSL_Libraries link to the same OPENSSL Libraries; I have checked it as well — Aditya Mukherjee
– Aditya Mukherjee, Commented Sep 8, 2023 at 10:44
sounds like there's something very wrong with your project if you have to manually specify include directories. How are you invoking cmake? — Alan Birtles
– Alan Birtles, Commented Sep 8, 2023 at 11:28
@AlanBirtles My requirement is, i have to run this code in a different device where the packages might not be preinstalled. So i am running conan to install the packages first and create this executable. So, i need to specify these libraries and headers explicitly. That's how the conan documentation asked me to do. But somehow i am doing it wrong!! — Aditya Mukherjee
– Aditya Mukherjee, Commented Sep 8, 2023 at 11:32
There's no include_directories in the documentation? How are you invoking cmake? — Alan Birtles
– Alan Birtles, Commented Sep 8, 2023 at 11:34

Adrian Mole · Accepted Answer · 2023-09-10 09:39:55Z

2

Debug Build didn't work for this cause; Following the documentation using the following solved the issue:

cmake .. -DCMAKE_TOOLCHAIN_FILE=conan_toolchain.cmake -DCMAKE_BUILD_TYPE=Release &&  cmake --build .

edited Sep 10, 2023 at 9:39

Adrian Mole

52.1k193 gold badges61 silver badges101 bronze badges

answered Sep 9, 2023 at 10:08

Aditya Mukherjee

495 bronze badges

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1 Comment

Alan Birtles Over a year ago

ah, yes you need to pass -s build_type=Debug to conan or create a debug profile docs.conan.io/2/tutorial/consuming_packages/…

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