Compiling with external libraries

I am having an issue with compiling one of the sample (example codes) for a C++ based jwt library from a github project: jwt-cpp I cloned it and compiled it using the steps provided in the README file, which seemed successful.

After that I did a ldconfig.

Now, I am trying to build the example code.

#include <iostream> #include "jwt/jwt_all.h" using json = nlohmann::json; int main() { // Setup a signer HS256Validator signer("secret!"); // Create the json payload that expires 01/01/2017 @ 12:00am (UTC) json payload = {{"sub", "subject"}, {"exp", 1483228800}}; // Let's encode the token to a string auto token = JWT::Encode(signer, payload); std::cout << token << std::endl; } 

I compile this with a command on terminal, which says:

g++ -std=c++11 \ -I/usr/local/include \ -I/usr/local/include \ /usr/local/lib/libjwt.a \ /usr/local/lib/libcrypto.a \ sign.cpp -o sign 

And it results in following error:

/tmp/ccX4ghoR.o: In function `main': sign.cpp:(.text+0x24e): undefined reference to JWT::Encode(MessageSigner const&, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long, unsigned long, double, std::allocator, nlohmann::adl_serializer> const&, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long, unsigned long, double, std::allocator, nlohmann::adl_serializer>)' /tmp/ccX4ghoR.o: In function `HS256Validator::HS256Validator(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)': sign.cpp:(.text._ZN14HS256ValidatorC2ERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE[_ZN14HS256ValidatorC5ERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE]+0x21): undefined reference to `EVP_sha256' sign.cpp:(.text._ZN14HS256ValidatorC2ERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE[_ZN14HS256ValidatorC5ERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE]+0x5f): undefined reference to `HMACValidator::HMACValidator(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, evp_md_st const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /tmp/ccX4ghoR.o: (.rodata._ZTV14HS256Validator[_ZTV14HS256Validator]+0x20): undefined reference to `HMACValidator::Verify(nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long, unsigned long, double, std::allocator, nlohmann::adl_serializer> const&, unsigned char const*, unsigned long, unsigned char const*, unsigned long) const' /tmp/ccX4ghoR.o: (.rodata._ZTV14HS256Validator[_ZTV14HS256Validator]+0x28): undefined reference to `HMACValidator::toJson[abi:cxx11]() const' /tmp/ccX4ghoR.o: (.rodata._ZTV14HS256Validator[_ZTV14HS256Validator]+0x38): undefined reference to `MessageValidator::Accepts(nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long, unsigned long, double, std::allocator, nlohmann::adl_serializer> const&) const' /tmp/ccX4ghoR.o: (.rodata._ZTV14HS256Validator[_ZTV14HS256Validator]+0x40): undefined reference to `HMACValidator::Sign(unsigned char const*, unsigned long, unsigned char*, unsigned long*) const' /tmp/ccX4ghoR.o: In function `HS256Validator::~HS256Validator()': sign.cpp: (.text._ZN14HS256ValidatorD2Ev[_ZN14HS256ValidatorD5Ev]+0x20): undefined reference to `HMACValidator::~HMACValidator()' /tmp/ccX4ghoR.o: (.rodata._ZTI14HS256Validator[_ZTI14HS256Validator]+0x10): undefined reference to `typeinfo for HMACValidator' collect2: error: ld returned 1 exit status 

What have I tried:

I have read through these questions to know what I might be doing wrong: How to use libraries and compile C file using external library from linux terminal, Although second question is specifically for C and not C++, the problem there and the solution is applicable to C++ as well.

I have also tried variants of command line compilation such as,

g++ -std=c++11 \ -I/usr/local/include \ -I/usr/local/include \ -L/usr/local/lib/ \ -lcrypto -ljwt \ sign.cpp -o sign 

I am familiar with the fact that when I do a -lfoo, the linker tries to find a libfoo.a at the location provided with -L option.

I have confirmed that the options that are used for compilation contains what they should.
For -I options: I can see jwt and openssl directories in /usr/local/include
For -L options: I can see libjwt.a, libssl.a, libcrypto.a, libssl.so, etc at /usr/local/lib/

Question: What am I doing wrong to compile this example?