Undefined symbols for architecture x86_64 (curlpp) - c++

Question

In the project I'm working on, I'm trying to use the curlpp library to make a simple html GET request. I pass the cpp file to clang++ with the following options:
clang++ -std=c++11 -stdlib=libc++ -I /usr/local/Cellar url_test.cpp
I then get these errors:
Undefined symbols for architecture x86_64:
"curlpp::OptionBase::OptionBase(CURLoption)", referenced from:
curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::Option(CURLoption, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in url_test-541b93.o
"curlpp::OptionBase::~OptionBase()", referenced from:
curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::Option(CURLoption, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in url_test-541b93.o
curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::~Option() in url_test-541b93.o
"curlpp::UnsetOption::UnsetOption(char const*)", referenced from:
curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::updateMeToOption(curlpp::OptionBase const&) in url_test-541b93.o
curlpp::OptionTrait<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, (CURLoption)10002>::updateHandleToMe(curlpp::internal::CurlHandle*) const in url_test-541b93.o
curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::getValue() const in url_test-541b93.o
"curlpp::RuntimeError::~RuntimeError()", referenced from:
curlpp::UnsetOption::~UnsetOption() in url_test-541b93.o
"curlpp::libcurlRuntimeAssert(char const*, CURLcode)", referenced from:
void curlpp::internal::CurlHandle::option<void*>(CURLoption, void*) in url_test-541b93.o
"curlpp::Easy::perform()", referenced from:
_main in url_test-541b93.o
"curlpp::Easy::Easy()", referenced from:
_main in url_test-541b93.o
"curlpp::Easy::~Easy()", referenced from:
_main in url_test-541b93.o
"curlpp::Cleanup::Cleanup()", referenced from:
_main in url_test-541b93.o
"curlpp::Cleanup::~Cleanup()", referenced from:
_main in url_test-541b93.o
"curlpp::OptionBase::operator<(curlpp::OptionBase const&) const", referenced from:
vtable for curlpp::OptionTrait<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, (CURLoption)10002> in url_test-541b93.o
vtable for curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > in url_test-541b93.o
"typeinfo for curlpp::LogicError", referenced from:
GCC_except_table0 in url_test-541b93.o
"typeinfo for curlpp::OptionBase", referenced from:
curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::updateMeToOption(curlpp::OptionBase const&) in url_test-541b93.o
typeinfo for curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > in url_test-541b93.o
"typeinfo for curlpp::RuntimeError", referenced from:
GCC_except_table0 in url_test-541b93.o
typeinfo for curlpp::UnsetOption in url_test-541b93.o
"_curl_easy_setopt", referenced from:
void curlpp::internal::CurlHandle::option<void*>(CURLoption, void*) in url_test-541b93.o
ld: symbol(s) not found for architecture x86_64
which I think means that the compiler cannot find any of the curlpp libraries.
Here's the code I'm trying to run:
1 #include <string>
2 #include <sstream>
3 #include <iostream>
4 #include <curlpp/cURLpp.hpp>
5 #include <curlpp/Easy.hpp>
6 #include <curlpp/Options.hpp>
7 #include <fstream>
8
9 using namespace curlpp::options;
10
11 int main(int, char **)
12 {
13 try
14 {
15 curlpp::Cleanup testCleanup;
16 curlpp::Easy miRequest;
17 miRequest.setOpt<Url>("http://www.wikipedia.org");
18 miRequest.perform();
19 }
20 catch(curlpp::RuntimeError & e)
21 {
22 std::cout << e.what() << std::endl;
23 }
24 catch(curlpp::LogicError & e)
25 {
26 std::cout << e.what() << std::endl;
27 }
28
29 return 0;
30 }
I'm running macOS Sierra 10.12.4 with Xcode command line tools and homebrew installed. I homebrew'd the curlpp library. I know that someone else was able to compile this project on Ubuntu 16.04 using gcc, so I think the issue is to do with macOS.
I'm quite new to cpp, so any help would be greatly appreciated!

Answer 1

You have to tell the compiler which libraries to link with your executable. In your case, the issue is solved by adding options -lcurlpp -lcurl.
By the way, the path you provide is not correct since headers actually reside in /usr/local/Cellar/curlpp/[insert version here]/include. Anyways, this compiles fine without adding include search path for libraries installed via homebrew since it automatically creates symlinks in /usr/local/include, which is one of default places for a compiler to search.

Answer 2

Your problem is that you are not linking the library you use. Add the library and you should be good.