Compiling with header files and templates in C++

Question

I'm trying to compile a file that includes a hpp file. The two functions declared in utility.hpp and implemented in utility.cpp use a template class to accept any type of input such that it's possible to call println(12) as well as println("test"). However, I'm struggling to compile it. If I compile it without using the hpp file it works fine, i.e. if I include directly the cpp file it works but if I include the hpp file as shown below it fails.

Command line (Ubuntu 18.04): g++ -o test test.cpp utility.cpp

Error obtained:

/tmp/ccl5rHBI.o: In function `main':
test.cpp:(.text+0x17): undefined reference to `void println<char const*>(char const*)'
collect2: error: ld returned 1 exit status

Files:

// test.cpp
#include "utility.hpp"

int main(int argc, char const *argv[])
{
    println("test");
    return 0;
}

// utility.hpp
#ifndef UTILITY_HPP_
#define UTILITY_HPP_

template<class T>
void print(T toPrint);

template<class T>
void println(T toPrint);

#endif

// utility.cpp
#include <iostream>
#include "utility.hpp"


template<class T>
void print(T toPrint){
    std::cout << toPrint;
}

template<class T>
void println(T toPrint){
    std::cout << toPrint << std::endl;
}

So my question is: How to fix it and compile those files such that the functions keep the property to accept any type of input.

Thanks in advance.

Compiling with header files and templates in C++

0 Answers0