Re: [Boost-users] Newbie Question - Errors if i want to compile using g++

From: Michael B. Edwin Rickert (panda_at_[hidden])
Date: 2005-07-20 22:33:23

mix_at_[hidden] wrote:
> Hi all,
> 
> I'm a newbie in c++ and in boost too, but i want to learn ;) I've
> installed boost via apt and also with "hand-compile" but it doesn't run
> anyway..
> 
> here my code:
> 
> --------------------
> #include <iostream>
> #include <boost/regex.hpp>
> 
> using namespace boost;
> using namespace std;
> 
> int main()
> {
>   const boost::regex e("PING\\s:\\S+");
>   cmatch match;
> 
>   if(boost::regex_match("PING :jgWEjg",match,e))
>   {
>     cout << "PONG :" << match[1];
>   }
> 
> return 0;
> }
> --------------------
> 
> then i want to compile it with ""g++ main.cc -o test"

This is your problem. The boost regex library is not a header only 
library like some of the others, so you must link against it! This is 
what causes "undefined reference to ____" errors - these are linker 
errors generated because it dosn't know where to find the implementation 
of this function.

The exact line used will depend on your system. On my windows box using 
MinGW I'd link against it like so:

g++ main.cc -o test -lboost_regex-mgw

Note that the -mgw postfix refers to MinGW, so obviously your milage 
will vary.