Shared library not linking / cannot be done this way? - c++

Question

Here's my issue:
In my project, I have a class called Match. Now, I would like to use somebody else's code to compare their results. They, unfortunately, also have a class called Match.
OK, so I thought I'd do:
namespace MonteCarlo {
#include "monte-carlo/match.hpp"
}
I appreciate that this is not best practice, but I really just want to test the output for now rather than rewrite everything in new namespaces.
Then, I made a shared library out of his code, and linked it:
LIBPATHS = -L mysql_connector/lib/ -Lmonte-carlo/lib
LIBS = -l mysqlcppconn -l boost_date_time -l boost_iostream boost_system -l boost_filesystem -l MonteCarloTennis
But when I build, I get:
evaluator.cc:139: undefined reference to `MonteCarlo::Match::Match(double, double, double, double, bool, bool)'
evaluator.cc:140: undefined reference to `MonteCarlo::Match::play_match()'
But in the library, using nm, I see:
0000000000001286 T Match::Match(double, double, double, double, bool, bool)
0000000000001286 T Match::Match(double, double, double, double, bool, bool)
I am really new to libraries, so I could really use your advice. Am I getting this linker error because my library is not linking correctly, or because I wrapped the Match class in the namespace and thus the two functions in the library are not found?

Answer 1

Thank you to Joachim Pileborg for providing the answer!
Wrapping the #include in a namespace meant the linker couldn't find the corresponding function in the library. I have now fixed the issue by putting my colleague's code into namespaces.
So a very simple error, but there was so much that could have gone wrong (my first time building a library!) that it was really helpful to get Joachim's advice. Thanks again!