You have linker errors because the compiled code calls functions that aren't in the compiled code nor in any of the libraries. It looks like they're in other parts of lem3edit.
Name all of the project's
.cpp files on the command line instead of just
lem3edit.cpp. Also add
-lSDL2_ttf as Kieran said.
This is not an ideal long-term solution because you'll build the entire project every time, which is uncommon for C and C++ projects. You would rather build only the
.cpp files that need to be rebuilt, then link everything. In the long term, it would be nice if Kieran provided a Makefile, CMake files, have another build system, or at least give build instructions.
-Ipath adds
path for header lookup during compilation.
-Lpath adds
path for library lookup during subsequent
-l agruments.
-lmylib links to
libmylib.
-- Simon