The command lines given to the linker and CC are not showing. You need the linker to be given a ".a" or ".o" that exports g_base_info_unref and g_free symbols. Looking at my "C:\perl512\site\lib\auto\Glib\Glib.dll", g_free is imported from a file called libglib-2.0-0.dll . Since it looks like your are building the XS GTK DLLs, you will need a .a since I assume you are dynamic linking to some GTK DLLs. Not static linking. I'm not sure your can build a static GTK for perl in a single XS DLL since XS Glib.dll and XS Gtk2.dll need to use to same GTK/Glib C code and the same C statics.