simple module code cannot be linked in correctly

[Denrreau Hsing]

hi everyone

i am working on omnet++ 5.2.1,   ubuntu 16.04, and the compiler is g++. i tried creating a simple module, say A.  an error prompted when i used it  in network(the simplest case, just an object of A), it said " class A not found, perhaps its code not linked in...".  

i have tried some solutions on internet, including namespace tricks,  they did not work at all.  and i also checked the register class list by running the executable with "-h classes" option,  class A's presented in the list. so i reckon,  it must be the linking problem. but how to fix it is beyond me.

i will be very grateful if anyone responses.