This is probably due to my total inexperience with libraries.
Trying to include QSerialDevice as a static library.
Generated the library file libqserialdevice.a and put it in my project directory.
Added to my .pro

Qt Code: 
  1. INCLUDEPATH += C:\cpp\qt_projects\qtlogger\include
  2. LIBS += -L"C:\cpp\qt_projects\qtlogger\"  -llibqserialdevice.a
To copy to clipboard, switch view to plain text mode 

Builds ok, but doesn't look like the .exe file got any bigger. That worried me.
Then create a class to use the library functions in - SerialComm

Adding to SerialComm:

class AbstractSerial; // from the library

Causes build error: forward declaration of 'struct AbstractSerial'

Obviously not the right way. So what is?