1st scenario.

I am having 4 library projects and one application project. Application project is using all the 4 library files.
The libraries are BasicSignalProcessing, ePIAF, FileIO, MainMixer and application is MainMixerTestApplication.

1. ePIAF library project has the reference(Project References) on BasicSignalProcessing.
2. FileIO library project has the reference(Project References) on BasicSignalProcessing and ePIAF library project.
3. MainMixer library project has the reference(Project References) on BasicSignalProcessing and ePIAF library project. 
4. MainMixerTestApplication application project has the reference(Project References) on BasicSignalProcessing, ePIAF, 
FileIO and MainMixer library projects.

Individual libraries are getting built properly but MainMixerTestApplication is failing with error 'undefined reference 
to ...'.
I have added the necessary include folders in search paths and I am linking the above libraries by including them in 
'Properties->QNX C/C++ Project->Linker->Extra library paths'

Attached the build log for your reference.

Can anyone tell me what is the exact reason and how to get rid of this CRITICAL error ?

2nd scenario.

I have created a TestLib library project and TestMain application project where main function calls the TestLibProc 
function implemented in the test library. In this also I am getting similar error even though I am including the library
 while linking and it is getting resolved only if I include the OBJ file(TestLib.o) in the linker(Same is not happening 
in the 1st example as it is flashing an error in both MainMixer & MainMixerTestApplication). I feel including OBJ file 
is a crude method.