determining the object files...

hello,
is there a utility to determine which object files are used to create a binary executable file?let me explain, please:
for ex. there are three files:
a.o b.o c.o
and these files are used to create a binary called:
prg
namely, a.o b.o c.o -> prg
so, how can i determine these three object files by investigating the binary file,prg ?

IF the files use distinctive names for functions and the executable (prg) is not stripped
then try nm.

nm prg > prg.dat
for file in *.o
do
   nm $file > $file.dat
done

Then you have to read thru the .dat files - this is not guranteed to work by any means.
Do you not have source code?