from the manual
""--debug When this option is used the compiler will generate debug information. The debug information collected
in a file with .cdb extension can be used with the SDCDB. For more information see documentation
for SDCDB. Another file with no extension contains debug information in AOMF or AOMF51
format which is commonly used by third party tools."

the following
c:toolsSDCCbinSDCC -c --debug a.c
c:toolsSDCCbinSDCC -c --debug b.c
c:toolsSDCCbinSDCC -c --debug main.c
c:toolsSDCCbinSDCC --debug main.rel a.rel b.rel

generates an 8kb .ihx file and an empty file without extension

I REALLY need the .OMF (the file without extension)

in advance, thanks

Erik