cdb is a machine-independent debugger for C programs compiled by lcc 4.x, a retargetable compiler for Standard C. The original version of cdb is described in the paper

D. R. Hanson and M. Raghavachari, A Machine-Independent Debugger, Software—Practice and Experience 26 (11), 1277-1299, Nov. 1996. PDF.

The latest version, 3.1, is described in

D. R. Hanson, A Machine-Independent Debugger—Revisited, Software—Practice and Experience 29 (10), 849-862, Aug. 1999. PDF.