One of the most popular tools to debug C code is gdb. The
issue with gdb is that it cannot work with programs written
in Scheme and most of Lepton tools are such programs. This is easily
solvable. Instead of the call
gdb lepton-schematic
use
gdb --args guile -s /usr/local/bin/lepton-schematic
because this is the very command which is used internally in the
lepton-schematic script. Please note using of the full path
to the script here.