1:      1  1 CALL pred empty_command.main/2-0 (det) empty_command.m:13
mdb> echo on
Command echo enabled.
mdb> register --quiet
mdb> break p
 0: + stop  interface pred empty_command.p/2-0 (det)
mdb> continue
       2:      2  2 CALL pred empty_command.p/2-0 (det) empty_command.m:23 (empty_command.m:14)
mdb> finish
       9:      2  2 EXIT pred empty_command.p/2-0 (det) empty_command.m:23 (empty_command.m:14)
mdb> dd -d 3 -n 7
p(53, 53)
Valid? no
q(53, 53)
Valid? yes
r(53, 53)
Valid? 
s(53, 53)
Valid? yes
r(53, 53)
Valid? yes
Found incorrect contour:
q(53, 53)
r(53, 53)
s(53, 53)
p(53, 53)
Is this a bug? no
p(53, 53)
Valid? [no] 
q(53, 53)
Valid? [yes] 
r(53, 53)
Valid? [yes] 
s(53, 53)
Valid? [yes] 
Found incorrect contour:
q(53, 53)
r(53, 53)
s(53, 53)
p(53, 53)
Is this a bug? yes
       9:      2  2 EXIT pred empty_command.p/2-0 (det) empty_command.m:23 (empty_command.m:14)
mdb> continue
53