Graphical Debugger Crashes

[samwalrus]

Using SWI-Prolog (Multi-threaded, 64 bits, Version 7.3.9) Ubuntu
When trying to graphically debug a program prolog crashes.
The query is:
?- gen_arcs(1,[0,1],T), maplist(sep,T,Arcs,_).

The error:
[trace] ?- gen_arcs(1,[0,1],T), maplist(sep,T,Arcs,_).
T = [t(arc(1, 0, 1), [1, 0, 1])],
Arcs = [arc(1, 0, 1)] ;
T = [t(arc(1, 1, 1), [1, 1, 1])],
Arcs = [arc(1, 1, 1)] ;
[Thread 1 (main) at Sat Oct 17 18:39:46 2015] pl-write.c:1040: writePrimitive: Assertion failed: 0
C-stack trace labeled "assert_fail":
[0] PL_strtod() at ??:? [0x7fc33e48d7f0]
[1] __assert_fail() at ??:? [0x7fc33e4522c1]
[2] destroyXR() at ??:? [0x7fc33e44d489]
[3] destroyXR() at ??:? [0x7fc33e44dc7b]
[4] destroyXR() at ??:? [0x7fc33e44e340]
[5] destroyXR() at ??:? [0x7fc33e44f250]
[6] utf8_strncmp() at ??:? [0x7fc33e486c01]
[7] PL_next_solution() at ??:? [0x7fc33e3e9145]
[8] PL_call_predicate() at ??:? [0x7fc33e3f23bc]
[9] pl_pce_init() at ??:? [0x7fc33c513b0d]
[10] pl_pce_init() at ??:? [0x7fc33c513b90]
[11] PL_next_solution() at ??:? [0x7fc33e3e917f]
[12] PL_call_predicate() at ??:? [0x7fc33e3f23bc]
[13] pl_pce_init() at ??:? [0x7fc33c513b0d]
[14] pl_pce_init() at ??:? [0x7fc33c513b90]
[15] PL_next_solution() at ??:? [0x7fc33e3e917f]
[16] pl_skip_list3_va() at ??:? [0x7fc33e425fa3]
[17] pl_skip_list3_va() at ??:? [0x7fc33e42615d]
[18] PL_next_solution() at ??:? [0x7fc33e3e9248]
[19] PL_interrupt() at ??:? [0x7fc33e4440c4]
[20] PL_interrupt() at ??:? [0x7fc33e443b63]
[21] PL_next_solution() at ??:? [0x7fc33e3f06e4]
[22] pl_skip_list3_va() at ??:? [0x7fc33e425b2e]
[23] pl_skip_list3_va() at ??:? [0x7fc33e4262b0]
[24] PL_toplevel() at ??:? [0x7fc33e3e314d]
[25] prolog(main+0x2d) [0x40083d]
[26] __libc_start_main() at /build/buildd/eglibc-2.19/csu/libc-start.c:321 [0x7fc33ddf5ec5]
[27] prolog(+0x881) [0x400881]
Aborted (core dumped)

The program is:

:-use_module(library(clpfd)).

fd_length(L, N) :-
   N #>= 0,
   fd_length(L, N, 0).

fd_length([], N, N0) :-
   N #= N0.
fd_length([_|L], N, N0) :-
   N1 is N0+1,
   N #>= N1,
   fd_length(L, N, N1).

equal_truth(X, Y, R) :- X == Y, !, R = true.
equal_truth(X, Y, R) :- ?=(X, Y), !, R = false. % syntactically different
equal_truth(X, Y, R) :- X \= Y, !, R = false. % semantically different
equal_truth(X, Y, R) :- R == true, !, X = Y.
equal_truth(X, X, true).
equal_truth(X, Y, false) :-
   dif(X, Y).

=(X, Y, T) :-
  equal_truth(X, Y, T).

if_( C_1, Then_0, Else_0) :-
   call(C_1, Truth),
   functor(Truth,_,0),  % safety check
   ( Truth == true -> Then_0 ; Truth == false, Else_0 ).

list_memberd_t([]    ,_,false).
list_memberd_t([Y|Ys],X,Truth) :-
   if_(X=Y, Truth=true, list_memberd_t(Ys,X,Truth)).

memberd_t(X,Xs,Truth) :- list_memberd_t(Xs,X,Truth).

list_memberd_truth(Xs,X,Truth) :- list_memberd_t(Xs,X,Truth).

gen_arcs(MaxNodes,Language,Arcs):-
    append([Min|_],[Max],Language),
    Arc_Label in Min..Max,
    Arcs=[t(arc(X,Arc_Label,Z),[X,Arc_Label,Z])],
    [X,Z] ins 1..MaxNodes,
    1 #= min(X,Z),
    label([X,Z]),
    label([Arc_Label]).

gen_arcs(Max_Nodes,Language,[t(arc(X,Arc_Label,Z),[X,Arc_Label,Z])|TArcs]):-
    append([Min|_],[Max],Language),
    Arc_Label in Min..Max,
    gen_arcs(Max_Nodes,Language,TArcs),
    maplist(sep,TArcs,Arcs,_),
    chain([EX,EZ,X,Z],#>=),
    label([Arc_Label]),
    [X,Z] ins 1..Max_Nodes,
    label([X,Z]),
    memberd_t(arc(X,Arc_Label,Z),Arcs,false),
    memberd_t(arc(EX,_,EZ),Arcs,true).

combined_arcs_vars(Combined,Arcs,Vars):-
    maplist(sep,Combined,Arcs,Vars).

sep(t(Arc,Var),Arc,Var).
sep2(arc(Node1,Edge,Node2),Node1,Edge,Node2).

[JanWielemaker]

The program contains syntax errors in at least two places and you give no clue how you
start the trace session. Without details I cannot reproduce this.

[samwalrus]

I don't know what the syntax errors are, prolog does does not give any errors when loading the file. I am trying to debug the program as I know it does not work.

I just load the file from the command line:
prolog -s 'my_file.pl'

Welcome to SWI-Prolog (Multi-threaded, 64 bits, Version 7.3.9)
Copyright (c) 1990-2015 University of Amsterdam, VU Amsterdam
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.

For help, use ?- help(Topic). or ?- apropos(Word).

?- gtrace.
% The graphical front-end will be used for subsequent tracing
true.

[trace] ?- gen_arcs(1,[0,1],T), maplist(sep,T,Arcs,_).
T = [t(arc(1, 0, 1), [1, 0, 1])],
Arcs = [arc(1, 0, 1)] ;
T = [t(arc(1, 1, 1), [1, 1, 1])],
Arcs = [arc(1, 1, 1)] ;
T = [t(arc(1, 1, 1), [1, 1, 1]), t(arc(1, 0, 1), [1, 0, 1])],
Arcs = [arc(1, 1, 1), arc(1, 0, 1)] ;
T = [t(arc(1, 0, 1), [1, 0, 1]), t(arc(1, 1, 1), [1, 1, 1])],
Arcs = [arc(1, 0, 1), arc(1, 1, 1)] ;

at this point the system hangs and I abort by pressing ctrl-c a I then try the goal again:

[trace] ?- gen_arcs(1,[0,1],T), maplist(sep,T,Arcs,_).
T = [t(arc(1, 0, 1), [1, 0, 1])],
Arcs = [arc(1, 0, 1)] ;
T = [t(arc(1, 1, 1), [1, 1, 1])],
Arcs = [arc(1, 1, 1)] ;
[Thread 1 (main) at Sun Oct 18 09:52:00 2015] pl-write.c:1040: writePrimitive: Assertion failed: 0
C-stack trace labeled "assert_fail":
[0] PL_strtod() at ??:? [0x7f9ca7a097f0]
[1] __assert_fail() at ??:? [0x7f9ca79ce2c1]
[2] destroyXR() at ??:? [0x7f9ca79c9489]
[3] destroyXR() at ??:? [0x7f9ca79c9c7b]
[4] destroyXR() at ??:? [0x7f9ca79ca340]
[5] destroyXR() at ??:? [0x7f9ca79cb250]
[6] utf8_strncmp() at ??:? [0x7f9ca7a02c01]
[7] PL_next_solution() at ??:? [0x7f9ca7965145]
[8] PL_call_predicate() at ??:? [0x7f9ca796e3bc]
[9] pl_pce_init() at ??:? [0x7f9ca5a8fb0d]
[10] pl_pce_init() at ??:? [0x7f9ca5a8fb90]
[11] PL_next_solution() at ??:? [0x7f9ca796517f]
[12] PL_call_predicate() at ??:? [0x7f9ca796e3bc]
[13] pl_pce_init() at ??:? [0x7f9ca5a8fb0d]
[14] pl_pce_init() at ??:? [0x7f9ca5a8fb90]
[15] PL_next_solution() at ??:? [0x7f9ca796517f]
[16] pl_skip_list3_va() at ??:? [0x7f9ca79a1fa3]
[17] pl_skip_list3_va() at ??:? [0x7f9ca79a215d]
[18] PL_next_solution() at ??:? [0x7f9ca7965248]
[19] PL_interrupt() at ??:? [0x7f9ca79c00c4]
[20] PL_interrupt() at ??:? [0x7f9ca79bfb63]
[21] PL_next_solution() at ??:? [0x7f9ca796c6e4]
[22] pl_skip_list3_va() at ??:? [0x7f9ca79a1b2e]
[23] pl_skip_list3_va() at ??:? [0x7f9ca79a22b0]
[24] PL_toplevel() at ??:? [0x7f9ca795f14d]
[25] prolog(main+0x2d) [0x40083d]
[26] __libc_start_main() at /build/buildd/eglibc-2.19/csu/libc-start.c:321 [0x7f9ca7371ec5]
[27] prolog(+0x881) [0x400881]
Aborted (core dumped)

[JanWielemaker]

Ah. It is GitHub's wiki syntax that breaks the program ... Added .... around it and now the program is readable and syntactically correct. The abort is a quite vital piece of the info. With
that it reproduces (at least one time) I'll have a look. The required interaction might make it a
little hard to track :(

[JanWielemaker]

Hmm. I found two bugs in the gui tracer, but I'm unsure whether or not this particular one is fixed. You may want to try the latest git version.