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lalr: show lookback for debug

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* src/lalr.c (lookback_print): New.
(build_relations): Use it.
Also show edges.
This commit is contained in:
Akim Demaille
2019-03-01 06:16:46 +01:00
parent a8558bc5a6
commit 6d4e6bf118
1 changed files with 73 additions and 1 deletions
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74
src/lalr.c
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@@ -73,6 +73,10 @@ size_t nLA;
static goto_number **includes;
/* "(q, A → ω) lookback (p, A)" iff state p reaches state q on label ω.
Definition p.621 [DeRemer 1982]. */
static goto_list **lookback;
static void
@@ -239,6 +243,58 @@ initialize_goto_follows (void)
}
/* Find the state which LOOKBACK[LOOKBACK_INDEX] is about. */
static const state *
lookback_find_state (int lookback_index)
{
state *res = NULL;
for (int j = 0; j < nstates; ++j)
if (states[j]->reductions
&& states[j]->reductions->lookahead_tokens)
{
if (states[j]->reductions->lookahead_tokens - LA > lookback_index)
/* Went too far. */
break;
else
res = states[j];
}
/* Pacify "potential null pointer dereference" warning. */
if (!res)
abort ();
return res;
}
/* Print LOOKBACK for debugging. */
static void
lookback_print (FILE *out)
{
fputs ("lookback:\n", out);
for (int i = 0; i < nLA; ++i)
if (lookback[i])
{
fprintf (out, " %3d = ", i);
const state *s = lookback_find_state (i);
int rnum = i - (s->reductions->lookahead_tokens - LA);
const rule *r = s->reductions->rules[rnum];
fprintf (out, "(%3d, ", s->number);
rule_print (r, NULL, out);
fputs (") ->", out);
for (goto_list *sp = lookback[i]; sp; sp = sp->next)
{
fputc (' ', out);
goto_print (sp->value, out);
}
fputc ('\n', out);
}
fputc ('\n', out);
}
/* Add (S, R) -> GOTONO to LOOKBACK.
"(q, A → ω) lookback (p, A)" iff state p reaches state q on label ω.
The goto number GOTONO, whose source is S (which is
inconsistent), */
static void
add_lookback_edge (state *s, rule const *r, goto_number gotono)
{
@@ -284,6 +340,7 @@ build_relations (void)
path[length++] = s->number;
}
/* S is the end of PATH. */
if (!s->consistent)
add_lookback_edge (s, r, i);
@@ -313,6 +370,18 @@ build_relations (void)
}
}
if (trace_flag & trace_automaton)
{
goto_print (i, stderr);
fputs (" edges = ", stderr);
for (int j = 0; j < nedges; ++j)
{
fputc (' ', stderr);
goto_print (edge[j], stderr);
}
fputc ('\n', stderr);
}
if (nedges == 0)
includes[i] = NULL;
else
@@ -329,7 +398,10 @@ build_relations (void)
relation_transpose (&includes, ngotos);
if (trace_flag & trace_automaton)
relation_print ("includes", includes, ngotos, goto_print, stderr);
{
lookback_print (stderr);
relation_print ("includes", includes, ngotos, goto_print, stderr);
}
}
/* Compute FOLLOWS from INCLUDES, and free INCLUDES. */