From: Akim Demaille <akim@epita.fr>
Date: Tue, 30 Jul 2002 11:06:50 +0000 (+0000)
Subject: Report rules which are never reduced by the parser: those hidden
X-Git-Tag: BISON-1_49b~62
X-Git-Url: https://git.saurik.com/bison.git/commitdiff_plain/e8832397ea06de8049828011aff948b5302ffe66
Report rules which are never reduced by the parser: those hidden
by conflicts.
* src/LR0.c (save_reductions): Don't make the final state too
different: save its reduction (accept) instead of having a state
without any action (no shift or goto, no reduce).
Note: the final state is now a ``regular'' state, i.e., the
parsers now contain `reduce 0' as default reduction.
Nevertheless, since they decide to `accept' when yystate =
final_state, they still will not reduce rule 0.
* src/print.c (print_actions, print_reduction): Adjust.
* src/output.c (action_row): Track reduced rules.
(token_actions): Report rules never reduced.
* tests/conflicts.at, tests/regression.at: Adjust.
---
diff --git a/ChangeLog b/ChangeLog
index 3c4a350f..ccb65060 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,20 @@
+2002-07-30 Akim Demaille <akim@epita.fr>
+
+ Report rules which are never reduced by the parser: those hidden
+ by conflicts.
+
+ * src/LR0.c (save_reductions): Don't make the final state too
+ different: save its reduction (accept) instead of having a state
+ without any action (no shift or goto, no reduce).
+ Note: the final state is now a ``regular'' state, i.e., the
+ parsers now contain `reduce 0' as default reduction.
+ Nevertheless, since they decide to `accept' when yystate =
+ final_state, they still will not reduce rule 0.
+ * src/print.c (print_actions, print_reduction): Adjust.
+ * src/output.c (action_row): Track reduced rules.
+ (token_actions): Report rules never reduced.
+ * tests/conflicts.at, tests/regression.at: Adjust.
+
2002-07-30 Akim Demaille <akim@epita.fr>
`stage' was accidently included in a previous patch.
diff --git a/NEWS b/NEWS
index 144d865d..6123e57a 100644
--- a/NEWS
+++ b/NEWS
@@ -8,7 +8,7 @@ Changes in version 1.49b:
%glr-parser
causes Bison to produce a Generalized LR (GLR) parser, capable of handling
almost any context-free grammar, ambiguous or not. The new declarations
- %dprec and %merge on grammar rules allow parse-time resolution of
+ %dprec and %merge on grammar rules allow parse-time resolution of
ambiguities. Contributed by Paul Hilfinger.
* Output Directory
@@ -58,6 +58,10 @@ Changes in version 1.49b:
* Useless rules, useless nonterminals
They are now reported, as a warning, with their locations.
+* Rules never reduced
+ Rules that can never be reduced because of conflicts are now
+ reported.
+
* Incorrect `Token not used'
On a grammar such as
diff --git a/src/LR0.c b/src/LR0.c
index 00ff736c..184a25f4 100644
--- a/src/LR0.c
+++ b/src/LR0.c
@@ -282,11 +282,6 @@ save_reductions (state_t *state)
int count = 0;
int i;
- /* If this is the final state, we want it to have no reductions at
- all, although it has one for `START_SYMBOL $end .'. */
- if (final_state && state->number == final_state->number)
- return;
-
/* Find and count the active items that represent ends of rules. */
for (i = 0; i < nritemset; ++i)
{
diff --git a/src/output.c b/src/output.c
index 1ec4d6b0..5f0fa05f 100644
--- a/src/output.c
+++ b/src/output.c
@@ -598,6 +598,16 @@ action_row (state_t *state)
}
}
+ /* Find the rules which are reduced. */
+ if (!glr_parser)
+ {
+ for (i = 0; i < ntokens; i++)
+ if (actrow[i] < 0 && actrow[i] != ACTION_MIN)
+ rules[item_number_as_rule_number (actrow[i])].useful = TRUE;
+ if (default_rule)
+ default_rule->useful = TRUE;
+ }
+
/* If have no default rule, the default is an error.
So replace any action which says "error" with "use default". */
@@ -671,6 +681,7 @@ static void
token_actions (void)
{
state_number_t i;
+ rule_number_t r;
int nconflict = conflicts_total_count ();
rule_number_t *yydefact = XCALLOC (rule_number_t, nstates);
@@ -678,6 +689,13 @@ token_actions (void)
actrow = XCALLOC (action_t, ntokens);
conflrow = XCALLOC (unsigned int, ntokens);
+ /* Now that the parser was computed, we can find which rules are
+ really reduced, and which are not because of SR or RR conflicts.
+ */
+ if (!glr_parser)
+ for (r = 0; r < nrules; ++r)
+ rules[r].useful = FALSE;
+
if (glr_parser)
{
conflict_list = XCALLOC (unsigned int, 1 + 2 * nconflict);
@@ -696,6 +714,17 @@ token_actions (void)
muscle_insert_rule_number_table ("defact", yydefact,
yydefact[0], 1, nstates);
+
+ if (!glr_parser)
+ for (r = 0; r < nrules ; ++r)
+ if (!rules[r].useful)
+ {
+ LOCATION_PRINT (stderr, rules[r].location);
+ fprintf (stderr, ": %s: %s: ",
+ _("warning"), _("rule never reduced because of conflicts"));
+ rule_print (&rules[r], stderr);
+ }
+
XFREE (actrow);
XFREE (conflrow);
XFREE (yydefact);
diff --git a/src/print.c b/src/print.c
index 1227765b..2a07affa 100644
--- a/src/print.c
+++ b/src/print.c
@@ -286,8 +286,11 @@ print_reduction (FILE *out, size_t width,
fputc (' ', out);
if (!enabled)
fputc ('[', out);
- fprintf (out, _("reduce using rule %d (%s)"),
- rule->number, rule->lhs->tag);
+ if (rule->number)
+ fprintf (out, _("reduce using rule %d (%s)"),
+ rule->number, rule->lhs->tag);
+ else
+ fprintf (out, _("accept"));
if (!enabled)
fputc (']', out);
fputc ('\n', out);
@@ -393,19 +396,6 @@ print_reductions (FILE *out, state_t *state)
static void
print_actions (FILE *out, state_t *state)
{
- reductions_t *redp = state->reductions;
- transitions_t *transitions = state->transitions;
-
- if (transitions->num == 0 && redp->num == 0)
- {
- fputc ('\n', out);
- if (state->number == final_state->number)
- fprintf (out, _(" $default\taccept\n"));
- else
- fprintf (out, _(" NO ACTIONS\n"));
- return;
- }
-
/* Print shifts. */
print_transitions (state, out, TRUE);
print_errs (out, state);
diff --git a/tests/conflicts.at b/tests/conflicts.at
index 84b4fcda..d0da937b 100644
--- a/tests/conflicts.at
+++ b/tests/conflicts.at
@@ -37,7 +37,9 @@ exp: e 'e';
e: 'e' | /* Nothing. */;
]])
-AT_CHECK([bison input.y -o input.c])
+AT_CHECK([bison input.y -o input.c], 0, [],
+[[input.y:4.8: warning: rule never reduced because of conflicts: e: /* empty */
+]])
AT_CLEANUP
@@ -203,7 +205,7 @@ state 3
0 $accept: exp $end .
- $default accept
+ $default accept
state 4
@@ -306,7 +308,7 @@ state 3
0 $accept: exp $end .
- $default accept
+ $default accept
state 4
@@ -369,8 +371,9 @@ id : '0';
]])
AT_CHECK([bison input.y -o input.c --report=all], 0, [],
-[input.y contains 1 reduce/reduce conflict.
-])
+[[input.y contains 1 reduce/reduce conflict.
+input.y:4.4-8: warning: rule never reduced because of conflicts: id: '0'
+]])
# Check the contents of the report.
AT_CHECK([cat input.output], [],
@@ -458,7 +461,7 @@ state 5
0 $accept: exp $end .
- $default accept
+ $default accept
]])
AT_CLEANUP
diff --git a/tests/regression.at b/tests/regression.at
index ca5c2f97..f8768f76 100644
--- a/tests/regression.at
+++ b/tests/regression.at
@@ -228,7 +228,7 @@ state 5
0 $accept: expr $end .
- $default accept
+ $default accept
state 6
@@ -456,7 +456,7 @@ state 5
0 $accept: CONST_DEC_PART $end .
- $default accept
+ $default accept
state 6
@@ -601,7 +601,7 @@ static const unsigned char yyr2[] =
};
static const unsigned char yydefact[] =
{
- 3, 0, 0, 2, 0, 0, 0, 3, 4, 3,
+ 3, 0, 0, 2, 0, 0, 1, 3, 4, 3,
6, 5
};
static const signed char yydefgoto[] =