637 lines
18 KiB
C
637 lines
18 KiB
C
/* Find and resolve or report lookahead conflicts for bison,
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Copyright (C) 1984, 1989, 1992, 2000-2007, 2009-2012 Free Software
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Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include <config.h>
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#include "system.h"
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#include <bitset.h>
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#include "LR0.h"
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#include "complain.h"
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#include "conflicts.h"
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#include "files.h"
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#include "getargs.h"
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#include "gram.h"
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#include "lalr.h"
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#include "print-xml.h"
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#include "reader.h"
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#include "state.h"
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#include "symtab.h"
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/* -1 stands for not specified. */
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int expected_sr_conflicts = -1;
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int expected_rr_conflicts = -1;
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static char *conflicts;
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static struct obstack solved_conflicts_obstack;
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static struct obstack solved_conflicts_xml_obstack;
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static bitset shift_set;
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static bitset lookahead_set;
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enum conflict_resolution
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{
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shift_resolution,
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reduce_resolution,
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left_resolution,
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right_resolution,
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nonassoc_resolution
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};
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/*----------------------------------------------------------------.
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| Explain how an SR conflict between TOKEN and RULE was resolved: |
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| RESOLUTION. |
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`----------------------------------------------------------------*/
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static inline void
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log_resolution (rule *r, symbol_number token,
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enum conflict_resolution resolution)
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{
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if (report_flag & report_solved_conflicts)
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{
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/* The description of the resolution. */
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switch (resolution)
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{
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case shift_resolution:
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case right_resolution:
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obstack_printf (&solved_conflicts_obstack,
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_(" Conflict between rule %d and token %s"
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" resolved as shift"),
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r->number,
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symbols[token]->tag);
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break;
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case reduce_resolution:
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case left_resolution:
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obstack_printf (&solved_conflicts_obstack,
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_(" Conflict between rule %d and token %s"
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" resolved as reduce"),
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r->number,
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symbols[token]->tag);
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break;
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case nonassoc_resolution:
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obstack_printf (&solved_conflicts_obstack,
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_(" Conflict between rule %d and token %s"
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" resolved as an error"),
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r->number,
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symbols[token]->tag);
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break;
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}
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/* The reason. */
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switch (resolution)
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{
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case shift_resolution:
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obstack_printf (&solved_conflicts_obstack,
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" (%s < %s)",
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r->prec->tag,
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symbols[token]->tag);
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break;
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case reduce_resolution:
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obstack_printf (&solved_conflicts_obstack,
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" (%s < %s)",
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symbols[token]->tag,
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r->prec->tag);
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break;
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case left_resolution:
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obstack_printf (&solved_conflicts_obstack,
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" (%%left %s)",
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symbols[token]->tag);
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break;
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case right_resolution:
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obstack_printf (&solved_conflicts_obstack,
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" (%%right %s)",
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symbols[token]->tag);
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break;
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case nonassoc_resolution:
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obstack_printf (&solved_conflicts_obstack,
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" (%%nonassoc %s)",
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symbols[token]->tag);
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break;
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}
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obstack_sgrow (&solved_conflicts_obstack, ".\n");
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}
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/* XML report */
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if (xml_flag)
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{
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/* The description of the resolution. */
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switch (resolution)
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{
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case shift_resolution:
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case right_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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" <resolution rule=\"%d\" symbol=\"%s\""
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" type=\"shift\">",
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r->number,
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xml_escape (symbols[token]->tag));
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break;
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case reduce_resolution:
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case left_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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" <resolution rule=\"%d\" symbol=\"%s\""
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" type=\"reduce\">",
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r->number,
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xml_escape (symbols[token]->tag));
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break;
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case nonassoc_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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" <resolution rule=\"%d\" symbol=\"%s\""
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" type=\"error\">",
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r->number,
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xml_escape (symbols[token]->tag));
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break;
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}
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/* The reason. */
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switch (resolution)
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{
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case shift_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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"%s < %s",
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xml_escape_n (0, r->prec->tag),
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xml_escape_n (1, symbols[token]->tag));
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break;
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case reduce_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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"%s < %s",
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xml_escape_n (0, symbols[token]->tag),
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xml_escape_n (1, r->prec->tag));
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break;
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case left_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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"%%left %s",
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xml_escape (symbols[token]->tag));
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break;
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case right_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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"%%right %s",
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xml_escape (symbols[token]->tag));
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break;
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case nonassoc_resolution:
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obstack_printf (&solved_conflicts_xml_obstack,
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"%%nonassoc %s",
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xml_escape (symbols[token]->tag));
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break;
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}
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obstack_sgrow (&solved_conflicts_xml_obstack, "</resolution>\n");
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}
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}
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/*------------------------------------------------------------------.
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| Turn off the shift recorded for the specified token in the |
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| specified state. Used when we resolve a shift-reduce conflict in |
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| favor of the reduction or as an error (%nonassoc). |
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`------------------------------------------------------------------*/
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static void
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flush_shift (state *s, int token)
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{
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transitions *trans = s->transitions;
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int i;
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bitset_reset (lookahead_set, token);
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for (i = 0; i < trans->num; i++)
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if (!TRANSITION_IS_DISABLED (trans, i)
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&& TRANSITION_SYMBOL (trans, i) == token)
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TRANSITION_DISABLE (trans, i);
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}
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/*--------------------------------------------------------------------.
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| Turn off the reduce recorded for the specified token in the |
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| specified lookahead set. Used when we resolve a shift-reduce |
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| conflict in favor of the shift or as an error (%nonassoc). |
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`--------------------------------------------------------------------*/
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static void
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flush_reduce (bitset lookahead_tokens, int token)
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{
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bitset_reset (lookahead_tokens, token);
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}
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/*------------------------------------------------------------------.
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| Attempt to resolve shift-reduce conflict for one rule by means of |
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| precedence declarations. It has already been checked that the |
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| rule has a precedence. A conflict is resolved by modifying the |
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| shift or reduce tables so that there is no longer a conflict. |
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| |
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| RULENO is the number of the lookahead bitset to consider. |
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| |
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| ERRORS and NERRS can be used to store discovered explicit |
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| errors. |
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`------------------------------------------------------------------*/
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static void
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resolve_sr_conflict (state *s, int ruleno, symbol **errors, int *nerrs)
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{
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symbol_number i;
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reductions *reds = s->reductions;
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/* Find the rule to reduce by to get precedence of reduction. */
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rule *redrule = reds->rules[ruleno];
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int redprec = redrule->prec->prec;
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bitset lookahead_tokens = reds->lookahead_tokens[ruleno];
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for (i = 0; i < ntokens; i++)
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if (bitset_test (lookahead_tokens, i)
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&& bitset_test (lookahead_set, i)
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&& symbols[i]->prec)
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{
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/* Shift-reduce conflict occurs for token number i
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and it has a precedence.
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The precedence of shifting is that of token i. */
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if (symbols[i]->prec < redprec)
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{
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log_resolution (redrule, i, reduce_resolution);
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flush_shift (s, i);
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}
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else if (symbols[i]->prec > redprec)
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{
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log_resolution (redrule, i, shift_resolution);
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flush_reduce (lookahead_tokens, i);
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}
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else
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/* Matching precedence levels.
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For left association, keep only the reduction.
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For right association, keep only the shift.
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For nonassociation, keep neither. */
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switch (symbols[i]->assoc)
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{
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default:
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abort ();
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case right_assoc:
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log_resolution (redrule, i, right_resolution);
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flush_reduce (lookahead_tokens, i);
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break;
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case left_assoc:
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log_resolution (redrule, i, left_resolution);
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flush_shift (s, i);
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break;
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case non_assoc:
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log_resolution (redrule, i, nonassoc_resolution);
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flush_shift (s, i);
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flush_reduce (lookahead_tokens, i);
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/* Record an explicit error for this token. */
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errors[(*nerrs)++] = symbols[i];
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break;
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}
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}
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}
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/*-------------------------------------------------------------------.
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| Solve the S/R conflicts of state S using the |
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| precedence/associativity, and flag it inconsistent if it still has |
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| conflicts. ERRORS can be used as storage to compute the list of |
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| lookahead tokens on which S raises a syntax error (%nonassoc). |
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`-------------------------------------------------------------------*/
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static void
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set_conflicts (state *s, symbol **errors)
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{
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int i;
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transitions *trans = s->transitions;
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reductions *reds = s->reductions;
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int nerrs = 0;
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if (s->consistent)
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return;
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bitset_zero (lookahead_set);
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FOR_EACH_SHIFT (trans, i)
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bitset_set (lookahead_set, TRANSITION_SYMBOL (trans, i));
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/* Loop over all rules which require lookahead in this state. First
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check for shift-reduce conflict, and try to resolve using
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precedence. */
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for (i = 0; i < reds->num; ++i)
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if (reds->rules[i]->prec && reds->rules[i]->prec->prec
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&& !bitset_disjoint_p (reds->lookahead_tokens[i], lookahead_set))
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resolve_sr_conflict (s, i, errors, &nerrs);
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if (nerrs)
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{
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/* Some tokens have been explicitly made errors. Allocate a
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permanent errs structure for this state, to record them. */
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state_errs_set (s, nerrs, errors);
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}
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if (obstack_object_size (&solved_conflicts_obstack))
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{
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obstack_1grow (&solved_conflicts_obstack, '\0');
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s->solved_conflicts = obstack_finish (&solved_conflicts_obstack);
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}
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if (obstack_object_size (&solved_conflicts_xml_obstack))
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{
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obstack_1grow (&solved_conflicts_xml_obstack, '\0');
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s->solved_conflicts_xml = obstack_finish (&solved_conflicts_xml_obstack);
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}
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/* Loop over all rules which require lookahead in this state. Check
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for conflicts not resolved above. */
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for (i = 0; i < reds->num; ++i)
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{
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if (!bitset_disjoint_p (reds->lookahead_tokens[i], lookahead_set))
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conflicts[s->number] = 1;
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bitset_or (lookahead_set, lookahead_set, reds->lookahead_tokens[i]);
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}
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}
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/*----------------------------------------------------------------.
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| Solve all the S/R conflicts using the precedence/associativity, |
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| and flag as inconsistent the states that still have conflicts. |
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`----------------------------------------------------------------*/
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void
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conflicts_solve (void)
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{
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state_number i;
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/* List of lookahead tokens on which we explicitly raise a syntax error. */
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symbol **errors = xnmalloc (ntokens + 1, sizeof *errors);
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conflicts = xcalloc (nstates, sizeof *conflicts);
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shift_set = bitset_create (ntokens, BITSET_FIXED);
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lookahead_set = bitset_create (ntokens, BITSET_FIXED);
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obstack_init (&solved_conflicts_obstack);
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obstack_init (&solved_conflicts_xml_obstack);
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for (i = 0; i < nstates; i++)
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{
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set_conflicts (states[i], errors);
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/* For uniformity of the code, make sure all the states have a valid
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`errs' member. */
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if (!states[i]->errs)
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states[i]->errs = errs_new (0, 0);
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}
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free (errors);
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}
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void
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conflicts_update_state_numbers (state_number old_to_new[],
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state_number nstates_old)
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{
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state_number i;
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for (i = 0; i < nstates_old; ++i)
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if (old_to_new[i] != nstates_old)
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conflicts[old_to_new[i]] = conflicts[i];
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}
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/*---------------------------------------------.
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| Count the number of shift/reduce conflicts. |
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`---------------------------------------------*/
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static int
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count_sr_conflicts (state *s)
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{
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int i;
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int src_count = 0;
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transitions *trans = s->transitions;
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reductions *reds = s->reductions;
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if (!trans)
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return 0;
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bitset_zero (lookahead_set);
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bitset_zero (shift_set);
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FOR_EACH_SHIFT (trans, i)
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bitset_set (shift_set, TRANSITION_SYMBOL (trans, i));
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for (i = 0; i < reds->num; ++i)
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bitset_or (lookahead_set, lookahead_set, reds->lookahead_tokens[i]);
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bitset_and (lookahead_set, lookahead_set, shift_set);
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src_count = bitset_count (lookahead_set);
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return src_count;
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}
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/*----------------------------------------------------------------.
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| Count the number of reduce/reduce conflicts. If ONE_PER_TOKEN, |
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| count one conflict for each token that has any reduce/reduce |
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| conflicts. Otherwise, count one conflict for each pair of |
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| conflicting reductions. |
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+`----------------------------------------------------------------*/
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static int
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count_rr_conflicts (state *s, bool one_per_token)
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{
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int i;
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reductions *reds = s->reductions;
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int rrc_count = 0;
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for (i = 0; i < ntokens; i++)
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{
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int count = 0;
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int j;
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for (j = 0; j < reds->num; ++j)
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if (bitset_test (reds->lookahead_tokens[j], i))
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count++;
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if (count >= 2)
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rrc_count += one_per_token ? 1 : count-1;
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}
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return rrc_count;
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}
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/*--------------------------------------------------------.
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| Report the number of conflicts, using the Yacc format. |
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`--------------------------------------------------------*/
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static void
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conflict_report (FILE *out, int src_num, int rrc_num)
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{
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if (src_num && rrc_num)
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fprintf (out, _("conflicts: %d shift/reduce, %d reduce/reduce\n"),
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src_num, rrc_num);
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else if (src_num)
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fprintf (out, _("conflicts: %d shift/reduce\n"), src_num);
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else if (rrc_num)
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fprintf (out, _("conflicts: %d reduce/reduce\n"), rrc_num);
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}
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/*-----------------------------------------------------------.
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| Output the detailed description of states with conflicts. |
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`-----------------------------------------------------------*/
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void
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conflicts_output (FILE *out)
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{
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bool printed_sth = false;
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state_number i;
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for (i = 0; i < nstates; i++)
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{
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state *s = states[i];
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if (conflicts[i])
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{
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fprintf (out, _("State %d "), i);
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conflict_report (out, count_sr_conflicts (s),
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count_rr_conflicts (s, true));
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printed_sth = true;
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}
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}
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if (printed_sth)
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fputs ("\n\n", out);
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}
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/*--------------------------------------------------------.
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| Total the number of S/R and R/R conflicts. Unlike the |
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| code in conflicts_output, however, count EACH pair of |
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| reductions for the same state and lookahead as one |
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| conflict. |
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`--------------------------------------------------------*/
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int
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conflicts_total_count (void)
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{
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state_number i;
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int count;
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/* Conflicts by state. */
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count = 0;
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for (i = 0; i < nstates; i++)
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if (conflicts[i])
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{
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count += count_sr_conflicts (states[i]);
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count += count_rr_conflicts (states[i], false);
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}
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return count;
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}
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/*------------------------------------------.
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| Reporting the total number of conflicts. |
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`------------------------------------------*/
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void
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conflicts_print (void)
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{
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/* Is the number of SR conflicts OK? Either EXPECTED_CONFLICTS is
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not set, and then we want 0 SR, or else it is specified, in which
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case we want equality. */
|
||
bool src_ok;
|
||
bool rrc_ok;
|
||
|
||
int src_total = 0;
|
||
int rrc_total = 0;
|
||
int src_expected;
|
||
int rrc_expected;
|
||
|
||
/* Conflicts by state. */
|
||
{
|
||
state_number i;
|
||
|
||
for (i = 0; i < nstates; i++)
|
||
if (conflicts[i])
|
||
{
|
||
src_total += count_sr_conflicts (states[i]);
|
||
rrc_total += count_rr_conflicts (states[i], true);
|
||
}
|
||
}
|
||
|
||
if (! glr_parser && rrc_total > 0 && expected_rr_conflicts != -1)
|
||
{
|
||
warn (_("%%expect-rr applies only to GLR parsers"));
|
||
expected_rr_conflicts = -1;
|
||
}
|
||
|
||
src_expected = expected_sr_conflicts == -1 ? 0 : expected_sr_conflicts;
|
||
rrc_expected = expected_rr_conflicts == -1 ? 0 : expected_rr_conflicts;
|
||
src_ok = src_total == src_expected;
|
||
rrc_ok = rrc_total == rrc_expected;
|
||
|
||
/* If there are as many RR conflicts and SR conflicts as
|
||
expected, then there is nothing to report. */
|
||
if (rrc_ok & src_ok)
|
||
return;
|
||
|
||
/* Report the total number of conflicts on STDERR. */
|
||
if (expected_sr_conflicts == -1 && expected_rr_conflicts == -1)
|
||
{
|
||
if (!(warnings_flag & warnings_conflicts_sr))
|
||
src_total = 0;
|
||
if (!(warnings_flag & warnings_conflicts_rr))
|
||
rrc_total = 0;
|
||
}
|
||
if (src_total | rrc_total)
|
||
{
|
||
if (expected_sr_conflicts == -1 && expected_rr_conflicts == -1)
|
||
set_warning_issued ();
|
||
if (! yacc_flag)
|
||
fprintf (stderr, "%s: ", current_file);
|
||
conflict_report (stderr, src_total, rrc_total);
|
||
}
|
||
|
||
if (expected_sr_conflicts != -1 || expected_rr_conflicts != -1)
|
||
{
|
||
if (! src_ok)
|
||
complain (ngettext ("expected %d shift/reduce conflict",
|
||
"expected %d shift/reduce conflicts",
|
||
src_expected),
|
||
src_expected);
|
||
if (! rrc_ok)
|
||
complain (ngettext ("expected %d reduce/reduce conflict",
|
||
"expected %d reduce/reduce conflicts",
|
||
rrc_expected),
|
||
rrc_expected);
|
||
}
|
||
}
|
||
|
||
|
||
void
|
||
conflicts_free (void)
|
||
{
|
||
free (conflicts);
|
||
bitset_free (shift_set);
|
||
bitset_free (lookahead_set);
|
||
obstack_free (&solved_conflicts_obstack, NULL);
|
||
obstack_free (&solved_conflicts_xml_obstack, NULL);
|
||
}
|