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Avoid undefined behavior that accessed just before the start of an array.

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* src/reader.c (packgram): Prepend a new sentinel before ritem.
* src/lalr.c (build_relations): Rely on new sentinel.
* src/gram.c (gram_free): Adjust to new sentinel.
This commit is contained in:
Paul Eggert
2006-01-18 23:48:29 +00:00
parent 02d7cce6e2
commit e9ad4aeca5
4 changed files with 24 additions and 9 deletions
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8
ChangeLog
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@@ -1,3 +1,11 @@
2006-01-18 Paul Eggert <eggert@cs.ucla.edu>
Avoid undefined behavior that accessed just before the start of an
array. Problem reported by twlevo.
* src/reader.c (packgram): Prepend a new sentinel before ritem.
* src/lalr.c (build_relations): Rely on new sentinel.
* src/gram.c (gram_free): Adjust to new sentinel.
2006-01-12 Joel E. Denny <jdenny@ces.clemson.edu>
* data/glr.c (yyGLRStateSet): Rename yylookaheadStatuses to

5
src/gram.c
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@@ -1,6 +1,6 @@
/* Allocate input grammar variables for Bison.
Copyright (C) 1984, 1986, 1989, 2001, 2002, 2003, 2005 Free
Copyright (C) 1984, 1986, 1989, 2001, 2002, 2003, 2005, 2006 Free
Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
@@ -325,7 +325,8 @@ grammar_rules_never_reduced_report (const char *message)
void
grammar_free (void)
{
free (ritem);
if (ritem)
free (ritem - 1);
free (rules);
free (token_translations);
/* Free the symbol table data structure. */

14
src/lalr.c
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@@ -1,7 +1,7 @@
/* Compute look-ahead criteria for Bison.
Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005
Free Software Foundation, Inc.
Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005,
2006 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
@@ -247,11 +247,11 @@ build_relations (void)
{
bool done;
int length = 1;
item_number *rp;
item_number const *rp;
state *s = states[from_state[i]];
states1[0] = s->number;
for (rp = (*rulep)->rhs; *rp >= 0; rp++)
for (rp = (*rulep)->rhs; ! item_number_is_rule_number (*rp); rp++)
{
s = transitions_to (s->transitions,
item_number_as_symbol_number (*rp));
@@ -266,9 +266,11 @@ build_relations (void)
while (!done)
{
done = true;
/* Each rhs ends in an item number, and there is a
sentinel before the first rhs, so it is safe to
decrement RP here. */
rp--;
/* JF added rp>=ritem && I hope to god its right! */
if (rp >= ritem && ISVAR (*rp))
if (ISVAR (*rp))
{
/* Downcasting from item_number to symbol_number. */
edge[nedges++] = map_goto (states1[--length],

6
src/reader.c
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@@ -418,7 +418,11 @@ packgram (void)
rule_number ruleno = 0;
symbol_list *p = grammar;
ritem = xnmalloc (nritems, sizeof *ritem);
ritem = xnmalloc (nritems + 1, sizeof *ritem);
/* This sentinel is used by build_relations in gram.c. */
*ritem++ = 0;
rules = xnmalloc (nrules, sizeof *rules);
while (p)