From 868d2d96387042d8aba99fe427e76d186a7a4759 Mon Sep 17 00:00:00 2001
From: "Joel E. Denny" <jdenny@ces.clemson.edu>
Date: Sat, 29 Jul 2006 04:11:33 +0000
Subject: [PATCH] Clean up handling of %destructor for the end token (token 0).
Discussed starting at
<http://lists.gnu.org/archive/html/bison-patches/2006-07/msg00019.html> and
<http://lists.gnu.org/archive/html/help-bison/2006-07/msg00013.html>.
Make the skeletons consistent in how they pop the end token and invoke
its %destructor.
* data/glr.c (yyrecoverSyntaxError, yyparse): Don't pop the start
state, which has token number 0, since this would invoke the
%destructor for the end token.
* data/lalr1.cc (yy::parser::parse): Don't check for the final state
until after shifting the end token, or else it won't be popped.
* data/yacc.c (yyparse): Likewise.
* data/glr.c (yyparse): Clear the lookahead after shifting it even when
it's the end token. Upon termination, destroy an unshifted lookahead
even when it's the end token.
* data/lalr1.cc (yy::parser::parse): Likewise.
* data/yacc.c (yyparse): Likewise.
* src/reader.c (packgram): Don't check rule 0. This suppresses unused
value warnings for the end token when the user gives the end token a
%destructor.
* tests/actions.at (Printers and Destructors): Test all the above.
---
ChangeLog | 29 ++++++++++++++++++++++++++
data/glr.c | 11 +++++-----
data/lalr1.cc | 19 ++++++++---------
data/yacc.c | 16 ++++++---------
src/reader.c | 6 +++++-
tests/actions.at | 53 ++++++++++++++++++++++++++++++++++++++++++------
6 files changed, 101 insertions(+), 33 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 6880017d..d603301c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,32 @@
+2006-07-29 Joel E. Denny <jdenny@ces.clemson.edu>
+
+ Clean up handling of %destructor for the end token (token 0).
+ Discussed starting at
+ <http://lists.gnu.org/archive/html/bison-patches/2006-07/msg00019.html>
+ and
+ <http://lists.gnu.org/archive/html/help-bison/2006-07/msg00013.html>.
+
+ Make the skeletons consistent in how they pop the end token and invoke
+ its %destructor.
+ * data/glr.c (yyrecoverSyntaxError, yyparse): Don't pop the start
+ state, which has token number 0, since this would invoke the
+ %destructor for the end token.
+ * data/lalr1.cc (yy::parser::parse): Don't check for the final state
+ until after shifting the end token, or else it won't be popped.
+ * data/yacc.c (yyparse): Likewise.
+
+ * data/glr.c (yyparse): Clear the lookahead after shifting it even when
+ it's the end token. Upon termination, destroy an unshifted lookahead
+ even when it's the end token.
+ * data/lalr1.cc (yy::parser::parse): Likewise.
+ * data/yacc.c (yyparse): Likewise.
+
+ * src/reader.c (packgram): Don't check rule 0. This suppresses unused
+ value warnings for the end token when the user gives the end token a
+ %destructor.
+
+ * tests/actions.at (Printers and Destructors): Test all the above.
+
2006-07-24 Paul Eggert <eggert@cs.ucla.edu>
Update to latest gnulib and gettext versions.
diff --git a/data/glr.c b/data/glr.c
index 836df503..7c3d998d 100644
--- a/data/glr.c
+++ b/data/glr.c
@@ -2261,7 +2261,8 @@ yyrecoverSyntaxError (yyGLRStack* yystackp]b4_user_formals[)
}
}
]b4_locations_if([[ yystackp->yyerror_range[1].yystate.yyloc = yys->yyloc;]])[
- yydestroyGLRState ("Error: popping", yys]b4_user_args[);
+ if (yys->yypred != NULL)
+ yydestroyGLRState ("Error: popping", yys]b4_user_args[);
yystackp->yytops.yystates[0] = yys->yypred;
yystackp->yynextFree -= 1;
yystackp->yyspaceLeft += 1;
@@ -2373,8 +2374,7 @@ m4_popdef([b4_at_dollar])])dnl
if (yyisShiftAction (yyaction))
{
YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
- if (yychar != YYEOF)
- yychar = YYEMPTY;
+ yychar = YYEMPTY;
yyposn += 1;
yyglrShift (&yystack, 0, yyaction, yyposn, &yylval, &yylloc);
if (0 < yystack.yyerrState)
@@ -2490,7 +2490,7 @@ m4_popdef([b4_at_dollar])])dnl
goto yyreturn;
yyreturn:
- if (yychar != YYEOF && yychar != YYEMPTY)
+ if (yychar != YYEMPTY)
yydestruct ("Cleanup: discarding lookahead",
YYTRANSLATE (yychar),
&yylval]b4_locations_if([, &yylloc])[]b4_user_args[);
@@ -2512,7 +2512,8 @@ m4_popdef([b4_at_dollar])])dnl
{
yyGLRState *yys = yystates[yyk];
]b4_locations_if([[ yystack.yyerror_range[1].yystate.yyloc = yys->yyloc;]]
-)[ yydestroyGLRState ("Cleanup: popping", yys]b4_user_args[);
+)[ if (yys->yypred != NULL)
+ yydestroyGLRState ("Cleanup: popping", yys]b4_user_args[);
yystates[yyk] = yys->yypred;
yystack.yynextFree -= 1;
yystack.yyspaceLeft += 1;
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 25b9160c..377659e5 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -567,6 +567,11 @@ m4_popdef([b4_at_dollar])])dnl
yynewstate:
yystate_stack_.push (yystate);
YYCDEBUG << "Entering state " << yystate << std::endl;
+
+ /* Accept? */
+ if (yystate == yyfinal_)
+ goto yyacceptlab;
+
goto yybackup;
/* Backup. */
@@ -616,16 +621,11 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
goto yyreduce;
}
- /* Accept? */
- if (yyn == yyfinal_)
- goto yyacceptlab;
-
/* Shift the lookahead token. */
YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
- /* Discard the token being shifted unless it is eof. */
- if (yychar != yyeof_)
- yychar = yyempty_;
+ /* Discard the token being shifted. */
+ yychar = yyempty_;
yysemantic_stack_.push (yylval);
yylocation_stack_.push (yylloc);
@@ -780,9 +780,6 @@ b4_error_verbose_if([, yytoken])[));
YY_STACK_PRINT ();
}
- if (yyn == yyfinal_)
- goto yyacceptlab;
-
yyerror_range[1] = yylloc;
// Using YYLLOC is tempting, but would change the location of
// the lookahead. YYLOC is available though.
@@ -808,7 +805,7 @@ b4_error_verbose_if([, yytoken])[));
goto yyreturn;
yyreturn:
- if (yychar != yyeof_ && yychar != yyempty_)
+ if (yychar != yyempty_)
yydestruct_ ("Cleanup: discarding lookahead", yytoken, &yylval, &yylloc);
/* Do not reclaim the symbols of the rule which action triggered
diff --git a/data/yacc.c b/data/yacc.c
index cdc69203..74a014f1 100644
--- a/data/yacc.c
+++ b/data/yacc.c
@@ -1164,6 +1164,9 @@ m4_ifdef([b4_at_dollar_used], [[ yylsp[0] = yylloc;
YYDPRINTF ((stderr, "Entering state %d\n", yystate));
+ if (yystate == YYFINAL)
+ YYACCEPT;
+
goto yybackup;
/*-----------.
@@ -1213,9 +1216,6 @@ yybackup:
goto yyreduce;
}
- if (yyn == YYFINAL)
- YYACCEPT;
-
/* Count tokens shifted since error; after three, turn off error
status. */
if (yyerrstatus)
@@ -1224,9 +1224,8 @@ yybackup:
/* Shift the lookahead token. */
YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
- /* Discard the shifted token unless it is eof. */
- if (yychar != YYEOF)
- yychar = YYEMPTY;
+ /* Discard the shifted token. */
+ yychar = YYEMPTY;
yystate = yyn;
*++yyvsp = yylval;
@@ -1418,9 +1417,6 @@ yyerrlab1:
YY_STACK_PRINT (yyss, yyssp);
}
- if (yyn == YYFINAL)
- YYACCEPT;
-
*++yyvsp = yylval;
]b4_locations_if([[
yyerror_range[1] = yylloc;
@@ -1461,7 +1457,7 @@ yyexhaustedlab:
#endif
yyreturn:
- if (yychar != YYEOF && yychar != YYEMPTY)
+ if (yychar != YYEMPTY)
yydestruct ("Cleanup: discarding lookahead",
yytoken, &yylval]b4_locations_if([, &yylloc])[]b4_user_args[);
/* Do not reclaim the symbols of the rule which action triggered
diff --git a/src/reader.c b/src/reader.c
index 800ecc22..928be1b8 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -488,7 +488,11 @@ packgram (void)
rule. Thus, the midrule actions have already been scanned in order to
set `used' flags for this rule's rhs, so grammar_rule_check will work
properly. */
- grammar_rule_check (p);
+ /* Don't check the generated rule 0. It has no action, so some rhs
+ symbols may appear unused, but the parsing algorithm ensures that
+ %destructor's are invoked appropriately. */
+ if (p != grammar)
+ grammar_rule_check (p);
for (p = p->next; p && p->sym; p = p->next)
{
diff --git a/tests/actions.at b/tests/actions.at
index 6267b74e..2a2bce75 100644
--- a/tests/actions.at
+++ b/tests/actions.at
@@ -197,8 +197,9 @@ AT_LALR1_CC_IF([typedef yy::location YYLTYPE;
]AT_LALR1_CC_IF([], [static void yyerror (const char *msg);])
[}
-]m4_ifval([$6], [%type <ival> '(' 'x' 'y' ')' ';' thing line input])[
+]m4_ifval([$6], [%type <ival> '(' 'x' 'y' ')' ';' thing line input END])[
+/* FIXME: This %printer isn't actually tested. */
%printer
{
]AT_LALR1_CC_IF([debug_stream () << $$;],
@@ -226,6 +227,11 @@ AT_LALR1_CC_IF([typedef yy::location YYLTYPE;
{ printf ("Freeing token 'y' (%d@%d-%d)\n", $$, RANGE (@$)); }
'y'
+%token END 0
+%destructor
+ { printf ("Freeing token END (%d@%d-%d)\n", $$, RANGE (@$)); }
+ END
+
%%
/*
This grammar is made to exercise error recovery.
@@ -241,7 +247,7 @@ input:
printf ("input (%d@%d-%d): /* Nothing */\n", $$, RANGE (@$));
}
| line input /* Right recursive to load the stack so that popping at
- EOF can be exercised. */
+ END can be exercised. */
{
$$ = 2;
printf ("input (%d@%d-%d): line (%d@%d-%d) input (%d@%d-%d)\n",
@@ -308,7 +314,7 @@ yylex (]AT_LEX_FORMALS[)
if (source[c])
printf ("sending: '%c'", source[c]);
else
- printf ("sending: EOF");
+ printf ("sending: END");
printf (" (%d@%d-%d)\n", c, RANGE (]AT_LOC[));
return source[c];
}
@@ -372,9 +378,10 @@ sending: 'x' (1@10-19)
thing (1@10-19): 'x' (1@10-19)
sending: ')' (2@20-29)
line (0@0-29): '(' (0@0-9) thing (1@10-19) ')' (2@20-29)
-sending: EOF (3@30-39)
+sending: END (3@30-39)
input (0@29-29): /* Nothing */
input (2@0-29): line (0@0-29) input (0@29-29)
+Freeing token END (3@30-39)
Freeing nterm input (2@0-29)
Successful parse.
]])
@@ -391,9 +398,10 @@ sending: 'y' (1@10-19)
Freeing token 'y' (1@10-19)
sending: ')' (2@20-29)
line (-1@0-29): '(' (0@0-9) error (@10-19) ')' (2@20-29)
-sending: EOF (3@30-39)
+sending: END (3@30-39)
input (0@29-29): /* Nothing */
input (2@0-29): line (-1@0-29) input (0@29-29)
+Freeing token END (3@30-39)
Freeing nterm input (2@0-29)
Successful parse.
]])
@@ -445,12 +453,45 @@ input (0@129-129): /* Nothing */
input (2@100-129): line (10@100-129) input (0@129-129)
input (2@70-129): line (7@70-99) input (2@100-129)
input (2@0-129): line (-1@0-69) input (2@70-129)
-130-139: syntax error, unexpected 'y', expecting $end
+130-139: syntax error, unexpected 'y', expecting END
Freeing nterm input (2@0-129)
Freeing token 'y' (13@130-139)
Parsing FAILED.
]])
+
+# Syntax error caught by the parser where lookahead = END
+# --------------------------------------------------------
+# Load the stack and provoke an error that cannot be caught by the
+# grammar, to check that the stack is cleared. And make sure the
+# lookahead is freed.
+#
+# '(', 'x', ')',
+# '(', 'x', ')',
+# 'x'
+AT_PARSER_CHECK([./input '(x)(x)x'], 1,
+[[sending: '(' (0@0-9)
+sending: 'x' (1@10-19)
+thing (1@10-19): 'x' (1@10-19)
+sending: ')' (2@20-29)
+line (0@0-29): '(' (0@0-9) thing (1@10-19) ')' (2@20-29)
+sending: '(' (3@30-39)
+sending: 'x' (4@40-49)
+thing (4@40-49): 'x' (4@40-49)
+sending: ')' (5@50-59)
+line (3@30-59): '(' (3@30-39) thing (4@40-49) ')' (5@50-59)
+sending: 'x' (6@60-69)
+thing (6@60-69): 'x' (6@60-69)
+sending: END (7@70-79)
+70-79: syntax error, unexpected END, expecting 'x'
+Freeing nterm thing (6@60-69)
+Freeing nterm line (3@30-59)
+Freeing nterm line (0@0-29)
+Freeing token END (7@70-79)
+Parsing FAILED.
+]])
+
+
# Check destruction upon stack overflow
# -------------------------------------
# Upon stack overflow, all symbols on the stack should be destroyed.
--
2.47.2