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Clean up handling of %destructor for the end token (token 0).

Browse Source 
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.
This commit is contained in:
Joel E. Denny
2006-07-29 04:11:33 +00:00
parent 62a9592d3d
commit 868d2d9638
6 changed files with 101 additions and 33 deletions
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19
data/lalr1.cc
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@@ -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