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yysyntax_error: fix for consistent error with lookahead.

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* NEWS (2.5): Document.
* data/yacc.c (yysyntax_error): In a verbose syntax error
message while in a consistent state with a default action (which
must be an error action given that yysyntax_error is being
invoked), continue to drop the expected token list, but don't
drop the unexpected token unless there actually is no lookahead.
Moreover, handle that internally instead of returning 1 to tell
the caller to do it.  With that meaning of 1 gone, renumber
return codes more usefully.
(yyparse, yypush_parse): Update yysyntax_error usage.  Most
importantly, set yytoken to YYEMPTY when there's no lookahead.
* data/glr.c (yyreportSyntaxError): As in yacc.c, don't drop the
unexpected token unless there actually is no lookahead.
* data/lalr1.cc (yy::parser::parse): If there's no lookahead,
set yytoken to yyempty_ before invoking yysyntax_error_.
(yy::parser::yysyntax_error_): Again, don't drop the unexpected
token unless there actually is no lookahead.
* data/lalr1.java (YYParser::parse): If there's no lookahead,
set yytoken to yyempty_ before invoking yysyntax_error.
(YYParser::yysyntax_error): Again, don't drop the unexpected
token unless there actually is no lookahead.
* tests/conflicts.at (%error-verbose and consistent
errors): Extend test group to further reveal how the previous
use of the simple "syntax error" message was too general.  Test
yacc.c, glr.c, lalr1.cc, and lalr1.java.  No longer an expected
failure.
* tests/java.at (AT_JAVA_COMPILE, AT_JAVA_PARSER_CHECK): Move
to...
* tests/local.at: ... here.
(_AT_BISON_OPTION_PUSHDEFS): Push AT_SKEL_JAVA_IF definition.
(AT_BISON_OPTION_POPDEFS): Pop it.
(AT_FULL_COMPILE): Extend to handle Java.
(cherry picked from commit d2060f0634)

Conflicts:

	data/lalr1.cc
	data/lalr1.java
	src/parse-gram.c
	src/parse-gram.h
	tests/java.at
This commit is contained in:
Joel E. Denny
2010-11-07 16:01:56 -05:00
parent 678094a2f5
commit 095a1d11ca
11 changed files with 603 additions and 265 deletions
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59
data/lalr1.cc
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@@ -719,6 +719,8 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
if (!yyerrstatus_)
{
++yynerrs_;
if (yychar == yyempty_)
yytoken = yyempty_;
error (yylloc, yysyntax_error_ (yystate, yytoken));
}
@@ -848,26 +850,52 @@ b4_error_verbose_if([int yystate, int yytoken],
[int, int])[)
{]b4_error_verbose_if([[
std::string yyres;
int yyn = yypact_[yystate];
if (yypact_ninf_ < yyn && yyn <= yylast_)
// Number of reported tokens (one for the "unexpected", one per
// "expected").
size_t yycount = 0;
// Its maximum.
enum { YYERROR_VERBOSE_ARGS_MAXIMUM = 5 };
// Arguments of yyformat.
char const *yyarg[YYERROR_VERBOSE_ARGS_MAXIMUM];
/* There are many possibilities here to consider:
- If this state is a consistent state with a default action, then
the only way this function was invoked is if the default action
is an error action. In that case, don't check for expected
tokens because there are none.
- The only way there can be no lookahead present (in yytoken) is
if this state is a consistent state with a default action.
Thus, detecting the absence of a lookahead is sufficient to
determine that there is no unexpected or expected token to
report. In that case, just report a simple "syntax error".
- Don't assume there isn't a lookahead just because this state is
a consistent state with a default action. There might have
been a previous inconsistent state, consistent state with a
non-default action, or user semantic action that manipulated
yychar.
- Of course, the expected token list depends on states to have
correct lookahead information, and it depends on the parser not
to perform extra reductions after fetching a lookahead from the
scanner and before detecting a syntax error. Thus, state
merging (from LALR or IELR) and default reductions corrupt the
expected token list. However, the list is correct for
canonical LR with one exception: it will still contain any
token that will not be accepted due to an error action in a
later state.
*/
if (yytoken != yyempty_)
{
yyarg[yycount++] = yytname_[yytoken];
int yyn = yypact_[yystate];
if (!yy_pact_value_is_default_ (yyn))
{
/* Start YYX at -YYN if negative to avoid negative indexes in
YYCHECK. In other words, skip the first -YYN actions for
this state because they are default actions. */
int yyxbegin = yyn < 0 ? -yyn : 0;
/* Stay within bounds of both yycheck and yytname. */
int yychecklim = yylast_ - yyn + 1;
int yyxend = yychecklim < yyntokens_ ? yychecklim : yyntokens_;
// Number of reported tokens (one for the "unexpected", one per
// "expected").
size_t yycount = 0;
// Its maximum.
enum { YYERROR_VERBOSE_ARGS_MAXIMUM = 5 };
// Arguments of yyformat.
char const *yyarg[YYERROR_VERBOSE_ARGS_MAXIMUM];
yyarg[yycount++] = yytname_[yytoken];
for (int yyx = yyxbegin; yyx < yyxend; ++yyx)
if (yycheck_[yyx + yyn] == yyx && yyx != yyterror_
&& !yy_table_value_is_error_ (yytable_[yyx + yyn]))
@@ -880,6 +908,8 @@ b4_error_verbose_if([int yystate, int yytoken],
else
yyarg[yycount++] = yytname_[yyx];
}
}
}
char const* yyformat = 0;
switch (yycount)
@@ -888,6 +918,7 @@ b4_error_verbose_if([int yystate, int yytoken],
case N: \
yyformat = S; \
break
YYCASE_(0, YY_("syntax error"));
YYCASE_(1, YY_("syntax error, unexpected %s"));
YYCASE_(2, YY_("syntax error, unexpected %s, expecting %s"));
YYCASE_(3, YY_("syntax error, unexpected %s, expecting %s or %s"));
@@ -895,6 +926,7 @@ b4_error_verbose_if([int yystate, int yytoken],
YYCASE_(5, YY_("syntax error, unexpected %s, expecting %s or %s or %s or %s"));
#undef YYCASE_
}
// Argument number.
size_t yyi = 0;
for (char const* yyp = yyformat; *yyp; ++yyp)
@@ -905,9 +937,6 @@ b4_error_verbose_if([int yystate, int yytoken],
}
else
yyres += *yyp;
}
else
yyres = YY_("syntax error");
return yyres;]], [[
return YY_("syntax error");]])[
}