b4_push_if([m4_define([b4_use_push_for_pull_flag], [[0]])],
[m4_define([b4_push_flag], [[1]])])])
+# Check the value of %define parse.lac, where LAC stands for lookahead
+# correction.
+b4_percent_define_default([[parse.lac]], [[none]])
+b4_percent_define_default([[parse.lac.es-capacity]], [[20]])
+b4_percent_define_check_values([[[[parse.lac]], [[full]], [[none]]]])
+b4_define_flag_if([lac])
+m4_define([b4_lac_flag],
+ [m4_if(b4_percent_define_get([[parse.lac]]),
+ [none], [[0]], [[1]])])
+
m4_include(b4_pkgdatadir/[c.m4])
## ---------------- ##
{ \
yychar = (Token); \
yylval = (Value); \
- YYPOPSTACK (1); \
+ YYPOPSTACK (1); \]b4_lac_if([[
+ YY_LAC_DISCARD ("YYBACKUP"); \]])[
goto yybackup; \
} \
else \
#ifndef YYMAXDEPTH
# define YYMAXDEPTH ]b4_stack_depth_max[
+#endif]b4_lac_if([[
+
+/* Establish the initial context for the current lookahead if no initial
+ context is currently established.
+
+ We define a context as a snapshot of the parser stacks. We define
+ the initial context for a lookahead as the context in which the
+ parser initially examines that lookahead in order to select a
+ syntactic action. Thus, if the lookahead eventually proves
+ syntactically unacceptable (possibly in a later context reached via a
+ series of reductions), the initial context can be used to determine
+ the exact set of tokens that would be syntactically acceptable in the
+ lookahead's place. Moreover, it is the context after which any
+ further semantic actions would be erroneous because they would be
+ determined by a syntactically unacceptable token.
+
+ YY_LAC_ESTABLISH should be invoked when a reduction is about to be
+ performed in an inconsistent state (which, for the purposes of LAC,
+ includes consistent states that don't know they're consistent because
+ their default reductions have been disabled). Iff there is a
+ lookahead token, it should also be invoked before reporting a syntax
+ error. This latter case is for the sake of the debugging output.
+
+ For parse.lac=full, the implementation of YY_LAC_ESTABLISH is as
+ follows. If no initial context is currently established for the
+ current lookahead, then check if that lookahead can eventually be
+ shifted if syntactic actions continue from the current context.
+ Report a syntax error if it cannot. */
+#define YY_LAC_ESTABLISH \
+do { \
+ if (!yy_lac_established) \
+ { \
+ YYDPRINTF ((stderr, \
+ "LAC: initial context established for %s\n", \
+ yytname[yytoken])); \
+ yy_lac_established = 1; \
+ { \
+ int yy_lac_status = \
+ yy_lac (yyssp, yytoken); \
+ if (yy_lac_status == 2) \
+ goto yyexhaustedlab; \
+ if (yy_lac_status == 1) \
+ goto yyerrlab; \
+ } \
+ } \
+} while (YYID (0))
+
+/* Discard any previous initial lookahead context because of Event,
+ which may be a lookahead change or an invalidation of the currently
+ established initial context for the current lookahead.
+
+ The most common example of a lookahead change is a shift. An example
+ of both cases is syntax error recovery. That is, a syntax error
+ occurs when the lookahead is syntactically erroneous for the
+ currently established initial context, so error recovery manipulates
+ the parser stacks to try to find a new initial context in which the
+ current lookahead is syntactically acceptable. If it fails to find
+ such a context, it discards the lookahead. */
+#if YYDEBUG
+# define YY_LAC_DISCARD(Event) \
+do { \
+ if (yy_lac_established) \
+ { \
+ if (yydebug) \
+ YYFPRINTF (stderr, "LAC: initial context discarded due to " \
+ Event "\n"); \
+ yy_lac_established = 0; \
+ } \
+} while (YYID (0))
+#else
+# define YY_LAC_DISCARD(Event) yy_lac_established = 0
#endif
-\f
+/* Given the stack whose top is *YYSSP, return 0 iff YYTOKEN can
+ eventually (after perhaps some reductions) be shifted, and return 1
+ if not. Return 2 if memory is exhausted. */
+static int
+yy_lac (yytype_int16 *yyssp, int yytoken)
+{
+ yytype_int16 *yyes_prev = yyssp;
+ yytype_int16 yyes@{]b4_percent_define_get([[parse.lac.es-capacity]])[@};
+ yytype_int16 *yyesp = yyes_prev;
+ YYDPRINTF ((stderr, "LAC: checking lookahead %s:", yytname[yytoken]));
+ if (yytoken == YYUNDEFTOK)
+ {
+ YYDPRINTF ((stderr, " Always Err\n"));
+ return 1;
+ }
+ while (1)
+ {
+ int yyrule = yypact[*yyesp];
+ if (yypact_value_is_default (yyrule)
+ || (yyrule += yytoken) < 0 || YYLAST < yyrule
+ || yycheck[yyrule] != yytoken)
+ {
+ yyrule = yydefact[*yyesp];
+ if (yyrule == 0)
+ {
+ YYDPRINTF ((stderr, " Err\n"));
+ return 1;
+ }
+ }
+ else
+ {
+ yyrule = yytable[yyrule];
+ if (yytable_value_is_error (yyrule))
+ {
+ YYDPRINTF ((stderr, " Err\n"));
+ return 1;
+ }
+ if (0 < yyrule)
+ {
+ YYDPRINTF ((stderr, " S%d\n", yyrule));
+ return 0;
+ }
+ yyrule = -yyrule;
+ }
+ {
+ YYSIZE_T yylen = yyr2[yyrule];
+ YYDPRINTF ((stderr, " R%d", yyrule - 1));
+ if (yyesp != yyes_prev)
+ {
+ YYSIZE_T yysize = yyesp - yyes + 1;
+ if (yylen < yysize)
+ {
+ yyesp -= yylen;
+ yylen = 0;
+ }
+ else
+ {
+ yylen -= yysize;
+ yyesp = yyes_prev;
+ }
+ }
+ if (yylen)
+ yyesp = yyes_prev -= yylen;
+ }
+ {
+ int yystate;
+ {
+ int yylhs = yyr1[yyrule] - YYNTOKENS;
+ yystate = yypgoto[yylhs] + *yyesp;
+ if (yystate < 0 || YYLAST < yystate
+ || yycheck[yystate] != *yyesp)
+ yystate = yydefgoto[yylhs];
+ else
+ yystate = yytable[yystate];
+ }
+ if (yyesp == yyes_prev)
+ {
+ yyesp = yyes;
+ *yyesp = yystate;
+ }
+ else
+ {
+ if (yyesp == yyes + (sizeof yyes / sizeof *yyes) - 1)
+ {
+ YYDPRINTF ((stderr, " (max stack size exceeded)\n"));
+ return 2;
+ }
+ *++yyesp = yystate;
+ }
+ YYDPRINTF ((stderr, " G%d", *yyesp));
+ }
+ }
+}]])[
+
#if YYERROR_VERBOSE
# endif
/* Copy into *YYMSG, which is of size *YYMSG_ALLOC, an error message
- about the unexpected token YYTOKEN while in state YYSTATE.
+ about the unexpected token YYTOKEN for the state stack whose top is
+ YYSSP.]b4_lac_if([[ In order to see if a particular token T is a
+ valid looakhead, invoke yy_lac (YYSSP, T).]])[
Return 0 if *YYMSG was successfully written. Return 1 if *YYMSG is
not large enough to hold the message. In that case, also set
*YYMSG_ALLOC to the required number of bytes. Return 2 if the
- required number of bytes is too large to store. */
+ required number of bytes is too large to store]b4_lac_if([[ or if
+ yy_lac returned 2]])[. */
static int
yysyntax_error (YYSIZE_T *yymsg_alloc, char **yymsg,
- int yystate, int yytoken)
+ yytype_int16 *yyssp, int yytoken)
{
YYSIZE_T yysize0 = yytnamerr (0, yytname[yytoken]);
YYSIZE_T yysize = yysize0;
- 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.
+ action, or user semantic action that manipulated yychar.]b4_lac_if([[
+ In the first two cases, it might appear that the current syntax
+ error should have been detected in the previous state when yy_lac
+ was invoked. However, at that time, there might have been a
+ different syntax error that discarded a different initial context
+ during error recovery, leaving behind the current lookahead.]], [[
- 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
(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.
+ accepted due to an error action in a later state.]])[
*/
if (yytoken != YYEMPTY)
{
- int yyn = yypact[yystate];
+ int yyn = yypact[*yyssp];]b4_lac_if([[
+ YYDPRINTF ((stderr, "Constructing syntax error message\n"));]])[
yyarg[yycount++] = yytname[yytoken];
if (!yypact_value_is_default (yyn))
- {
+ {]b4_lac_if([], [[
/* 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;
- int yyx;
+ int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;]])[
+ int yyx;]b4_lac_if([[
+
+ for (yyx = 0; yyx < YYNTOKENS; ++yyx)
+ if (yyx != YYTERROR && yyx != YYUNDEFTOK)
+ {
+ {
+ int yy_lac_status = yy_lac (yyssp, yyx);
+ if (yy_lac_status == 2)
+ return 2;
+ if (yy_lac_status == 1)
+ continue;
+ }]], [[
+
for (yyx = yyxbegin; yyx < yyxend; ++yyx)
if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR
&& !yytable_value_is_error (yytable[yyx + yyn]))
- {
+ {]])[
if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)
{
yycount = 1;
return 2;
yysize = yysize1;
}
- }
+ }]b4_lac_if([[
+# if YYDEBUG
+ else if (yydebug)
+ YYFPRINTF (stderr, "No expected tokens.\n");
+# endif]])[
}
switch (yycount)
{
-#define YYCASE_(N, S) \
+# define YYCASE_(N, S) \
case N: \
yyformat = S; \
break
YYCASE_(3, YY_("syntax error, unexpected %s, expecting %s or %s"));
YYCASE_(4, YY_("syntax error, unexpected %s, expecting %s or %s or %s"));
YYCASE_(5, YY_("syntax error, unexpected %s, expecting %s or %s or %s or %s"));
-#undef YYCASE_
+# undef YYCASE_
}
yysize1 = yysize + yystrlen (yyformat);
return 0;
}
#endif /* YYERROR_VERBOSE */
-\f
]b4_yydestruct_generate([b4_c_function_def])b4_push_if([], [[
YYLTYPE yypushed_loc = yylloc;]])
])],
[b4_declare_parser_state_variables
-])[
+])b4_lac_if([[
+ int yy_lac_established = 0;]])[
int yyn;
int yyresult;
/* Lookahead token as an internal (translated) token number. */
/* If the proper action on seeing token YYTOKEN is to reduce or to
detect an error, take that action. */
yyn += yytoken;
- if (yyn < 0 || YYLAST < yyn || yycheck[yyn] != yytoken)
- goto yydefault;
+ if (yyn < 0 || YYLAST < yyn || yycheck[yyn] != yytoken)]b4_lac_if([[
+ {
+ YY_LAC_ESTABLISH;
+ goto yydefault;
+ }]], [[
+ goto yydefault;]])[
yyn = yytable[yyn];
if (yyn <= 0)
{
if (yytable_value_is_error (yyn))
- goto yyerrlab;
+ goto yyerrlab;]b4_lac_if([[
+ YY_LAC_ESTABLISH;]])[
yyn = -yyn;
goto yyreduce;
}
YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
/* Discard the shifted token. */
- yychar = YYEMPTY;
+ yychar = YYEMPTY;]b4_lac_if([[
+ YY_LAC_DISCARD ("shift");]])[
yystate = yyn;
*++yyvsp = yylval;
]b4_locations_if(
[[ /* Default location. */
YYLLOC_DEFAULT (yyloc, (yylsp - yylen), yylen);]])[
- YY_REDUCE_PRINT (yyn);
+ YY_REDUCE_PRINT (yyn);]b4_lac_if([[
+ {
+ int yychar_backup = yychar;
+ switch (yyn)
+ {
+ ]b4_user_actions[
+ default: break;
+ }
+ if (yychar_backup != yychar)
+ YY_LAC_DISCARD ("yychar change");
+ }]], [[
switch (yyn)
{
]b4_user_actions[
default: break;
- }
+ }]])[
/* User semantic actions sometimes alter yychar, and that requires
that yytoken be updated with the new translation. We take the
approach of translating immediately before every use of yytoken.
#if ! YYERROR_VERBOSE
yyerror (]b4_yyerror_args[YY_("syntax error"));
#else
-# define YYSYNTAX_ERROR yysyntax_error (&yymsg_alloc, &yymsg, yystate, \
+# define YYSYNTAX_ERROR yysyntax_error (&yymsg_alloc, &yymsg, yyssp, \
yytoken)
{
char const *yymsgp = YY_("syntax error");
- int yysyntax_error_status = YYSYNTAX_ERROR;
+ int yysyntax_error_status;]b4_lac_if([[
+ if (yychar != YYEMPTY)
+ YY_LAC_ESTABLISH;]])[
+ yysyntax_error_status = YYSYNTAX_ERROR;
if (yysyntax_error_status == 0)
yymsgp = yymsg;
else if (yysyntax_error_status == 1)
YYPOPSTACK (1);
yystate = *yyssp;
YY_STACK_PRINT (yyss, yyssp);
- }
+ }]b4_lac_if([[
+
+ /* If the stack popping above didn't lose the initial context for the
+ current lookahead token, the shift below will for sure. */
+ YY_LAC_DISCARD ("error recovery");]])[
*++yyvsp = yylval;
]b4_locations_if([[
yyresult = 1;
goto yyreturn;
-#if !defined(yyoverflow) || YYERROR_VERBOSE
+#if ]b4_lac_if([[1]], [[!defined(yyoverflow) || YYERROR_VERBOSE]])[
/*-------------------------------------------------.
| yyexhaustedlab -- memory exhaustion comes here. |
`-------------------------------------------------*/
projects / bison.git / blobdiff