/* Input parser for Bison
Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002, 2003,
- 2005 Free Software Foundation, Inc.
+ 2005, 2006 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
#include "getargs.h"
#include "gram.h"
#include "muscle_tab.h"
-#include "output.h"
#include "reader.h"
#include "symlist.h"
#include "symtab.h"
+static void check_and_convert_grammar (void);
+
static symbol_list *grammar = NULL;
static bool start_flag = false;
merger_list *merge_functions;
static symbol_list *grammar_end = NULL;
/* Append SYM to the grammar. */
-void
+static void
grammar_symbol_append (symbol *sym, location loc)
{
symbol_list *p = symbol_list_new (sym, loc);
grammar = p;
grammar_end = p;
+
+ /* A null SYM stands for an end of rule; it is not an actual
+ part of it. */
+ if (sym)
+ ++nritems;
}
/* The rule currently being defined, and the previous rule.
`----------------------------------------------*/
void
-grammar_rule_begin (symbol *lhs, location loc)
+grammar_current_rule_begin (symbol *lhs, location loc)
{
if (!start_flag)
{
/* Start a new rule and record its lhs. */
++nrules;
- ++nritems;
-
previous_rule_end = grammar_end;
grammar_symbol_append (lhs, loc);
current_rule = grammar_end;
}
-/*------------------------------------------------------------------.
-| Check that the last rule (CURRENT_RULE) is properly defined. For |
-| instance, there should be no type clash on the default action. |
-`------------------------------------------------------------------*/
+/*----------------------------------------------------------------------.
+| A symbol should be used if it has a destructor, or if it is a |
+| mid-rule symbol (i.e., the generated LHS replacing a mid-rule |
+| action) that was assigned to, as in "exp: { $$ = 1; } { $$ = $1; }". |
+`----------------------------------------------------------------------*/
-static void
-grammar_current_rule_check (void)
+static bool
+symbol_should_be_used (symbol_list const *s)
{
- symbol *lhs = current_rule->sym;
- char const *lhs_type = lhs->type_name;
+ return (s->sym->destructor
+ || (s->midrule && s->midrule->used));
+}
+/*----------------------------------------------------------------.
+| Check that the rule R is properly defined. For instance, there |
+| should be no type clash on the default action. |
+`----------------------------------------------------------------*/
+
+static void
+grammar_rule_check (const symbol_list *r)
+{
/* Type check.
If there is an action, then there is nothing we can do: the user
Don't worry about the default action if $$ is untyped, since $$'s
value can't be used. */
- if (!current_rule->action && lhs_type)
+ if (!r->action && r->sym->type_name)
{
- symbol *first_rhs = current_rule->next->sym;
+ symbol *first_rhs = r->next->sym;
/* If $$ is being set in default way, report if any type mismatch. */
if (first_rhs)
{
+ char const *lhs_type = r->sym->type_name;
const char *rhs_type =
first_rhs->type_name ? first_rhs->type_name : "";
if (!UNIQSTR_EQ (lhs_type, rhs_type))
- warn_at (current_rule->location,
+ warn_at (r->location,
_("type clash on default action: <%s> != <%s>"),
lhs_type, rhs_type);
}
/* Warn if there is no default for $$ but we need one. */
else
- warn_at (current_rule->location,
+ warn_at (r->location,
_("empty rule for typed nonterminal, and no action"));
}
- /* Check that all the symbol values are used. */
- if (typed)
- {
- symbol_list *l = current_rule;
- int n = 1;
- for (l = current_rule->next; l && l->sym; l = l->next, ++n)
- /* The default action `uses' $1. */
- if (! (!current_rule->action && n == 1)
- && l->sym->type_name && !l->used)
- warn_at (current_rule->location, _("unused value: $%d"), n);
- }
+ /* Check that symbol values that should be used are in fact used. */
+ {
+ symbol_list const *l = r;
+ int n = 0;
+ for (; l && l->sym; l = l->next, ++n)
+ if (! (l->used
+ || !symbol_should_be_used (l)
+ /* The default action, $$ = $1, `uses' both. */
+ || (!r->action && (n == 0 || n == 1))))
+ {
+ if (n)
+ warn_at (r->location, _("unused value: $%d"), n);
+ else
+ warn_at (r->location, _("unset value: $$"));
+ }
+ }
}
`-------------------------------------*/
void
-grammar_rule_end (location loc)
+grammar_current_rule_end (location loc)
{
/* Put an empty link in the list to mark the end of this rule */
grammar_symbol_append (NULL, grammar_end->location);
current_rule->location = loc;
- grammar_current_rule_check ();
+ grammar_rule_check (current_rule);
}
midrule->action = current_rule->action;
midrule->action_location = dummy_location;
current_rule->action = NULL;
+ /* If $$ was used in the action, the LHS of the enclosing rule was
+ incorrectly flagged as used. */
+ midrule->used = current_rule->used;
+ current_rule->used = false;
if (previous_rule_end)
previous_rule_end->next = midrule;
grammar = midrule;
/* End the dummy's rule. */
- previous_rule_end = symbol_list_new (NULL, dummy_location);
- previous_rule_end->next = current_rule;
+ midrule->next = symbol_list_new (NULL, dummy_location);
+ grammar_rule_check (midrule);
+ midrule->next->next = current_rule;
- midrule->next = previous_rule_end;
+ previous_rule_end = midrule->next;
/* Insert the dummy nonterminal replacing the midrule action into
- the current rule. */
+ the current rule. Bind it to its dedicated rule. */
grammar_current_rule_symbol_append (dummy, dummy_location);
+ grammar_end->midrule = midrule;
}
/* Set the precedence symbol of the current rule to PRECSYM. */
{
if (current_rule->action)
grammar_midrule_action ();
- ++nritems;
grammar_symbol_append (sym, loc);
}
-/* Attach an ACTION to the current rule. If needed, move the previous
- action as a mid-rule action. */
+/* Attach an ACTION to the current rule. */
void
grammar_current_rule_action_append (const char *action, location loc)
{
- if (current_rule->action)
- grammar_midrule_action ();
+ /* There's no need to invoke grammar_midrule_action here, since the
+ scanner already did it if necessary. */
current_rule->action = action;
current_rule->action_location = loc;
}
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)
p = p->next;
}
- if (itemno != nritems)
- abort ();
+ assert (itemno == nritems);
if (trace_flag & trace_sets)
ritem_print (stderr);
scanner_initialize ();
gram_parse ();
- /* If something went wrong during the parsing, don't try to
- continue. */
- if (complaint_issued)
- return;
+ if (! complaint_issued)
+ check_and_convert_grammar ();
- /* Grammar has been read. Do some checking */
+ xfclose (gram_in);
+}
+
+
+/*-------------------------------------------------------------.
+| Check the grammar that has just been read, and convert it to |
+| internal form. |
+`-------------------------------------------------------------*/
+
+static void
+check_and_convert_grammar (void)
+{
+ /* Grammar has been read. Do some checking. */
if (nrules == 0)
fatal (_("no rules in the input grammar"));
endtoken->user_token_number = 0;
}
- /* Insert the initial rule, which line is that of the first rule
+ /* Insert the initial rule, whose line is that of the first rule
(not that of the start symbol):
accept: %start EOF. */
grammar = p;
}
- if (! (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars))
- abort ();
-
- xfclose (gram_in);
+ assert (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars);
/* Assign the symbols their symbol numbers. Write #defines for the
token symbols into FDEFINES if requested. */
projects / bison.git / blobdiff