/* Input parser for Bison
Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000-2003, 2005-2007,
2009-2012 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
#include "system.h"
#include <quote.h>
#include "complain.h"
#include "conflicts.h"
#include "files.h"
#include "getargs.h"
#include "gram.h"
#include "muscle-tab.h"
#include "reader.h"
#include "symlist.h"
#include "symtab.h"
#include "scan-gram.h"
#include "scan-code.h"
static void prepare_percent_define_front_end_variables (void);
static void check_and_convert_grammar (void);
static symbol_list *grammar = NULL;
static bool start_flag = false;
merger_list *merge_functions;
/* Was %union seen? */
bool union_seen = false;
/* Was a tag seen? */
bool tag_seen = false;
/* Should rules have a default precedence? */
bool default_prec = true;
/*-----------------------.
| Set the start symbol. |
`-----------------------*/
void
grammar_start_symbol_set (symbol *sym, location loc)
{
if (start_flag)
complain_at (loc, _("multiple %s declarations"), "%start");
else
{
start_flag = true;
startsymbol = sym;
startsymbol_location = loc;
}
}
/*------------------------------------------------------------------------.
| Return the merger index for a merging function named NAME. Records the |
| function, if new, in MERGER_LIST. |
`------------------------------------------------------------------------*/
static int
get_merge_function (uniqstr name)
{
merger_list *syms;
merger_list head;
int n;
if (! glr_parser)
return 0;
head.next = merge_functions;
for (syms = &head, n = 1; syms->next; syms = syms->next, n += 1)
if (UNIQSTR_EQ (name, syms->next->name))
break;
if (syms->next == NULL)
{
syms->next = xmalloc (sizeof syms->next[0]);
syms->next->name = uniqstr_new (name);
/* After all symbol type declarations have been parsed, packgram invokes
record_merge_function_type to set the type. */
syms->next->type = NULL;
syms->next->next = NULL;
merge_functions = head.next;
}
return n;
}
/*-------------------------------------------------------------------------.
| For the existing merging function with index MERGER, record the result |
| type as TYPE as required by the lhs of the rule whose %merge declaration |
| is at DECLARATION_LOC. |
`-------------------------------------------------------------------------*/
static void
record_merge_function_type (int merger, uniqstr type, location declaration_loc)
{
int merger_find;
merger_list *merge_function;
if (merger <= 0)
return;
if (type == NULL)
type = uniqstr_new ("");
merger_find = 1;
for (merge_function = merge_functions;
merge_function != NULL && merger_find != merger;
merge_function = merge_function->next)
merger_find += 1;
aver (merge_function != NULL && merger_find == merger);
if (merge_function->type != NULL && !UNIQSTR_EQ (merge_function->type, type))
{
unsigned indent = 0;
complain_at_indent (declaration_loc, &indent,
_("result type clash on merge function %s: "
"<%s> != <%s>"),
quote (merge_function->name), type,
merge_function->type);
indent += SUB_INDENT;
complain_at_indent (merge_function->type_declaration_location, &indent,
_("previous declaration"));
}
merge_function->type = uniqstr_new (type);
merge_function->type_declaration_location = declaration_loc;
}
/*--------------------------------------.
| Free all merge-function definitions. |
`--------------------------------------*/
void
free_merger_functions (void)
{
merger_list *L0 = merge_functions;
while (L0)
{
merger_list *L1 = L0->next;
free (L0);
L0 = L1;
}
}
/*-------------------------------------------------------------------.
| Parse the input grammar into a one symbol_list structure. Each |
| rule is represented by a sequence of symbols: the left hand side |
| followed by the contents of the right hand side, followed by a |
| null pointer instead of a symbol to terminate the rule. The next |
| symbol is the lhs of the following rule. |
| |
| All actions are copied out, labelled by the rule number they apply |
| to. |
`-------------------------------------------------------------------*/
/* The (currently) last symbol of GRAMMAR. */
static symbol_list *grammar_end = NULL;
/* Append SYM to the grammar. */
static symbol_list *
grammar_symbol_append (symbol *sym, location loc)
{
symbol_list *p = symbol_list_sym_new (sym, loc);
if (grammar_end)
grammar_end->next = p;
else
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;
return p;
}
static void
assign_named_ref (symbol_list *p, named_ref *name)
{
symbol *sym = p->content.sym;
if (name->id == sym->tag)
{
warn_at (name->loc,
_("duplicated symbol name for %s ignored"),
quote (sym->tag));
named_ref_free (name);
}
else
p->named_ref = name;
}
/* The rule currently being defined, and the previous rule.
CURRENT_RULE points to the first LHS of the current rule, while
PREVIOUS_RULE_END points to the *end* of the previous rule (NULL). */
static symbol_list *current_rule = NULL;
static symbol_list *previous_rule_end = NULL;
/*----------------------------------------------.
| Create a new rule for LHS in to the GRAMMAR. |
`----------------------------------------------*/
void
grammar_current_rule_begin (symbol *lhs, location loc,
named_ref *lhs_name)
{
symbol_list* p;
/* Start a new rule and record its lhs. */
++nrules;
previous_rule_end = grammar_end;
p = grammar_symbol_append (lhs, loc);
if (lhs_name)
assign_named_ref (p, named_ref_copy (lhs_name));
current_rule = grammar_end;
/* Mark the rule's lhs as a nonterminal if not already so. */
if (lhs->class == unknown_sym)
{
lhs->class = nterm_sym;
lhs->number = nvars;
++nvars;
}
else if (lhs->class == token_sym)
complain_at (loc, _("rule given for %s, which is a token"), lhs->tag);
}
/*----------------------------------------------------------------------.
| A symbol should be used if either: |
| 1. It has a destructor. |
| 2. The symbol is a mid-rule symbol (i.e., the generated LHS |
| replacing a mid-rule action) that was assigned to or used, as in |
| "exp: { $$ = 1; } { $$ = $1; }". |
`----------------------------------------------------------------------*/
static bool
symbol_should_be_used (symbol_list const *s, bool *midrule_warning)
{
if (symbol_destructor_get (s->content.sym)->code)
return true;
if ((s->midrule && s->midrule->action_props.is_value_used)
|| (s->midrule_parent_rule
&& symbol_list_n_get (s->midrule_parent_rule,
s->midrule_parent_rhs_index)
->action_props.is_value_used))
{
*midrule_warning = true;
return true;
}
return false;
}
/*----------------------------------------------------------------.
| 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
is allowed to shoot herself in the foot.
Don't worry about the default action if $$ is untyped, since $$'s
value can't be used. */
if (!r->action_props.code && r->content.sym->type_name)
{
symbol *first_rhs = r->next->content.sym;
/* If $$ is being set in default way, report if any type mismatch. */
if (first_rhs)
{
char const *lhs_type = r->content.sym->type_name;
const char *rhs_type =
first_rhs->type_name ? first_rhs->type_name : "";
if (!UNIQSTR_EQ (lhs_type, rhs_type))
warn_at (r->location,
_("type clash on default action: <%s> != <%s>"),
lhs_type, rhs_type);
}
/* Warn if there is no default for $$ but we need one. */
else
warn_at (r->location,
_("empty rule for typed nonterminal, and no action"));
}
/* Check that symbol values that should be used are in fact used. */
{
symbol_list const *l = r;
int n = 0;
for (; l && l->content.sym; l = l->next, ++n)
{
bool midrule_warning = false;
if (!l->action_props.is_value_used
&& symbol_should_be_used (l, &midrule_warning)
/* The default action, $$ = $1, `uses' both. */
&& (r->action_props.code || (n != 0 && n != 1)))
{
void (*warn_at_ptr)(location, char const*, ...) =
midrule_warning ? midrule_value_at : warn_at;
if (n)
warn_at_ptr (l->location, _("unused value: $%d"), n);
else
warn_at_ptr (l->location, _("unset value: $$"));
}
}
}
/* See comments in grammar_current_rule_prec_set for how POSIX
mandates this complaint. It's only for identifiers, so skip
it for char literals and strings, which are always tokens. */
if (r->ruleprec
&& r->ruleprec->tag[0] != '\'' && r->ruleprec->tag[0] != '"'
&& !r->ruleprec->declared && !r->ruleprec->prec)
warn_at (r->location, _("token for %%prec is not defined: %s"),
r->ruleprec->tag);
}
/*-------------------------------------.
| End the currently being grown rule. |
`-------------------------------------*/
void
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;
}
/*-------------------------------------------------------------------.
| The previous action turns out the be a mid-rule action. Attach it |
| to the current rule, i.e., create a dummy symbol, attach it this |
| mid-rule action, and append this dummy nonterminal to the current |
| rule. |
`-------------------------------------------------------------------*/
void
grammar_midrule_action (void)
{
/* Since the action was written out with this rule's number, we must
give the new rule this number by inserting the new rule before
it. */
/* Make a DUMMY nonterminal, whose location is that of the midrule
action. Create the MIDRULE. */
location dummy_location = current_rule->action_props.location;
symbol *dummy = dummy_symbol_get (dummy_location);
symbol_list *midrule = symbol_list_sym_new (dummy, dummy_location);
/* Remember named_ref of previous action. */
named_ref *action_name = current_rule->action_props.named_ref;
/* Make a new rule, whose body is empty, before the current one, so
that the action just read can belong to it. */
++nrules;
++nritems;
/* Attach its location and actions to that of the DUMMY. */
midrule->location = dummy_location;
code_props_rule_action_init (&midrule->action_props,
current_rule->action_props.code,
current_rule->action_props.location,
midrule, 0);
code_props_none_init (¤t_rule->action_props);
if (previous_rule_end)
previous_rule_end->next = midrule;
else
grammar = midrule;
/* End the dummy's rule. */
midrule->next = symbol_list_sym_new (NULL, dummy_location);
midrule->next->next = current_rule;
previous_rule_end = midrule->next;
/* Insert the dummy nonterminal replacing the midrule action into
the current rule. Bind it to its dedicated rule. */
grammar_current_rule_symbol_append (dummy, dummy_location,
action_name);
grammar_end->midrule = midrule;
midrule->midrule_parent_rule = current_rule;
midrule->midrule_parent_rhs_index = symbol_list_length (current_rule->next);
}
/* Set the precedence symbol of the current rule to PRECSYM. */
void
grammar_current_rule_prec_set (symbol *precsym, location loc)
{
/* POSIX says that any identifier is a nonterminal if it does not
appear on the LHS of a grammar rule and is not defined by %token
or by one of the directives that assigns precedence to a token. We
ignore this here because the only kind of identifier that POSIX
allows to follow a %prec is a token and because assuming it's a
token now can produce more logical error messages. Nevertheless,
grammar_rule_check does obey what we believe is the real intent of
POSIX here: that an error be reported for any identifier that
appears after %prec but that is not defined separately as a
token. */
symbol_class_set (precsym, token_sym, loc, false);
if (current_rule->ruleprec)
complain_at (loc, _("only one %s allowed per rule"), "%prec");
current_rule->ruleprec = precsym;
}
/* Attach dynamic precedence DPREC to the current rule. */
void
grammar_current_rule_dprec_set (int dprec, location loc)
{
if (! glr_parser)
warn_at (loc, _("%s affects only GLR parsers"), "%dprec");
if (dprec <= 0)
complain_at (loc, _("%s must be followed by positive number"), "%dprec");
else if (current_rule->dprec != 0)
complain_at (loc, _("only one %s allowed per rule"), "%dprec");
current_rule->dprec = dprec;
}
/* Attach a merge function NAME with argument type TYPE to current
rule. */
void
grammar_current_rule_merge_set (uniqstr name, location loc)
{
if (! glr_parser)
warn_at (loc, _("%s affects only GLR parsers"), "%merge");
if (current_rule->merger != 0)
complain_at (loc, _("only one %s allowed per rule"), "%merge");
current_rule->merger = get_merge_function (name);
current_rule->merger_declaration_location = loc;
}
/* Attach SYM to the current rule. If needed, move the previous
action as a mid-rule action. */
void
grammar_current_rule_symbol_append (symbol *sym, location loc,
named_ref *name)
{
symbol_list *p;
if (current_rule->action_props.code)
grammar_midrule_action ();
p = grammar_symbol_append (sym, loc);
if (name)
assign_named_ref(p, name);
}
/* Attach an ACTION to the current rule. */
void
grammar_current_rule_action_append (const char *action, location loc,
named_ref *name)
{
if (current_rule->action_props.code)
grammar_midrule_action ();
/* After all symbol declarations have been parsed, packgram invokes
code_props_translate_code. */
code_props_rule_action_init (¤t_rule->action_props, action, loc,
current_rule, name);
}
/*---------------------------------------------------------------.
| Convert the rules into the representation using RRHS, RLHS and |
| RITEM. |
`---------------------------------------------------------------*/
static void
packgram (void)
{
unsigned int itemno = 0;
rule_number ruleno = 0;
symbol_list *p = grammar;
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)
{
int rule_length = 0;
symbol *ruleprec = p->ruleprec;
record_merge_function_type (p->merger, p->content.sym->type_name,
p->merger_declaration_location);
rules[ruleno].user_number = ruleno;
rules[ruleno].number = ruleno;
rules[ruleno].lhs = p->content.sym;
rules[ruleno].rhs = ritem + itemno;
rules[ruleno].prec = NULL;
rules[ruleno].dprec = p->dprec;
rules[ruleno].merger = p->merger;
rules[ruleno].precsym = NULL;
rules[ruleno].location = p->location;
rules[ruleno].useful = true;
rules[ruleno].action = p->action_props.code;
rules[ruleno].action_location = p->action_props.location;
/* If the midrule's $$ is set or its $n is used, remove the `$' from the
symbol name so that it's a user-defined symbol so that the default
%destructor and %printer apply. */
if (p->midrule_parent_rule
&& (p->action_props.is_value_used
|| symbol_list_n_get (p->midrule_parent_rule,
p->midrule_parent_rhs_index)
->action_props.is_value_used))
p->content.sym->tag += 1;
/* 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->content.sym; p = p->next)
{
++rule_length;
/* Don't allow rule_length == INT_MAX, since that might
cause confusion with strtol if INT_MAX == LONG_MAX. */
if (rule_length == INT_MAX)
fatal_at (rules[ruleno].location, _("rule is too long"));
/* item_number = symbol_number.
But the former needs to contain more: negative rule numbers. */
ritem[itemno++] =
symbol_number_as_item_number (p->content.sym->number);
/* A rule gets by default the precedence and associativity
of its last token. */
if (p->content.sym->class == token_sym && default_prec)
rules[ruleno].prec = p->content.sym;
}
/* If this rule has a %prec,
the specified symbol's precedence replaces the default. */
if (ruleprec)
{
rules[ruleno].precsym = ruleprec;
rules[ruleno].prec = ruleprec;
}
/* An item ends by the rule number (negated). */
ritem[itemno++] = rule_number_as_item_number (ruleno);
aver (itemno < ITEM_NUMBER_MAX);
++ruleno;
aver (ruleno < RULE_NUMBER_MAX);
if (p)
p = p->next;
}
aver (itemno == nritems);
if (trace_flag & trace_sets)
ritem_print (stderr);
}
/*------------------------------------------------------------------.
| Read in the grammar specification and record it in the format |
| described in gram.h. All actions are copied into ACTION_OBSTACK, |
| in each case forming the body of a C function (YYACTION) which |
| contains a switch statement to decide which action to execute. |
`------------------------------------------------------------------*/
void
reader (void)
{
/* Initialize the symbol table. */
symbols_new ();
/* Construct the accept symbol. */
accept = symbol_get ("$accept", empty_location);
accept->class = nterm_sym;
accept->number = nvars++;
/* Construct the error token */
errtoken = symbol_get ("error", empty_location);
errtoken->class = token_sym;
errtoken->number = ntokens++;
/* Construct a token that represents all undefined literal tokens.
It is always token number 2. */
undeftoken = symbol_get ("$undefined", empty_location);
undeftoken->class = token_sym;
undeftoken->number = ntokens++;
gram_in = xfopen (grammar_file, "r");
gram__flex_debug = trace_flag & trace_scan;
gram_debug = trace_flag & trace_parse;
gram_scanner_initialize ();
gram_parse ();
prepare_percent_define_front_end_variables ();
if (! complaint_issued)
check_and_convert_grammar ();
xfclose (gram_in);
}
static void
prepare_percent_define_front_end_variables (void)
{
/* Set %define front-end variable defaults. */
muscle_percent_define_default ("lr.keep-unreachable-states", "false");
{
char *lr_type;
/* IELR would be a better default, but LALR is historically the
default. */
muscle_percent_define_default ("lr.type", "lalr");
lr_type = muscle_percent_define_get ("lr.type");
if (0 != strcmp (lr_type, "canonical-lr"))
muscle_percent_define_default ("lr.default-reductions", "most");
else
muscle_percent_define_default ("lr.default-reductions", "accepting");
free (lr_type);
}
/* Check %define front-end variables. */
{
static char const * const values[] = {
"lr.type", "lalr", "ielr", "canonical-lr", NULL,
"lr.default-reductions", "most", "consistent", "accepting", NULL,
NULL
};
muscle_percent_define_check_values (values);
}
}
/*-------------------------------------------------------------.
| 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"));
/* If the user did not define her ENDTOKEN, do it now. */
if (!endtoken)
{
endtoken = symbol_get ("$end", empty_location);
endtoken->class = token_sym;
endtoken->number = 0;
/* Value specified by POSIX. */
endtoken->user_token_number = 0;
}
/* Report any undefined symbols and consider them nonterminals. */
symbols_check_defined ();
/* Find the start symbol if no %start. */
if (!start_flag)
{
symbol_list *node;
for (node = grammar;
node != NULL && symbol_is_dummy (node->content.sym);
node = node->next)
{
for (node = node->next;
node != NULL && node->content.sym != NULL;
node = node->next)
;
}
aver (node != NULL);
grammar_start_symbol_set (node->content.sym,
node->content.sym->location);
}
/* Insert the initial rule, whose line is that of the first rule
(not that of the start symbol):
accept: %start EOF. */
{
symbol_list *p = symbol_list_sym_new (accept, empty_location);
p->location = grammar->location;
p->next = symbol_list_sym_new (startsymbol, empty_location);
p->next->next = symbol_list_sym_new (endtoken, empty_location);
p->next->next->next = symbol_list_sym_new (NULL, empty_location);
p->next->next->next->next = grammar;
nrules += 1;
nritems += 3;
grammar = p;
}
aver (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars);
/* Assign the symbols their symbol numbers. Write #defines for the
token symbols into FDEFINES if requested. */
symbols_pack ();
/* Scan rule actions after invoking symbol_check_alias_consistency (in
symbols_pack above) so that token types are set correctly before the rule
action type checking.
Before invoking grammar_rule_check (in packgram below) on any rule, make
sure all actions have already been scanned in order to set `used' flags.
Otherwise, checking that a midrule's $$ should be set will not always work
properly because the check must forward-reference the midrule's parent
rule. For the same reason, all the `used' flags must be set before
checking whether to remove `$' from any midrule symbol name (also in
packgram). */
{
symbol_list *sym;
for (sym = grammar; sym; sym = sym->next)
code_props_translate_code (&sym->action_props);
}
/* Convert the grammar into the format described in gram.h. */
packgram ();
/* The grammar as a symbol_list is no longer needed. */
symbol_list_free (grammar);
}