* doc/bison.texinfo (Stack Overflow): xref to Recursion.

[bison.git] / src / gram.h

diff --git a/src/gram.h b/src/gram.h
index 021061d21e2860d8caab3e993ebc18c62bb70cd3..de782f7d646ef570f628230f767cb1d0ddbb8fa7 100644 (file)
--- a/src/gram.h
+++ b/src/gram.h
@@ -1,5 +1,6 @@
 /* Data definitions for internal representation of bison's input,
 /* Data definitions for internal representation of bison's input,

-   Copyright 1984, 1986, 1989, 1992, 2001  Free Software Foundation, Inc.
+   Copyright (C) 1984, 1986, 1989, 1992, 2001, 2002
+   Free Software Foundation, Inc.

 
    This file is part of Bison, the GNU Compiler Compiler.
 
 
    This file is part of Bison, the GNU Compiler Compiler.
 


@@ -21,45 +22,62 @@
 #ifndef GRAM_H_
 # define GRAM_H_
 
 #ifndef GRAM_H_
 # define GRAM_H_
 

-/* representation of the grammar rules:
+/* Representation of the grammar rules:

 
 

-   ntokens is the number of tokens, and nvars is the number of
-   variables (nonterminals).  nsyms is the total number, ntokens +
+   NTOKENS is the number of tokens, and NVARS is the number of
+   variables (nonterminals).  NSYMS is the total number, ntokens +

    nvars.
 
    nvars.
 

-   (the true number of token values assigned is ntokens reduced by one
-   for each alias declaration)
-

    Each symbol (either token or variable) receives a symbol number.
    Each symbol (either token or variable) receives a symbol number.

-   Numbers 0 to ntokens-1 are for tokens, and ntokens to nsyms-1 are
-   for variables.  Symbol number zero is the end-of-input token.  This
-   token is counted in ntokens.
-
-   The rules receive rule numbers 1 to nrules in the order they are
-   written.  Actions and guards are accessed via the rule number.
+   Numbers 0 to NTOKENS - 1 are for tokens, and NTOKENS to NSYMS - 1
+   are for variables.  Symbol number zero is the end-of-input token.
+   This token is counted in ntokens.  The true number of token values
+   assigned is NTOKENS reduced by one for each alias declaration.
+
+   The rules receive rule numbers 1 to NRULES in the order they are
+   written.  More precisely Bison augments the grammar with the
+   initial rule, `$accept: START-SYMBOL $end', which is numbered 1,
+   all the user rules are 2, 3 etc.  Each time a rule number is
+   presented to the user, we subtract 1, so *displayed* rule numbers
+   are 0, 1, 2...
+
+   Internally, we cannot use the number 0 for a rule because for
+   instance RITEM stores both symbol (the RHS) and rule numbers: the
+   symbols are shorts >= 0, and rule number are stored negative.
+   Therefore 0 cannot be used, since it would be both the rule number
+   0, and the token $end).
+
+   Actions are accessed via the rule number.

 
    The rules themselves are described by several arrays: amongst which
 
    The rules themselves are described by several arrays: amongst which

-   RITEM, and RULE_TABLE.
+   RITEM, and RULES.
+
+   RULES is an array of struct rule_s, which members are:

 
 

-   RULE_TABLE is an array of struct rule_s, which members are:
+   RULES[R].lhs -- the symbol of the left hand side of rule R.

 
 

-   RULE_TABLE[R].lhs -- the symbol number of the left hand side of
-   rule R.  If -1, the rule has been thrown out by reduce.c and should
-   be ignored.
+   RULES[R].rhs -- the index in RITEM of the beginning of the portion
+   for rule R.

 
 

-   RULE_TABLE[R].rhs -- the index in RITEM of the beginning of the
-   portion for rule R.
+   RULES[R].prec -- the symbol providing the precedence level of R.

 
 

-   RULE_TABLE[R].prec -- the precedence level of R.
+   RULES[R].precsym -- the symbol attached (via %prec) to give its
+   precedence to R.  Of course, if set, it is equal to `prec', but we
+   need to distinguish one from the other when reducing: a symbol used
+   in a %prec is not useless.

 
 

-   RULE_TABLE[R].precsym -- the symbol-number of the symbol in %prec
-   for R (if any).
+   RULES[R].assoc -- the associativity of R.

 
 

-   RULE_TABLE[R].assoc -- the associativity of R.
+   RULES[R].dprec -- the dynamic precedence level of R (for GLR
+   parsing).

 
 

-   RULE_TABLE[R].line -- the line where R was defined.
+   RULES[R].merger -- index of merging function for R (for GLR
+   parsing).

 
 

-   RULE_TABLE[R].useful -- TRUE iff the rule is used.
+   RULES[R].line -- the line where R was defined.
+
+   RULES[R].useful -- TRUE iff the rule is used (i.e., FALSE if thrown
+   away by reduce).

 
    The right hand side is stored as symbol numbers in a portion of
    RITEM.
 
    The right hand side is stored as symbol numbers in a portion of
    RITEM.


@@ -69,96 +87,170 @@
    contains minus R, which identifies it as the end of a portion and
    says which rule it is for.
 
    contains minus R, which identifies it as the end of a portion and
    says which rule it is for.
 

-   The portions of RITEM come in order of increasing rule number and
-   are followed by an element which is zero to mark the end.  nitems
-   is the total length of ritem, not counting the final zero.  Each
-   element of ritem is called an "item" and its index in ritem is an
-   item number.
+   The portions of RITEM come in order of increasing rule number.
+   NRITEMS is the total length of RITEM.  Each element of RITEM is
+   called an "item" and its index in RITEM is an item number.

 
    Item numbers are used in the finite state machine to represent
    places that parsing can get to.
 
 
    Item numbers are used in the finite state machine to represent
    places that parsing can get to.
 

-   SPREC records the precedence level of each symbol.
+   SYMBOLS[I]->prec records the precedence level of each symbol.

 
    Precedence levels are assigned in increasing order starting with 1
    so that numerically higher precedence values mean tighter binding
    as they ought to.  Zero as a symbol or rule's precedence means none
    is assigned.
 
 
    Precedence levels are assigned in increasing order starting with 1
    so that numerically higher precedence values mean tighter binding
    as they ought to.  Zero as a symbol or rule's precedence means none
    is assigned.
 

-   Associativities are recorded similarly in rassoc and sassoc.  */
+   Associativities are recorded similarly in SYMBOLS[I]->assoc.  */

 
 

+# include "location.h"
+# include "symtab.h"

 
 

-#define        ISTOKEN(s)      ((s) < ntokens)
-#define        ISVAR(s)        ((s) >= ntokens)
+# define ISTOKEN(s)    ((s) < ntokens)
+# define ISVAR(s)      ((s) >= ntokens)

 
 

-extern int nitems;
-extern int nrules;

 extern int nsyms;
 extern int ntokens;
 extern int nvars;
 
 extern int nsyms;
 extern int ntokens;
 extern int nvars;
 

-extern short *ritem;
+typedef int item_number_t;
+# define ITEM_NUMBER_MAX ((item_number_t) INT_MAX)
+# define ITEM_NUMBER_MIN ((item_number_t) MIN_MAX)
+extern item_number_t *ritem;
+extern unsigned int nritems;

 
 

-extern short *sprec;
-extern short *sassoc;
+/* There is weird relationship between OT1H item_number_t and OTOH
+   symbol_number_t and rule_number_t: we store the latter in
+   item_number_t.  symbol_number_t are stored as are, while
+   the negation of (rule_number_t + 1) are stored.

 
 

-extern int start_symbol;
+   Therefore, an symbol_number_t must be a valid item_number_t, and we
+   sometimes have to perform the converse transformation.  */
+# define symbol_number_as_item_number(Tok) ((item_number_t) (Tok))
+# define item_number_as_symbol_number(Ite) ((symbol_number_t) (Ite))

 
 

-/* associativity values in elements of rassoc, sassoc.  */
-typedef enum
-{
-  right_assoc,
-  left_assoc,
-  non_assoc
-} associativity;
+extern symbol_number_t start_symbol;

 
 

+/* Rules numbers. */
+typedef short rule_number_t;
+# define RULE_NUMBER_MAX ((rule_number_t) SHRT_MAX)
+extern rule_number_t nrules;
+# define int_of_rule_number(RNum) ((int) (RNum))
+# define rule_number_as_item_number(RNum) ((item_number_t) (- RNum - 1))
+# define item_number_as_rule_number(INum) ((rule_number_t) (- INum - 1))
+
+
+/*--------.
+| Rules.  |
+`--------*/

 
 typedef struct rule_s
 {
 
 typedef struct rule_s
 {

-  short lhs;
-  short rhs;
-  short prec;
-  short precsym;
-  short assoc;
-  short line;
+  /* The number of the rule in the source.  It is usually the index in
+     RULES too, except if there are useless rules.  */
+  rule_number_t user_number;
+
+  /* The index in RULES.  Usually the rule number in the source,
+     except if some rules are useless.  */
+  rule_number_t number;
+
+  symbol_t *lhs;
+  item_number_t *rhs;
+
+  /* This symbol provides both the associativity, and the precedence. */
+  symbol_t *prec;
+
+  short dprec;
+  short merger;
+
+  /* This symbol was attached to the rule via %prec. */
+  symbol_t *precsym;
+
+  location_t location;

   bool useful;
 
   const char *action;
   bool useful;
 
   const char *action;

-  short action_line;
-
-  const char *guard;
-  short guard_line;
+  location_t action_location;

 } rule_t;
 
 } rule_t;
 

-extern struct rule_s *rule_table;
+extern struct rule_s *rules;
+
+/* A function that selects a rule.  */
+typedef bool (*rule_filter_t) PARAMS ((rule_t *r));
+
+/* Return true IFF the rule has a `number' smaller than NRULES.  */
+bool rule_useful_p PARAMS ((rule_t *r));
+
+/* Return true IFF the rule has a `number' higher than NRULES.  */
+bool rule_useless_p PARAMS ((rule_t *r));
+
+/* Return true IFF the rule is not flagged as useful *and* is useful.
+   In other words, it was discarded because of conflicts.  */
+bool rule_never_reduced_p PARAMS ((rule_t *r));

 
 

-/* token translation table: indexed by a token number as returned by
-   the user's yylex routine, it yields the internal token number used
-   by the parser and throughout bison.  */
+/* Print this RULE's number and lhs on OUT.  If a PREVIOUS_LHS was
+   already displayed (by a previous call for another rule), avoid
+   useless repetitions.  */
+void rule_lhs_print PARAMS ((rule_t *rule, symbol_t *previous_lhs, FILE *out));

 
 

-extern short *token_translations;
+/* Return the length of the RHS.  */
+int rule_rhs_length PARAMS ((rule_t *rule));
+
+/* Print this RULE's RHS on OUT.  */
+void rule_rhs_print PARAMS ((rule_t *rule, FILE *out));
+
+/* Print this RULE on OUT.  */
+void rule_print PARAMS ((rule_t *rule, FILE *out));
+
+
+
+
+/* Table of the symbols, indexed by the symbol number. */
+extern symbol_t **symbols;
+
+/* TOKEN_TRANSLATION -- a table indexed by a token number as returned
+   by the user's yylex routine, it yields the internal token number
+   used by the parser and throughout bison.  */
+extern symbol_number_t *token_translations;

 extern int max_user_token_number;
 
 extern int max_user_token_number;
 

-/* SEMANTIC_PARSER is nonzero if the input file says to use the hairy
-   parser that provides for semantic error recovery.  If it is zero,
-   the yacc-compatible simplified parser is used.  */

 
 

-extern int semantic_parser;
+
+/* GLR_PARSER is nonzero if the input file says to use the GLR
+   (Generalized LR) parser, and to output some additional
+   information used by the GLR algorithm. */
+
+extern int glr_parser;

 
 /* PURE_PARSER is nonzero if should generate a parser that is all pure
    and reentrant.  */
 
 extern int pure_parser;
 
 
 /* PURE_PARSER is nonzero if should generate a parser that is all pure
    and reentrant.  */
 
 extern int pure_parser;
 

-/* ERROR_TOKEN_NUMBER is the token number of the error token.  */
-
-extern int error_token_number;
-
-

 /* Dump RITEM for traces. */
 void ritem_print PARAMS ((FILE *out));
 
 /* Return the size of the longest rule RHS.  */
 size_t ritem_longest_rhs PARAMS ((void));
 
 /* Dump RITEM for traces. */
 void ritem_print PARAMS ((FILE *out));
 
 /* Return the size of the longest rule RHS.  */
 size_t ritem_longest_rhs PARAMS ((void));
 

+/* Print the grammar's rules numbers from BEGIN (inclusive) to END
+   (exclusive) on OUT under TITLE.  */
+void grammar_rules_partial_print PARAMS ((FILE *out, const char *title,
+                                         rule_filter_t filter));
+
+/* Print the grammar's rules on OUT.  */
+void grammar_rules_print PARAMS ((FILE *out));
+
+/* Dump the grammar. */
+void grammar_dump PARAMS ((FILE *out, const char *title));
+
+/* Report on STDERR the rules that are not flagged USEFUL, using the
+   MESSAGE (which can be `useless rule' when invoked after grammar
+   reduction, or `never reduced' after conflicts were taken into
+   account).  */
+void grammar_rules_never_reduced_report PARAMS ((const char *message));
+
+/* Free the packed grammar. */
+void grammar_free PARAMS ((void));
+

 #endif /* !GRAM_H_ */
 #endif /* !GRAM_H_ */