Encapsulate code properties and related functionality for the various

destructors, printers, and actions into a code_props structure and
interface.  This patch merely implements code_props in scan-code.h and
scan-code.l.  Future patches will rewrite other modules to use it.
Discussed starting at
<http://lists.gnu.org/archive/html/bison-patches/2006-11/msg00020.html>.
* src/location.h (EMPTY_LOCATION_INIT): Define so that it's easier to
consistently initialize const structs that have an empty location
field.
* src/location.c (empty_location): Initialize with EMPTY_LOCATION_INIT
to ensure consistency.
* src/scan-code.h (code_props): New structure.
(code_props_none_init, CODE_PROPS_NONE_INIT, code_props_none): New
function, macro, and const global variable for initializing a
code_props with no code.
(code_props_plain_init, code_props_symbol_action_init,
code_props_rule_action_init, code_props_translate_code): The rest of
the new code_props functional interface.  Among other things, the init
functions set the code_props kind field so that
code_props_translate_code will know whether to behave like
translate_symbol_action, translate_rule_action, or translate_code.
These old translate functions must remain until all other modules are
updated to use the new code_props interface.
(code_scanner_last_string_free): New function similar to
gram_scanner_last_string_free.
(code_scanner_free): Add documentation.
* src/scan-code.l: Implement the new interface.
(code_lex): Make it static, add a code_props* argument, and remove the
rule argument.
(last_string): New static global similar to the one in scan-gram.l.
(SC_RULE_ACTION): Update to use the code_props* argument to code_lex
instead of rule.
(SC_SYMBOL_ACTION): For $$, set the is_value_used member of the
code_props since Bison may one day use this information for destructors
and printers.
(<*><<EOF>>): Use STRING_FINISH so that last_string is set.
(handle_action_dollar): Use symbol_list_n_get and set used flag
directly since symbol_list_n_used_set is removed.
(translate_action): Add a code_props* argument and remove the rule,
action, and location arguments.  Pass the code_props* on to code_lex.
(translate_rule_action, translate_symbol_action, translate_code):
Rewrite as wrappers around the new code_props interface.
* src/symlist.h, src/symlist.c (symbol_list_n_used_set): Remove since
it would eventually need to break the encapsulation of code_props.

ChangeLog

@@ -1,3 +1,50 @@
+2007-01-02  Joel E. Denny  <jdenny@ces.clemson.edu>
+
+	Encapsulate code properties and related functionality for the various
+	destructors, printers, and actions into a code_props structure and
+	interface.  This patch merely implements code_props in scan-code.h and
+	scan-code.l.  Future patches will rewrite other modules to use it.
+	Discussed starting at
+	<http://lists.gnu.org/archive/html/bison-patches/2006-11/msg00020.html>.
+	* src/location.h (EMPTY_LOCATION_INIT): Define so that it's easier to
+	consistently initialize const structs that have an empty location
+	field.
+	* src/location.c (empty_location): Initialize with EMPTY_LOCATION_INIT
+	to ensure consistency.
+	* src/scan-code.h (code_props): New structure.
+	(code_props_none_init, CODE_PROPS_NONE_INIT, code_props_none): New
+	function, macro, and const global variable for initializing a
+	code_props with no code.
+	(code_props_plain_init, code_props_symbol_action_init,
+	code_props_rule_action_init, code_props_translate_code): The rest of
+	the new code_props functional interface.  Among other things, the init
+	functions set the code_props kind field so that
+	code_props_translate_code will know whether to behave like
+	translate_symbol_action, translate_rule_action, or translate_code.
+	These old translate functions must remain until all other modules are
+	updated to use the new code_props interface.
+	(code_scanner_last_string_free): New function similar to
+	gram_scanner_last_string_free.
+	(code_scanner_free): Add documentation.
+	* src/scan-code.l: Implement the new interface.
+	(code_lex): Make it static, add a code_props* argument, and remove the
+	rule argument.
+	(last_string): New static global similar to the one in scan-gram.l.
+	(SC_RULE_ACTION): Update to use the code_props* argument to code_lex
+	instead of rule.
+	(SC_SYMBOL_ACTION): For $$, set the is_value_used member of the
+	code_props since Bison may one day use this information for destructors
+	and printers.
+	(<*><<EOF>>): Use STRING_FINISH so that last_string is set.
+	(handle_action_dollar): Use symbol_list_n_get and set used flag
+	directly since symbol_list_n_used_set is removed.
+	(translate_action): Add a code_props* argument and remove the rule,
+	action, and location arguments.  Pass the code_props* on to code_lex.
+	(translate_rule_action, translate_symbol_action, translate_code):
+	Rewrite as wrappers around the new code_props interface.
+	* src/symlist.h, src/symlist.c (symbol_list_n_used_set): Remove since
+	it would eventually need to break the encapsulation of code_props.
+
 2007-01-01  Joel E. Denny  <jdenny@ces.clemson.edu>
 
 	* etc/.cvsignore: New.

src/location.c

@@ -1,5 +1,5 @@
 /* Locations for Bison
-   Copyright (C) 2002, 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2005, 2006, 2007 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -27,7 +27,7 @@
 #include "complain.h"
 #include "location.h"
 
-location const empty_location;
+location const empty_location = EMPTY_LOCATION_INIT;
 
 /* If BUF is null, add BUFSIZE (which in this case must be less than
    INT_MAX) to COLUMN; otherwise, add mbsnwidth (BUF, BUFSIZE, 0) to

src/location.h

@@ -1,5 +1,5 @@
 /* Locations for Bison
-   Copyright (C) 2002, 2004, 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -71,6 +71,7 @@ typedef struct
 
 #define YYLTYPE location
 
+#define EMPTY_LOCATION_INIT {{NULL, 0, 0}, {NULL, 0, 0}}
 extern location const empty_location;
 
 /* Set *LOC and adjust scanner cursor to account for token TOKEN of

src/scan-code.h

@@ -1,6 +1,6 @@
-/* Bison Action Scanner
+/* Bison code properties structure and scanner.
 
-   Copyright (C) 2006 Free Software Foundation, Inc.
+   Copyright (C) 2006, 2007 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -24,13 +24,149 @@
 # define SCAN_CODE_H_
 
 # include "location.h"
-# include "symlist.h"
 
-/* Keeps track of the maximum number of semantic values to the left of
+struct symbol_list;
-   a handle (those referenced by $0, $-1, etc.) are required by the
+
-   semantic actions of this grammar. */
+/**
+ * Keeps track of the maximum number of semantic values to the left of a handle
+ * (those referenced by $0, $-1, etc.) that are required by the semantic
+ * actions of this grammar.
+ */
 extern int max_left_semantic_context;
 
+/**
+ * A code passage captured from the grammar file and possibly translated,
+ * and/or properties associated with such a code passage.  Don't break
+ * encapsulation by modifying the fields directly.  Use the provided interface
+ * functions.
+ */
+typedef struct code_props {
+  /** Set by the init functions.  */
+  enum {
+    CODE_PROPS_NONE, CODE_PROPS_PLAIN,
+    CODE_PROPS_SYMBOL_ACTION, CODE_PROPS_RULE_ACTION
+  } kind;
+
+  /** \c NULL iff \c code_props::kind is \c CODE_PROPS_NONE.  */
+  char const *code;
+  /** Undefined iff \c code_props::code is \c NULL.  */
+  location location;
+
+  /**
+   * \c false iff either:
+   *   - \c code_props_translate_code has never previously been invoked for
+   *     the \c code_props that would contain the code passage associated
+   *     with \c self.  (That \c code_props is not the same as this one if this
+   *     one is for a RHS \c symbol_list node.  Instead, it's the \c code_props
+   *     for the LHS symbol of the same rule.)
+   *   - \c code_props_translate_code has been invoked for that \c code_props,
+   *     but the symbol value associated with this \c code_props was not
+   *     referenced in the code passage.
+   */
+  bool is_value_used;
+
+  /** \c NULL iff \c code_props::kind is not \c CODE_PROPS_RULE_ACTION.  */
+  struct symbol_list *rule;
+} code_props;
+
+/**
+ * \pre
+ *   - <tt>self != NULL</tt>.
+ * \post
+ *   - \c self has been overwritten to contain no code.
+ */
+void code_props_none_init (code_props *self);
+
+/** Equivalent to \c code_props_none_init.  */
+#define CODE_PROPS_NONE_INIT \
+  {CODE_PROPS_NONE, NULL, EMPTY_LOCATION_INIT, false, NULL}
+
+/** Initialized by \c CODE_PROPS_NONE_INIT with no further modification.  */
+extern code_props const code_props_none;
+
+/**
+ * \pre
+ *   - <tt>self != NULL</tt>.
+ *   - <tt>code != NULL</tt>.
+ *   - \c code is an untranslated code passage containing no Bison escapes.
+ *   - \c code was extracted from the grammar file at \c code_loc.
+ * \post
+ *   - \c self has been overwritten to represent the specified plain code
+ *     passage.
+ *   - \c self will become invalid if the caller frees \c code before invoking
+ *     \c code_props_translate_code on \c self.
+ */
+void code_props_plain_init (code_props *self, char const *code,
+                            location code_loc);
+
+/**
+ * \pre
+ *   - <tt>self != NULL</tt>.
+ *   - <tt>code != NULL</tt>.
+ *   - \c code is an untranslated code passage.  The only Bison escapes it
+ *     might contain are $$ and \@$, referring to a single symbol.
+ *   - \c code was extracted from the grammar file at \c code_loc.
+ * \post
+ *   - \c self has been overwritten to represent the specified symbol action.
+ *   - \c self will become invalid if the caller frees \c code before invoking
+ *     \c code_props_translate_code on \c self.
+ */
+void code_props_symbol_action_init (code_props *self, char const *code,
+                                    location code_loc);
+
+/**
+ * \pre
+ *   - <tt>self != NULL</tt>.
+ *   - <tt>code != NULL</tt>.
+ *   - <tt>rule != NULL</tt>.
+ *   - \c code is the untranslated action of the rule for which \c rule is the
+ *     LHS node.  Thus, \c code possibly contains Bison escapes such as $$, $1,
+ *     $2, etc referring to the values of the rule.
+ *   - \c code was extracted from the grammar file at \c code_loc.
+ * \post
+ *   - \c self has been overwritten to represent the specified rule action.
+ *   - \c self does not claim responsibility for the memory of \c rule.
+ *   - \c self will become invalid if:
+ *     - The caller frees \c code before invoking \c code_props_translate_code
+ *       on \c self.
+ *     - The caller frees \c rule.
+ */
+void code_props_rule_action_init (code_props *self, char const *code,
+                                  location code_loc, struct symbol_list *rule);
+
+/**
+ * \pre
+ *   - If there's a code passage contained in \c self and it contains Bison
+ *     escapes, all grammar declarations have already been parsed as they may
+ *     affect warnings and complaints issued here.
+ * \post
+ *   - All M4-special symbols and Bison escapes have been translated in
+ *     \c self->code.
+ *   - <tt>self->code != self->code\@pre</tt> unless
+ *     <tt>self->code\@pre = NULL</tt>.
+ */
+void code_props_translate_code (code_props *self);
+
+/**
+ * \pre
+ *   - None.
+ * \post
+ *   - The dynamic memory allocated by the previous invocation of
+ *     \c code_props_translate_code (if any) was freed.  The \c code_props
+ *     instance for which \c code_props_translate_code was invoked is now
+ *     invalid.
+ */
+void code_scanner_last_string_free (void);
+
+/**
+ * \pre
+ *   - None.
+ * \post
+ *   - All dynamic memory allocated during any previous invocations of
+ *     \c code_props_translate_code, \c translate_rule_action,
+ *     \c translate_symbol_action, and \c translate_code has been freed.  All
+ *     \c code_props instances may now be invalid.
+ */
 void code_scanner_free (void);
 
 /* The action of the rule R contains $$, $1 etc. referring to the values

src/scan-code.l

@@ -1,6 +1,6 @@
 /* Bison Action Scanner                             -*- C -*-
 
-   Copyright (C) 2006 Free Software Foundation, Inc.
+   Copyright (C) 2006, 2007 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -39,10 +39,11 @@
 #include <quote.h>
 
 #include "scan-code.h"
+#include "symlist.h"
 
 /* The current calling start condition: SC_RULE_ACTION or
    SC_SYMBOL_ACTION. */
-# define YY_DECL char *code_lex (int sc_context, symbol_list *rule)
+# define YY_DECL static char *code_lex (code_props *self, int sc_context)
 YY_DECL;
 
 #define YY_USER_ACTION  location_compute (loc, &loc->end, yytext, yyleng);
@@ -53,6 +54,9 @@ static void handle_action_at (symbol_list *rule, char *cp, location at_loc);
 static location the_location;
 static location *loc = &the_location;
 
+/* A string representing the most recent translation.  */
+static char *last_string;
+
 /* True if an untyped $$ or $n was seen.  */
 static bool untyped_var_seen;
 %}
@@ -151,8 +155,12 @@ splice	 (\\[ \f\t\v]*\n)*
 
 <SC_RULE_ACTION>
 {
-  "$"("<"{tag}">")?(-?[0-9]+|"$")   handle_action_dollar (rule, yytext, *loc);
+  "$"("<"{tag}">")?(-?[0-9]+|"$")  {
-  "@"(-?[0-9]+|"$")		    handle_action_at (rule, yytext, *loc);
+    handle_action_dollar (self->rule, yytext, *loc);
+  }
+  "@"(-?[0-9]+|"$") {
+    handle_action_at (self->rule, yytext, *loc);
+  }
 
   "$"  {
     warn_at (*loc, _("stray `$'"));
@@ -190,7 +198,10 @@ splice	 (\\[ \f\t\v]*\n)*
 
 <SC_SYMBOL_ACTION>
 {
-  "$$"   obstack_sgrow (&obstack_for_string, "]b4_dollar_dollar[");
+  "$$" {
+    obstack_sgrow (&obstack_for_string, "]b4_dollar_dollar[");
+    self->is_value_used = true;
+  }
   "@$"   obstack_sgrow (&obstack_for_string, "]b4_at_dollar[");
 }
 
@@ -215,8 +226,8 @@ splice	 (\\[ \f\t\v]*\n)*
 
  /* End of processing. */
 <*><<EOF>>	 {
-                   obstack_1grow (&obstack_for_string, '\0');
+                   STRING_FINISH;
-		   return obstack_finish (&obstack_for_string);
+                   return last_string;
                  }
 
 %%
@@ -238,7 +249,7 @@ int max_left_semantic_context = 0;
 static void
 handle_action_dollar (symbol_list *rule, char *text, location dollar_loc)
 {
-  const char *type_name = NULL;
+  char const *type_name = NULL;
   char *cp = text + 1;
   symbol_list *effective_rule;
   int effective_rule_length;
@@ -321,7 +332,8 @@ handle_action_dollar (symbol_list *rule, char *text, location dollar_loc)
 	  obstack_fgrow3 (&obstack_for_string,
 			  "]b4_rhs_value(%d, %d, [%s])[",
 			  effective_rule_length, n, type_name);
-	  symbol_list_n_used_set (effective_rule, n, true);
+          if (n > 0)
+            symbol_list_n_get (effective_rule, n)->used = true;
 	}
       else
 	complain_at (dollar_loc, _("integer out of range: %s"), quote (text));
@@ -368,12 +380,11 @@ handle_action_at (symbol_list *rule, char *text, location at_loc)
 | Initialize the scanner.  |
 `-------------------------*/
 
-/* Translate the dollars and ats in \a a, whose location is \a l.  The
+/* Translate the dollars and ats in \a self, in the context \a sc_context
-   translation is for \a rule, in the context \a sc_context
    (SC_RULE_ACTION, SC_SYMBOL_ACTION, INITIAL).  */
 
 static char const *
-translate_action (int sc_context, symbol_list *rule, char const *a, location l)
+translate_action (code_props *self, int sc_context)
 {
   char *res;
   static bool initialized = false;
@@ -384,36 +395,82 @@ translate_action (int sc_context, symbol_list *rule, char const *a, location l)
       initialized = true;
     }
 
-  loc->start = loc->end = l.start;
+  loc->start = loc->end = self->location.start;
-  yy_switch_to_buffer (yy_scan_string (a));
+  yy_switch_to_buffer (yy_scan_string (self->code));
-  res = code_lex (sc_context, rule);
+  res = code_lex (self, sc_context);
   yy_delete_buffer (YY_CURRENT_BUFFER);
 
   return res;
 }
 
-char const *
+/*------------------------------------------------------------------------.
-translate_rule_action (symbol_list *rule)
+| Implementation of the public interface as documented in "scan-code.h".  |
+`------------------------------------------------------------------------*/
+
+void
+code_props_none_init (code_props *self)
 {
-  return translate_action (SC_RULE_ACTION, rule, rule->action,
+  *self = code_props_none;
-			   rule->action_location);
 }
 
-char const *
+code_props const code_props_none = CODE_PROPS_NONE_INIT;
-translate_symbol_action (char const *a, location l)
+
+void
+code_props_plain_init (code_props *self, char const *code, location code_loc)
 {
-  return translate_action (SC_SYMBOL_ACTION, NULL, a, l);
+  self->kind = CODE_PROPS_PLAIN;
+  self->code = code;
+  self->location = code_loc;
+  self->is_value_used = false;
+  self->rule = NULL;
 }
 
-char const *
+void
-translate_code (char const *a, location l)
+code_props_symbol_action_init (code_props *self, char const *code,
+                               location code_loc)
 {
-  return translate_action (INITIAL, NULL, a, l);
+  self->kind = CODE_PROPS_SYMBOL_ACTION;
+  self->code = code;
+  self->location = code_loc;
+  self->is_value_used = false;
+  self->rule = NULL;
 }
 
-/*-----------------------------------------------.
+void
-| Free all the memory allocated to the scanner.  |
+code_props_rule_action_init (code_props *self, char const *code,
-`-----------------------------------------------*/
+                             location code_loc, symbol_list *rule)
+{
+  self->kind = CODE_PROPS_RULE_ACTION;
+  self->code = code;
+  self->location = code_loc;
+  self->is_value_used = false;
+  self->rule = rule;
+}
+
+void
+code_props_translate_code (code_props *self)
+{
+  switch (self->kind)
+    {
+      case CODE_PROPS_NONE:
+        break;
+      case CODE_PROPS_PLAIN:
+        self->code = translate_action (self, INITIAL);
+        break;
+      case CODE_PROPS_SYMBOL_ACTION:
+        self->code = translate_action (self, SC_SYMBOL_ACTION);
+        break;
+      case CODE_PROPS_RULE_ACTION:
+        self->code = translate_action (self, SC_RULE_ACTION);
+        break;
+    }
+}
+
+void
+code_scanner_last_string_free (void)
+{
+  STRING_FREE;
+}
 
 void
 code_scanner_free (void)
@@ -422,3 +479,30 @@ code_scanner_free (void)
   /* Reclaim Flex's buffers.  */
   yylex_destroy ();
 }
+
+char const *
+translate_rule_action (symbol_list *rule)
+{
+  code_props cp;
+  code_props_rule_action_init (&cp, rule->action, rule->action_location, rule);
+  code_props_translate_code (&cp);
+  return cp.code;
+}
+
+char const *
+translate_symbol_action (char const *a, location l)
+{
+  code_props cp;
+  code_props_symbol_action_init (&cp, a, l);
+  code_props_translate_code (&cp);
+  return cp.code;
+}
+
+char const *
+translate_code (char const *a, location l)
+{
+  code_props cp;
+  code_props_plain_init (&cp, a, l);
+  code_props_translate_code (&cp);
+  return cp.code;
+}

src/symlist.c

@@ -1,6 +1,6 @@
 /* Lists of symbols for Bison
 
-   Copyright (C) 2002, 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2005, 2006, 2007 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -207,18 +207,6 @@ symbol_list_n_type_name_get (symbol_list *l, location loc, int n)
 }
 
 
-/*--------------------------------------.
-| The item N in symbol list L is USED.  |
-`--------------------------------------*/
-
-void
-symbol_list_n_used_set (symbol_list *l, int n, bool used)
-{
-  l = symbol_list_n_get (l, n);
-  if (l)
-    l->used = used;
-}
-
 void
 symbol_list_destructor_set (symbol_list *node, const char *destructor,
                             location loc)

src/symlist.h

@@ -1,6 +1,6 @@
 /* Lists of symbols for Bison
 
-   Copyright (C) 2002, 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2005, 2006, 2007 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -106,9 +106,6 @@ symbol_list *symbol_list_n_get (symbol_list *l, int n);
    symbol N in rule RULE.  */
 uniqstr symbol_list_n_type_name_get (symbol_list *l, location loc, int n);
 
-/** The item \c n in symbol list \c l is \c used.  */
-void symbol_list_n_used_set (symbol_list *l, int n, bool used);
-
 /** Set the \c \%destructor for \c node as \c destructor at \c loc.  */
 void symbol_list_destructor_set (symbol_list *node, const char *destructor,
                                  location loc);