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.

1 files changed, 142 insertions, 6 deletions

diff --git a/src/scan-code.h b/src/scan-code.h
index f2d79720..a6e1fc13 100644
--- a/src/scan-code.h
+++ b/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
-   a handle (those referenced by $0, $-1, etc.) are required by the
-   semantic actions of this grammar. */
+struct symbol_list;
+
+/**
+ * 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