Remove a cleanup from parse_expression_for_completion

This removes a cleanup from parse_expression_for_completion, by
changing various expression-completion functions to use
gdb::unique_xmalloc_ptry rather than explicit malloc+free.

Regression tested by the buildbot.

gdb/ChangeLog
2018-02-21  Tom Tromey  <tom@tromey.com>

	* value.h: (extract_field_op): Update.
	* eval.c (extract_field_op): Return a const char *.
	* expression.h (parse_expression_for_completion): Update.
	* completer.c (complete_expression): Update.
	(add_struct_fields): Make fieldname const.
	* parse.c (expout_completion_name): Now a unique_xmalloc_ptr.
	(mark_completion_tag, parse_exp_in_context_1): Update.
	(parse_expression_for_completion): Change "name" to
	unique_xmalloc_ptr*.

gdb/ChangeLog

@@ -1,3 +1,15 @@
+2018-02-21  Tom Tromey  <tom@tromey.com>
+
+	* value.h: (extract_field_op): Update.
+	* eval.c (extract_field_op): Return a const char *.
+	* expression.h (parse_expression_for_completion): Update.
+	* completer.c (complete_expression): Update.
+	(add_struct_fields): Make fieldname const.
+	* parse.c (expout_completion_name): Now a unique_xmalloc_ptr.
+	(mark_completion_tag, parse_exp_in_context_1): Update.
+	(parse_expression_for_completion): Change "name" to
+	unique_xmalloc_ptr*.
+
 2018-02-21  Tom Tromey  <tom@tromey.com>
 
 	* infcall.c (call_function_by_hand_dummy): Use std::vector.

gdb/completer.c

@@ -962,7 +962,7 @@ location_completer_handle_brkchars (struct cmd_list_element *ignore,
 
 static void
 add_struct_fields (struct type *type, completion_list &output,
-		   char *fieldname, int namelen)
+		   const char *fieldname, int namelen)
 {
   int i;
   int computed_type_name = 0;
@@ -1016,12 +1016,11 @@ complete_expression (completion_tracker &tracker,
 		     const char *text, const char *word)
 {
   struct type *type = NULL;
-  char *fieldname;
+  gdb::unique_xmalloc_ptr<char> fieldname;
   enum type_code code = TYPE_CODE_UNDEF;
 
   /* Perform a tentative parse of the expression, to see whether a
      field completion is required.  */
-  fieldname = NULL;
   TRY
     {
       type = parse_expression_for_completion (text, &fieldname, &code);
@@ -1032,7 +1031,7 @@ complete_expression (completion_tracker &tracker,
     }
   END_CATCH
 
-  if (fieldname && type)
+  if (fieldname != nullptr && type)
     {
       for (;;)
 	{
@@ -1045,25 +1044,20 @@ complete_expression (completion_tracker &tracker,
       if (TYPE_CODE (type) == TYPE_CODE_UNION
 	  || TYPE_CODE (type) == TYPE_CODE_STRUCT)
 	{
-	  int flen = strlen (fieldname);
 	  completion_list result;
 
-	  add_struct_fields (type, result, fieldname, flen);
-	  xfree (fieldname);
+	  add_struct_fields (type, result, fieldname.get (),
+			     strlen (fieldname.get ()));
 	  tracker.add_completions (std::move (result));
 	  return;
 	}
     }
-  else if (fieldname && code != TYPE_CODE_UNDEF)
+  else if (fieldname != nullptr && code != TYPE_CODE_UNDEF)
     {
-      struct cleanup *cleanup = make_cleanup (xfree, fieldname);
-
-      collect_symbol_completion_matches_type (tracker, fieldname, fieldname,
-					      code);
-      do_cleanups (cleanup);
+      collect_symbol_completion_matches_type (tracker, fieldname.get (),
+					      fieldname.get (), code);
       return;
     }
-  xfree (fieldname);
 
   complete_files_symbols (tracker, text, word);
 }

gdb/eval.c

@@ -272,7 +272,7 @@ fetch_subexp_value (struct expression *exp, int *pc, struct value **valp,
    subexpression of the left-hand-side of the dereference.  This is
    used when completing field names.  */
 
-char *
+const char *
 extract_field_op (struct expression *exp, int *subexp)
 {
   int tem;

gdb/expression.h

@@ -101,8 +101,8 @@ extern expression_up parse_expression (const char *);
 extern expression_up parse_expression_with_language (const char *string,
 						     enum language lang);
 
-extern struct type *parse_expression_for_completion (const char *, char **,
-						     enum type_code *);
+extern struct type *parse_expression_for_completion
+    (const char *, gdb::unique_xmalloc_ptr<char> *, enum type_code *);
 
 extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
 				  const struct block *, int);

gdb/parse.c

@@ -88,7 +88,7 @@ static int expout_last_struct = -1;
 static enum type_code expout_tag_completion_type = TYPE_CODE_UNDEF;
 
 /* The token for tagged type name completion.  */
-static char *expout_completion_name;
+static gdb::unique_xmalloc_ptr<char> expout_completion_name;
 
 
 static unsigned int expressiondebug = 0;
@@ -575,9 +575,7 @@ mark_completion_tag (enum type_code tag, const char *ptr, int length)
 	      || tag == TYPE_CODE_STRUCT
 	      || tag == TYPE_CODE_ENUM);
   expout_tag_completion_type = tag;
-  expout_completion_name = (char *) xmalloc (length + 1);
-  memcpy (expout_completion_name, ptr, length);
-  expout_completion_name[length] = '\0';
+  expout_completion_name.reset (xstrndup (ptr, length));
 }
 
 
@@ -1137,8 +1135,7 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
   type_stack.depth = 0;
   expout_last_struct = -1;
   expout_tag_completion_type = TYPE_CODE_UNDEF;
-  xfree (expout_completion_name);
-  expout_completion_name = NULL;
+  expout_completion_name.reset ();
 
   comma_terminates = comma;
 
@@ -1277,11 +1274,11 @@ parse_expression_with_language (const char *string, enum language lang)
    reference; furthermore, if the parsing ends in the field name,
    return the field name in *NAME.  If the parsing ends in the middle
    of a field reference, but the reference is somehow invalid, throw
-   an exception.  In all other cases, return NULL.  Returned non-NULL
-   *NAME must be freed by the caller.  */
+   an exception.  In all other cases, return NULL.  */
 
 struct type *
-parse_expression_for_completion (const char *string, char **name,
+parse_expression_for_completion (const char *string,
+				 gdb::unique_xmalloc_ptr<char> *name,
 				 enum type_code *code)
 {
   expression_up exp;
@@ -1306,23 +1303,24 @@ parse_expression_for_completion (const char *string, char **name,
   if (expout_tag_completion_type != TYPE_CODE_UNDEF)
     {
       *code = expout_tag_completion_type;
-      *name = expout_completion_name;
-      expout_completion_name = NULL;
+      *name = std::move (expout_completion_name);
       return NULL;
     }
 
   if (expout_last_struct == -1)
     return NULL;
 
-  *name = extract_field_op (exp.get (), &subexp);
-  if (!*name)
-    return NULL;
+  const char *fieldname = extract_field_op (exp.get (), &subexp);
+  if (fieldname == NULL)
+    {
+      name->reset ();
+      return NULL;
+    }
 
+  name->reset (xstrdup (fieldname));
   /* This might throw an exception.  If so, we want to let it
      propagate.  */
   val = evaluate_subexpression_type (exp.get (), subexp);
-  /* (*NAME) is a part of the EXP memory block freed below.  */
-  *name = xstrdup (*name);
 
   return value_type (val);
 }

gdb/value.h

@@ -889,7 +889,7 @@ extern void fetch_subexp_value (struct expression *exp, int *pc,
 				struct value **val_chain,
 				int preserve_errors);
 
-extern char *extract_field_op (struct expression *exp, int *subexp);
+extern const char *extract_field_op (struct expression *exp, int *subexp);
 
 extern struct value *evaluate_subexp_with_coercion (struct expression *,
 						    int *, enum noside);