Use unique_xmalloc_ptr in apply_ext_lang_type_printers

This changes apply_ext_lang_type_printers to use unique_xmalloc_ptr,
removing some manual memory management.  Regression tested on x86-64
Fedora 36.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

gdb/extension-priv.h

@@ -137,7 +137,7 @@ struct extension_language_ops
 			       struct ext_lang_type_printers *);
 
   /* Try to pretty-print TYPE.  If successful the pretty-printed type is
-     stored in *PRETTIED_TYPE, and the caller must free it.
+     stored in *PRETTIED_TYPE.
      Returns EXT_LANG_RC_OK upon success, EXT_LANG_RC_NOP if the type
      is not recognized, and EXT_LANG_RC_ERROR if an error was encountered.
      This function has a bit of a funny name, since it actually applies
@@ -146,7 +146,8 @@ struct extension_language_ops
   enum ext_lang_rc (*apply_type_printers)
     (const struct extension_language_defn *,
      const struct ext_lang_type_printers *,
-     struct type *, char **prettied_type);
+     struct type *,
+     gdb::unique_xmalloc_ptr<char> *prettied_type);
 
   /* Called after a type has been printed to give the type pretty-printer
      mechanism an opportunity to clean up.  */

gdb/extension.c

@@ -418,13 +418,13 @@ ext_lang_type_printers::ext_lang_type_printers ()
    returning the result of the first one that succeeds.
    If there was an error, or if no printer succeeds, then NULL is returned.  */
 
-char *
+gdb::unique_xmalloc_ptr<char>
 apply_ext_lang_type_printers (struct ext_lang_type_printers *printers,
 			      struct type *type)
 {
   for (const struct extension_language_defn *extlang : extension_languages)
     {
-      char *result = NULL;
+      gdb::unique_xmalloc_ptr<char> result;
       enum ext_lang_rc rc;
 
       if (extlang->ops == nullptr
@@ -435,7 +435,7 @@ apply_ext_lang_type_printers (struct ext_lang_type_printers *printers,
       switch (rc)
 	{
 	case EXT_LANG_RC_OK:
-	  gdb_assert (result != NULL);
+	  gdb_assert (result != nullptr);
 	  return result;
 	case EXT_LANG_RC_ERROR:
 	  return NULL;

gdb/extension.h

@@ -282,8 +282,8 @@ extern void eval_ext_lang_from_control_command (struct command_line *cmd);
 
 extern void auto_load_ext_lang_scripts_for_objfile (struct objfile *);
 
-extern char *apply_ext_lang_type_printers (struct ext_lang_type_printers *,
-					   struct type *);
+extern gdb::unique_xmalloc_ptr<char> apply_ext_lang_type_printers
+     (struct ext_lang_type_printers *, struct type *);
 
 extern int apply_ext_lang_val_pretty_printer
   (struct value *value, struct ui_file *stream, int recurse,

gdb/python/python.c

@@ -112,7 +112,8 @@ static void gdbpy_start_type_printers (const struct extension_language_defn *,
 				       struct ext_lang_type_printers *);
 static enum ext_lang_rc gdbpy_apply_type_printers
   (const struct extension_language_defn *,
-   const struct ext_lang_type_printers *, struct type *, char **);
+   const struct ext_lang_type_printers *, struct type *,
+   gdb::unique_xmalloc_ptr<char> *);
 static void gdbpy_free_type_printers (const struct extension_language_defn *,
 				      struct ext_lang_type_printers *);
 static void gdbpy_set_quit_flag (const struct extension_language_defn *);
@@ -1700,7 +1701,7 @@ gdbpy_start_type_printers (const struct extension_language_defn *extlang,
 
 /* If TYPE is recognized by some type printer, store in *PRETTIED_TYPE
    a newly allocated string holding the type's replacement name, and return
-   EXT_LANG_RC_OK.  The caller is responsible for freeing the string.
+   EXT_LANG_RC_OK.
    If there's a Python error return EXT_LANG_RC_ERROR.
    Otherwise, return EXT_LANG_RC_NOP.
    This is the extension_language_ops.apply_type_printers "method".  */
@@ -1708,7 +1709,8 @@ gdbpy_start_type_printers (const struct extension_language_defn *extlang,
 static enum ext_lang_rc
 gdbpy_apply_type_printers (const struct extension_language_defn *extlang,
 			   const struct ext_lang_type_printers *ext_printers,
-			   struct type *type, char **prettied_type)
+			   struct type *type,
+			   gdb::unique_xmalloc_ptr<char> *prettied_type)
 {
   PyObject *printers_obj = (PyObject *) ext_printers->py_type_printers;
   gdb::unique_xmalloc_ptr<char> result;
@@ -1763,7 +1765,7 @@ gdbpy_apply_type_printers (const struct extension_language_defn *extlang,
       return EXT_LANG_RC_ERROR;
     }
 
-  *prettied_type = result.release ();
+  *prettied_type = std::move (result);
   return EXT_LANG_RC_OK;
 }
 

gdb/typeprint.c

@@ -309,7 +309,6 @@ const char *
 typedef_hash_table::find_global_typedef (const struct type_print_options *flags,
 					 struct type *t)
 {
-  char *applied;
   void **slot;
   struct decl_field tf, *new_tf;
 
@@ -334,14 +333,12 @@ typedef_hash_table::find_global_typedef (const struct type_print_options *flags,
 
   *slot = new_tf;
 
-  applied = apply_ext_lang_type_printers (flags->global_printers, t);
+  gdb::unique_xmalloc_ptr<char> applied
+    = apply_ext_lang_type_printers (flags->global_printers, t);
 
-  if (applied != NULL)
-    {
-      new_tf->name = obstack_strdup (&flags->global_typedefs->m_storage,
-				     applied);
-      xfree (applied);
-    }
+  if (applied != nullptr)
+    new_tf->name = obstack_strdup (&flags->global_typedefs->m_storage,
+				   applied.get ());
 
   return new_tf->name;
 }