dir: make clear_directory() free all relevant memory

The calling convention for the dir API is supposed to end with a call to
clear_directory() to free up no longer needed memory.  However,
clear_directory() didn't free dir->entries or dir->ignored.  I believe
this was an oversight, but a number of callers noticed memory leaks and
started free'ing these.  Unfortunately, they did so somewhat haphazardly
(sometimes freeing the entries in the arrays, and sometimes only
free'ing the arrays themselves).  This suggests the callers weren't
trying to make sure any possible memory used might be free'd, but just
the memory they noticed their usecase definitely had allocated.

Fix this mess by moving all the duplicated free'ing logic into
clear_directory().  End by resetting dir to a pristine state so it could
be reused if desired.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clean.c

@@ -1021,11 +1021,7 @@ int cmd_clean(int argc, const char **argv, const char *prefix)
 		string_list_append(&del_list, rel);
 	}
 
-	for (i = 0; i < dir.nr; i++)
-		free(dir.entries[i]);
-
-	for (i = 0; i < dir.ignored_nr; i++)
-		free(dir.ignored[i]);
+	clear_directory(&dir);
 
 	if (interactive && del_list.nr > 0)
 		interactive_main_loop();

builtin/stash.c

@@ -875,11 +875,8 @@ static int get_untracked_files(const struct pathspec *ps, int include_untracked,
 		strbuf_addstr(untracked_files, ent->name);
 		/* NUL-terminate: will be fed to update-index -z */
 		strbuf_addch(untracked_files, '\0');
-		free(ent);
 	}
 
-	free(dir.entries);
-	free(dir.ignored);
 	clear_directory(&dir);
 	return found;
 }

dir.c

@@ -3009,8 +3009,8 @@ int remove_path(const char *name)
 }
 
 /*
- * Frees memory within dir which was allocated for exclude lists and
- * the exclude_stack.  Does not free dir itself.
+ * Frees memory within dir which was allocated, and resets fields for further
+ * use.  Does not free dir itself.
  */
 void clear_directory(struct dir_struct *dir)
 {
@@ -3030,6 +3030,13 @@ void clear_directory(struct dir_struct *dir)
 		free(group->pl);
 	}
 
+	for (i = 0; i < dir->ignored_nr; i++)
+		free(dir->ignored[i]);
+	for (i = 0; i < dir->nr; i++)
+		free(dir->entries[i]);
+	free(dir->ignored);
+	free(dir->entries);
+
 	stk = dir->exclude_stack;
 	while (stk) {
 		struct exclude_stack *prev = stk->prev;
@@ -3037,6 +3044,8 @@ void clear_directory(struct dir_struct *dir)
 		stk = prev;
 	}
 	strbuf_release(&dir->basebuf);
+
+	memset(&dir, 0, sizeof(*dir));
 }
 
 struct ondisk_untracked_cache {

dir.h

@@ -36,7 +36,7 @@
  *
  * - Use `dir.entries[]`.
  *
- * - Call `clear_directory()` when none of the contained elements are no longer in use.
+ * - Call `clear_directory()` when the contained elements are no longer in use.
  *
  */
 

wt-status.c

@@ -724,18 +724,14 @@ static void wt_status_collect_untracked(struct wt_status *s)
 		struct dir_entry *ent = dir.entries[i];
 		if (index_name_is_other(istate, ent->name, ent->len))
 			string_list_insert(&s->untracked, ent->name);
-		free(ent);
 	}
 
 	for (i = 0; i < dir.ignored_nr; i++) {
 		struct dir_entry *ent = dir.ignored[i];
 		if (index_name_is_other(istate, ent->name, ent->len))
 			string_list_insert(&s->ignored, ent->name);
-		free(ent);
 	}
 
-	free(dir.entries);
-	free(dir.ignored);
 	clear_directory(&dir);
 
 	if (advice_status_u_option)