[PATCH] lib/config: don't set destructor until iterator is initialized.

Subject: [PATCH] lib/config: don't set destructor until iterator is initialized.

Date: Thu, 29 Oct 2020 21:19:10 -0300

To: Olivier Taïbi, notmuch@notmuchmail.org

Cc: David Bremner

From: David Bremner

As diagnosed by Olivier Taïbi in
id:20201027100916.emry3k2wujod4xnl@galois.lan, if an exception is
thrown while the initialization is happening (e.g. if the function is
called on a closed database), then the destructor is (sometimes)
invoked on an uninitialized Xapian object.

Solve the problem by moving the setting of the destructor until after
the placement new successfully completes. It is conceivable this might
cause a memory leak, but that seems preferable to crashing, and in any
case, there seems to be nothing better to be done if the
initialization is failing things are in an undefined state by
definition.
---
 lib/config.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/config.cc b/lib/config.cc
index dae0ff0e..efab01e4 100644
--- a/lib/config.cc
+++ b/lib/config.cc
@@ -113,7 +113,6 @@ notmuch_database_get_config_list (notmuch_database_t *notmuch,
 	goto DONE;
     }
 
-    talloc_set_destructor (list, _notmuch_config_list_destroy);
     list->notmuch = notmuch;
     list->current_key = NULL;
     list->current_val = NULL;
@@ -122,6 +121,7 @@ notmuch_database_get_config_list (notmuch_database_t *notmuch,
 
 	new(&(list->iterator)) Xapian::TermIterator (notmuch->xapian_db->metadata_keys_begin
 							 (CONFIG_PREFIX + (prefix ? prefix : "")));
+	talloc_set_destructor (list, _notmuch_config_list_destroy);
 
     } catch (const Xapian::Error &error) {
 	_notmuch_database_log (notmuch, "A Xapian exception occurred getting metadata iterator: %s.\n",
-- 
2.28.0
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