[PATCH] lib: another iterator-temporary/stale-pointer bug

[David Bremner]

Tamas Szakaly points out [1] that the bug fixed in 51b073c still
exists in at least one place. This change follows the suggestion of
[2] and creates a block scope temporary std::string to avoid the rules
of iterators temporaries.

[1]: id:20141226113755.GA64154 at pamparam
[2]: id:20141226230655.GA41992 at pamparam
---

I decided to take a more minimalist approach than [2]. In particular
using "direntry" for two different things seemed slightly trickier
than necessary, for no obvious performance gain (calling .c_str()
should be cheap).

lib/message.cc | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/message.cc b/lib/message.cc
index a7a13cc..bacb4d4 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -641,15 +641,16 @@ _notmuch_message_add_directory_terms (void *ctx, notmuch_message_t *message)
 	unsigned int directory_id;
 	const char *direntry, *directory;
 	char *colon;
+	const std::string term = *i;
 
 	/* Terminate loop at first term without desired prefix. */
-	if (strncmp ((*i).c_str (), direntry_prefix, direntry_prefix_len))
+	if (strncmp (term.c_str (), direntry_prefix, direntry_prefix_len))
 	    break;
 
 	/* Indicate that there are filenames remaining. */
 	status = NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID;
 
-	direntry = (*i).c_str ();
+	direntry = term.c_str ();
 	direntry += direntry_prefix_len;
 
 	directory_id = strtol (direntry, &colon, 10);
-- 
2.1.3