Hypermail could crash or created an incorrect mail thread if a message and its reply were archived in wrong order.

Author: jkbzh

Changelog

@@ -4,6 +4,13 @@ Version Changes for Hypermail
 HYPERMAIL VERSION 2.3.1:
 ============================
 
+ Jose Kahan (June 14, 2018)
+  - Hypermail would segfault or have an incorrect thread view if it was
+    handling an archive with a message (msg1) that was a reply to a message not
+    in the archive, if msg1 had a reply to it in the archive (msg2), msg2 was
+    archived before msg1 and both msg1 and msg2 shared the same subject
+    (regardless of Re: prefixes).
+
  Bill Shannon (June 7, 2018)
   - Add charset alias for Thai and Chinese
   - The markup for access key "j" to jump to the start of a message

src/parse.c

@@ -354,10 +354,21 @@ void crossindex(void)
 				    &maybereply);
 	if (status != -1) {
 	    struct emailinfo *email2;
+            
 	    if (!hashnumlookup(status, &email2)) {
 		++num;
 		continue;
 	    }
+	    /*  make sure there is no recursion between the message
+                and reply lookup if a message and its reply-to were
+                archived in reverse, both messages share the same
+                subject (regardless of Re), and the message itself was
+                a reply to a non-archived message. */
+	    if (maybereply && !strcmp (email2->inreplyto, email->msgid)) {
+                ++num;
+                continue;
+            }
+            
 	    if (set_linkquotes) {
 	        struct reply *rp;
 		int found_num = 0;