Date header parsing fails persistently due to aliasing issue in datetok()

I noticed in an optimized build of evolution on Gentoo that parsing date headers always failed. I could track this down to the datetok() implementation in camel-mime-utils.c.

The somewhat fancy singly linked list initialization in this function seems to have aliasing issues:

https://gitlab.gnome.org/GNOME/evolution-data-server/-/blob/9df8f468132e28a42180985b517d96359d295a45/src/camel/camel-mime-utils.c#L4163

datetok() always returns NULL in this case, the compiler does not see tokens changing.

(A disassembly of the code confirms that e.g. a call to parse_rfc822_date is not even present.)

This can be fixed by switching to a more conservative implementation like this, where tokens is clearly written to:

diff --git a/src/camel/camel-mime-utils.c b/src/camel/camel-mime-utils.c
index 6d6cdd1..52707ea 100644
--- a/src/camel/camel-mime-utils.c
+++ b/src/camel/camel-mime-utils.c
@@ -4160,7 +4160,7 @@ struct _date_token {
 static struct _date_token *
 datetok (const gchar *date)
 {
-	struct _date_token *tokens = NULL, *token, *tail = (struct _date_token *) &tokens;
+	struct _date_token *tokens = NULL, *token, *tail = NULL;
 	const gchar *start, *end;
 	guchar mask;
 
@@ -4187,7 +4187,11 @@ datetok (const gchar *date)
 			token->len = end - start;
 			token->mask = mask;
 
-			tail->next = token;
+			if (tail) {
+				tail->next = token;
+			} else {
+				tokens = token;
+			}
 			tail = token;
 		}

If this fix is fine for you, I can create a pull request.