misc: fix warnings with -O3

[elliefm]

There's a bunch of compiler warnings that aren't detected unless certain optimisations are being performed. This PR fixes the warnings that turn up for me using GCC 12.2.0-14 on Debian Bookworm when compiling with -O3 in CFLAGS and CXXFLAGS. If you have a newer compiler to try with, it might find more.

[elliefm]

Back to draft, gonna fix some that turn up with -D_FORTIFY_SOURCE too while I'm in here

[rsto]

I'm using the same compiler version.

[ksmurchison]

I needed to add the patches below for GCC 13.3.1 and 14.1.1. The first to fix an uninitialized var complaint, and the second to fix a citem->s could be NULL complaint.

diff --git a/imap/httpd.c b/imap/httpd.c
index 9625c7c55..7c5372fbb 100644
--- a/imap/httpd.c
+++ b/imap/httpd.c
@@ -3035,7 +3035,7 @@ HIDDEN void log_request(long code, struct transaction_t *txn)
 EXPORTED void response_header(long code, struct transaction_t *txn)
 {
     int i, size;
-    time_t now;
+    time_t now = 0;
     char datestr[30];
     const char **hdr;
     struct auth_challenge_t *auth_chal = &txn->auth_chal;
diff --git a/imap/mbexamine.c b/imap/mbexamine.c
index 39eeb25ea..94da23eef 100644
--- a/imap/mbexamine.c
+++ b/imap/mbexamine.c
@@ -598,20 +598,24 @@ static int do_compare(struct findall_data *data, void *rock)
             r = record ? mailbox_cacherecord(mailbox, record) : -1;
 
             citem = r ? &empty_buf : cacheitem_buf(record, CACHE_FROM);
-            printf("   From: %-50.*s", (int) MIN(citem->len, 50), citem->s);
+            printf("   From: %-50.*s",
+                   (int) MIN(buf_len(citem), 50), buf_cstring(citem));
 
             if (fs_record.uid && !message_guid_isnull(&fs_record.guid)) {
                 citem = cacheitem_buf(&fs_record, CACHE_FROM);
-                printf("\t%-50.*s", (int) MIN(citem->len, 50), citem->s);
+                printf("\t%-50.*s",
+                       (int) MIN(buf_len(citem), 50), buf_cstring(citem));
             }
             printf("\n");
 
             citem = r ? &empty_buf : cacheitem_buf(record, CACHE_SUBJECT);
-            printf("   Subj: %-50.*s", (int) MIN(citem->len, 50), citem->s);
+            printf("   Subj: %-50.*s",
+                   (int) MIN(buf_len(citem), 50), buf_cstring(citem));
 
             if (fs_record.uid && !message_guid_isnull(&fs_record.guid)) {
                 citem = cacheitem_buf(&fs_record, CACHE_SUBJECT);
-                printf("\t%-50.*s", (int) MIN(citem->len, 50), citem->s);
+                printf("\t%-50.*s",
+                       (int) MIN(buf_len(citem), 50), buf_cstring(citem));
             }
             printf("\n");
             printf("\n");

[ksmurchison]

Need to add the diff that I supplied

[elliefm]

Thanks!

[ksmurchison]

WFM

[elliefm]

I thought I was going to fix these warnings and then work on the actual problem separately, but the two wound up entangled and it no longer makes sense to keep them separate, so I'm closing this one off.

This work, as well as the actual bug fix, are now in #4980