MDEV-33729 UBSAN negation of -X cannot be represented in type 'long long int';...

MDEV-33729 UBSAN negation of -X cannot be represented in type 'long long int'; cast to an unsigned type to negate this value to itself in my_strntoll_mb2_or_mb4

The problem was introduced by MDEV-30879.
The function my_strntoll_8bit() was correctly changed by MDEV-30879.
The function my_strntoll_mb2_or_mb4() was not.

Applying the missing change to my_strntoll_mb2_or_mb4().

mysql-test/main/ctype_utf32.result

@@ -3024,3 +3024,10 @@ HEX(DATE_FORMAT(TIME'11:22:33',@format))
 #
 # End of 10.4 tests
 #
+#
+# MDEV-33729 UBSAN negation of -X cannot be represented in type 'long long int'; cast to an unsigned type to negate this value to itself in my_strntoll_mb2_or_mb4
+#
+SET NAMES utf8mb3, character_set_connection=utf32;
+SELECT CONV('-AzL8n0Y58m8', -62, -10);
+CONV('-AzL8n0Y58m8', -62, -10)
+-9223372036854775808

mysql-test/main/ctype_utf32.test

@@ -1168,3 +1168,10 @@ SELECT HEX(DATE_FORMAT(TIME'11:22:33',@format));
 --echo #
 
 --enable_service_connection
+
+--echo #
+--echo # MDEV-33729 UBSAN negation of -X cannot be represented in type 'long long int'; cast to an unsigned type to negate this value to itself in my_strntoll_mb2_or_mb4
+--echo #
+
+SET NAMES utf8mb3, character_set_connection=utf32;
+SELECT CONV('-AzL8n0Y58m8', -62, -10);

strings/ctype-ucs2.c

@@ -504,8 +504,12 @@ my_strntoll_mb2_or_mb4(CHARSET_INFO *cs,
   
   if (negative)
   {
-    if (res  > (ulonglong) LONGLONG_MIN)
+    if (res >= (ulonglong) LONGLONG_MIN)
+    {
+      if (res == (ulonglong) LONGLONG_MIN)
+        return LONGLONG_MIN;
       overflow = 1;
+    }
   }
   else if (res > (ulonglong) LONGLONG_MAX)
     overflow = 1;