Merge gbichot@213.136.52.20:/home/bk/mysql-4.1

into mysql.com:/home/mysql_src/mysql-4.1

sql/slave.cc

@@ -2060,10 +2060,29 @@ int show_master_info(THD* thd, MASTER_INFO* mi)
     protocol->store(mi->ssl_key, &my_charset_bin);
 
     if (mi->rli.last_master_timestamp)
-      protocol->store((ulonglong) 
-                      (long)((time_t)time((time_t*) 0)
-                             - mi->rli.last_master_timestamp)
-                      - mi->clock_diff_with_master);
+    {
+      long tmp= (long)((time_t)time((time_t*) 0)
+                               - mi->rli.last_master_timestamp)
+        - mi->clock_diff_with_master;
+      /*
+        Apparently on some systems tmp can be <0. Here are possible reasons
+        related to MySQL:
+        - the master is itself a slave of another master whose time is ahead.
+        - somebody used an explicit SET TIMESTAMP on the master.
+        Possible reason related to granularity-to-second of time functions
+        (nothing to do with MySQL), which can explain a value of -1:
+        assume the master's and slave's time are perfectly synchronized, and
+        that at slave's connection time, when the master's timestamp is read,
+        it is at the very end of second 1, and (a very short time later) when
+        the slave's timestamp is read it is at the very beginning of second
+        2. Then the recorded value for master is 1 and the recorded value for
+        slave is 2. At SHOW SLAVE STATUS time, assume that the difference
+        between timestamp of slave and rli->last_master_timestamp is 0
+        (i.e. they are in the same second), then we get 0-(2-1)=-1 as a result.
+        This confuses users, so we don't go below 0.
+      */
+      protocol->store((longlong)(max(0, tmp)));
+    }
     else
       protocol->store_null();