Fixed some subtle bug in the command processing code almost impossible to spot...

Fixed some subtle bug in the command processing code almost impossible to spot in the real world, thanks to gcov

redis.c

@@ -1880,6 +1880,7 @@ again:
             if (sdslen(query) == 0) {
                 /* Ignore empty query */
                 sdsfree(query);
+                if (sdslen(c->querybuf)) goto again;
                 return;
             }
             argv = sdssplitlen(query,sdslen(query)," ",1,&argc);
@@ -1897,10 +1898,16 @@ again:
                 }
             }
             zfree(argv);
-            /* Execute the command. If the client is still valid
-             * after processCommand() return and there is something
-             * on the query buffer try to process the next command. */
-            if (c->argc && processCommand(c) && sdslen(c->querybuf)) goto again;
+            if (c->argc) {
+                /* Execute the command. If the client is still valid
+                 * after processCommand() return and there is something
+                 * on the query buffer try to process the next command. */
+                if (processCommand(c) && sdslen(c->querybuf)) goto again;
+            } else {
+                /* Nothing to process, argc == 0. Just process the query
+                 * buffer if it's not empty or return to the caller */
+                if (sdslen(c->querybuf)) goto again;
+            }
             return;
         } else if (sdslen(c->querybuf) >= REDIS_REQUEST_MAX_SIZE) {
             redisLog(REDIS_DEBUG, "Client protocol error");

test-redis.tcl

@@ -89,6 +89,11 @@ proc main {server port} {
         $r get x
     } {foobar}
 
+    test {SET and GET an empty item} {
+        $r set x {}
+        $r get x
+    } {}
+
     test {DEL against a single item} {
         $r del x
         $r get x
@@ -1229,6 +1234,51 @@ proc main {server port} {
         $r get x
     } {10}
 
+    test {Handle an empty query well} {
+        set fd [$r channel]
+        puts -nonewline $fd "\r\n"
+        flush $fd
+        $r ping
+    } {PONG}
+
+    test {Negative multi bulk command does not create problems} {
+        set fd [$r channel]
+        puts -nonewline $fd "*-10\r\n"
+        flush $fd
+        $r ping
+    } {PONG}
+
+    test {Negative multi bulk payload} {
+        set fd [$r channel]
+        puts -nonewline $fd "SET x -10\r\n"
+        flush $fd
+        gets $fd
+    } {*invalid bulk*}
+
+    test {Too big bulk payload} {
+        set fd [$r channel]
+        puts -nonewline $fd "SET x 2000000000\r\n"
+        flush $fd
+        gets $fd
+    } {*invalid bulk*count*}
+
+    test {Multi bulk request not followed by bulk args} {
+        set fd [$r channel]
+        puts -nonewline $fd "*1\r\nfoo\r\n"
+        flush $fd
+        gets $fd
+    } {*protocol error*}
+
+    test {Generic wrong number of args} {
+        catch {$r ping x y z} err
+        set _ $err
+    } {*wrong*arguments*ping*}
+
+    test {SELECT an out of range DB} {
+        catch {$r select 1000000} err
+        set _ $err
+    } {*invalid*}
+
     # Leave the user with a clean DB before to exit
     test {FLUSHDB} {
         set aux {}
@@ -1322,7 +1372,7 @@ for {set j 0} {$j < [llength $argv]} {incr j} {
         set ::last $arg
         incr j
     } else {
-        echo "Wrong argument: $opt"
+        puts "Wrong argument: $opt"
         exit 1
     }
 }