Fix for the bug #1333: COMPRESS(NULL) segfaults.

BitKeeper/etc/logging_ok

@@ -97,6 +97,7 @@ peter@linux.local
 peter@mysql.com
 peterg@mysql.com
 pgulutzan@linux.local
+ram@gw.mysql.r18.ru
 ram@gw.udmsearch.izhnet.ru
 ram@mysql.r18.ru
 ram@ram.(none)

mysql-test/r/func_compress.result

@@ -40,3 +40,9 @@ uncompress(compress(""))
 select uncompressed_length("");
 uncompressed_length("")
 0
+select compress(NULL);
+compress(NULL)
+NULL
+select uncompress(NULL);
+uncompress(NULL)
+NULL

mysql-test/t/func_compress.test

@@ -23,3 +23,9 @@ select uncompress("");
 select uncompress(compress(""));
 select uncompressed_length("");
 
+#
+# NULL (Bug #1333)
+#
+
+select compress(NULL);
+select uncompress(NULL);

sql/item_strfunc.cc

@@ -2539,6 +2539,11 @@ longlong Item_func_crc32::val_int()
 String *Item_func_compress::val_str(String *str)
 {
   String *res= args[0]->val_str(str);
+  if (!res)
+  {
+    null_value= 1;
+    return 0;
+  }
   if (res->is_empty()) return res;
 
   int err= Z_OK;
@@ -2589,6 +2594,11 @@ String *Item_func_compress::val_str(String *str)
 String *Item_func_uncompress::val_str(String *str)
 {
   String *res= args[0]->val_str(str);
+  if (!res)
+  {
+    null_value= 1;
+    return 0;
+  }
   if (res->is_empty()) return res;
 
   ulong new_size= uint4korr(res->c_ptr()) & 0x3FFFFFFF;