Fix for BUG#9298: Make int->string conversion sign-aware in Protocol_simple::store_long

mysql-test/r/group_by.result:
  Testcase for BUG#9298
mysql-test/t/group_by.test:
  Testcase for BUG#9298

mysql-test/r/group_by.result

@@ -702,3 +702,12 @@ c
 val-74
 val-98
 drop table t1,t2;
+create table t1 (b int4 unsigned not null);
+insert into t1 values(3000000000);
+select * from t1;
+b
+3000000000
+select min(b) from t1;
+min(b)
+3000000000
+drop table t1;

mysql-test/t/group_by.test

@@ -515,3 +515,10 @@ explain select c from t2 where a = 2 and b = 'val-2' group by c;
 select c from t2 where a = 2 and b = 'val-2' group by c;
 drop table t1,t2;
 
+# Test for BUG#9298 "Wrong handling of int4 unsigned columns in GROUP functions"
+# (the actual problem was with protocol code, not GROUP BY)
+create table t1 (b int4 unsigned not null);
+insert into t1 values(3000000000);
+select * from t1;
+select min(b) from t1;
+drop table t1;

sql/protocol.cc

@@ -810,7 +810,7 @@ bool Protocol_simple::store_long(longlong from)
 #endif
   char buff[20];
   return net_store_data((char*) buff,
-			(uint) (int10_to_str((int) from,buff, -10)-buff));
+			(uint) (int10_to_str((int)from,buff, (from <0)?-10:10)-buff));
 }