Trimmed fix for bug #9546 (Crashing with huge decimals)

mysql-test/r/type_newdecimal.result:
  test result fixed
mysql-test/t/type_newdecimal.test:
  test case added
sql/my_decimal.cc:
  error message fixed
strings/decimal.c:
  do_add function fixed

mysql-test/r/type_newdecimal.result

@@ -846,3 +846,14 @@ set sql_mode='';
 select 0/0;
 0/0
 NULL
+select 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 as x;
+x
+999999999999999999999999999999999999999999999999999999999999999999999999999999999
+Warnings:
+Error	1292	Truncated incorrect DECIMAL value: ''
+select 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 + 1 as x;
+x
+NULL
+Warnings:
+Error	1292	Truncated incorrect DECIMAL value: ''
+Error	1292	Truncated incorrect DECIMAL value: ''

mysql-test/t/type_newdecimal.test

@@ -876,3 +876,9 @@ select 10.3330000000000/12.34500000;
 
 set sql_mode='';
 select 0/0;
+
+#
+# bug #9546
+#
+select 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 as x;
+select 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 + 1 as x;

sql/my_decimal.cc

@@ -43,9 +43,9 @@ int decimal_operation_results(int result)
     break;
   case E_DEC_OVERFLOW:
     push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_ERROR,
-			ER_WARN_DATA_OUT_OF_RANGE,
-			ER(ER_WARN_DATA_OUT_OF_RANGE),
-			"", (long)-1);
+                        ER_TRUNCATED_WRONG_VALUE,
+                        ER(ER_TRUNCATED_WRONG_VALUE),
+			"DECIMAL", "");
     break;
   case E_DEC_DIV_ZERO:
     push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_ERROR,

strings/decimal.c

@@ -1612,13 +1612,19 @@ static int do_add(decimal_t *from1, decimal_t *from2, decimal_t *to)
   x=intg1 > intg2 ? from1->buf[0] :
     intg2 > intg1 ? from2->buf[0] :
     from1->buf[0] + from2->buf[0] ;
-  if (unlikely(x > DIG_MASK*9)) /* yes, there is */
+  if (unlikely(x > DIG_MAX-1)) /* yes, there is */
   {
     intg0++;
     to->buf[0]=0; /* safety */
   }
 
   FIX_INTG_FRAC_ERROR(to->len, intg0, frac0, error);
+  if (unlikely(error == E_DEC_OVERFLOW))
+  {
+    max_decimal(to->len * DIG_PER_DEC1, 0, to);
+    return error;
+  }
+
   buf0=to->buf+intg0+frac0;
 
   to->sign=from1->sign;