Bug #24947: REPEAT function returns NULL when passed a field as the count parameter

Handling of large signed/unsigned values was not consistent, so some string functions could return bogus results.
The current fix is to simply patch up the val_str() methods for those string items.
It would be good clean this code up in general, to make similar problems much harder to make.  This is left as an exercise for the reader.

mysql-test/r/func_str.result

@@ -1916,4 +1916,16 @@ CHAR(0xff,0x8f USING utf8) IS NULL
 Warnings:
 Error	1300	Invalid utf8 character string: 'FF8F'
 SET SQL_MODE=@orig_sql_mode;
+select substring('abc', cast(2 as unsigned int));
+substring('abc', cast(2 as unsigned int))
+bc
+select repeat('a', cast(2 as unsigned int));
+repeat('a', cast(2 as unsigned int))
+aa
+select rpad('abc', cast(5 as unsigned integer), 'x');
+rpad('abc', cast(5 as unsigned integer), 'x')
+abcxx
+select lpad('abc', cast(5 as unsigned integer), 'x');
+lpad('abc', cast(5 as unsigned integer), 'x')
+xxabc
 End of 5.0 tests

mysql-test/t/func_str.test

@@ -991,5 +991,13 @@ SELECT CHAR(0xff,0x8f USING utf8) IS NULL;
 
 SET SQL_MODE=@orig_sql_mode;
 
+#
+# Bug #24947: problem with some string function with unsigned int parameters
+#
+
+select substring('abc', cast(2 as unsigned int));
+select repeat('a', cast(2 as unsigned int));
+select rpad('abc', cast(5 as unsigned integer), 'x');
+select lpad('abc', cast(5 as unsigned integer), 'x');
 
 --echo End of 5.0 tests

sql/item_strfunc.cc

@@ -1166,7 +1166,8 @@ String *Item_func_substr::val_str(String *str)
 
   /* if "unsigned_flag" is set, we have a *huge* positive number. */
   /* Assumes that the maximum length of a String is < INT_MAX32. */
-  if ((args[1]->unsigned_flag) || (start < INT_MIN32) || (start > INT_MAX32))
+  if ((!args[1]->unsigned_flag && (start < INT_MIN32 || start > INT_MAX32)) ||
+      (args[1]->unsigned_flag && ((ulonglong) start > INT_MAX32)))
     return &my_empty_string;
 
   start= ((start < 0) ? res->numchars() + start : start - 1);
@@ -2227,25 +2228,23 @@ String *Item_func_repeat::val_str(String *str)
   uint length,tot_length;
   char *to;
   /* must be longlong to avoid truncation */
-  longlong tmp_count= args[1]->val_int();
-  long count= (long) tmp_count;
+  longlong count= args[1]->val_int();
   String *res= args[0]->val_str(str);
 
-  /* Assumes that the maximum length of a String is < INT_MAX32. */
-  /* Bounds check on count:  If this is triggered, we will error. */
-  if ((tmp_count > INT_MAX32) || args[1]->unsigned_flag)
-    count= INT_MAX32;
-
   if (args[0]->null_value || args[1]->null_value)
     goto err;				// string and/or delim are null
   null_value= 0;
-  if ((tmp_count <= 0) && !args[1]->unsigned_flag)	// For nicer SQL code
+  if ((count <= 0) && !args[1]->unsigned_flag)	// For nicer SQL code
     return &my_empty_string;
+  /* Assumes that the maximum length of a String is < INT_MAX32. */
+  /* Bounds check on count:  If this is triggered, we will error. */
+  if ((ulonglong) count > INT_MAX32)
+    count= INT_MAX32;
   if (count == 1)			// To avoid reallocs
     return res;
   length=res->length();
   // Safe length check
-  if (length > current_thd->variables.max_allowed_packet/count)
+  if (length > current_thd->variables.max_allowed_packet / (uint) count)
   {
     push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN,
 			ER_WARN_ALLOWED_PACKET_OVERFLOWED,
@@ -2319,15 +2318,14 @@ String *Item_func_rpad::val_str(String *str)
   String *res= args[0]->val_str(str);
   String *rpad= args[2]->val_str(&rpad_str);
 
+  if (!res || args[1]->null_value || !rpad || 
+      ((count < 0) && !args[1]->unsigned_flag))
+    goto err;
+  null_value=0;
   /* Assumes that the maximum length of a String is < INT_MAX32. */
   /* Set here so that rest of code sees out-of-bound value as such. */
-  if ((count > INT_MAX32) || args[1]->unsigned_flag)
+  if ((ulonglong) count > INT_MAX32)
     count= INT_MAX32;
-
-  if (!res || args[1]->null_value || !rpad || count < 0)
-    goto err;
-  null_value=0;
-
   if (count <= (res_char_length= res->numchars()))
   {						// String to pad is big enough
     res->length(res->charpos((int) count));     // Shorten result if longer
@@ -2421,14 +2419,15 @@ String *Item_func_lpad::val_str(String *str)
   String *res= args[0]->val_str(&tmp_value);
   String *pad= args[2]->val_str(&lpad_str);
 
+  if (!res || args[1]->null_value || !pad ||  
+      ((count < 0) && !args[1]->unsigned_flag))
+    goto err;  
+  null_value=0;
   /* Assumes that the maximum length of a String is < INT_MAX32. */
   /* Set here so that rest of code sees out-of-bound value as such. */
-  if ((count > INT_MAX32) || args[1]->unsigned_flag)
+  if ((ulonglong) count > INT_MAX32)
     count= INT_MAX32;
 
-  if (!res || args[1]->null_value || !pad || count < 0)
-    goto err;
-  null_value=0;
   res_char_length= res->numchars();
 
   if (count <= res_char_length)