MDEV-29154 Excessive warnings upon a call to RANDOM_BYTES

Bring the 5 warnings of select random_bytes(cast('x' as unsigned)+1);
back to two. 1 for Item_func_random_bytes::fix_length_and_dec and
one from Item_func_random_bytes::val_str.

The warnings are from args[0]->val_int().

mysql-test/main/func_str.result

@@ -5327,5 +5327,20 @@ SELECT RANDOM_BYTES(-10) f1, IFNULL(a,1) f2 FROM t GROUP BY f1, f2;
 ERROR 22003: length value is out of range in 'random_bytes(-10)'
 DROP TABLE t;
 #
+# MDEV-29154: Excessive warnings upon a call to RANDOM_BYTES
+#
+select length(random_bytes(cast('x' as unsigned)+1));
+length(random_bytes(cast('x' as unsigned)+1))
+1
+Warnings:
+Warning	1292	Truncated incorrect INTEGER value: 'x'
+Warning	1292	Truncated incorrect INTEGER value: 'x'
+select repeat('.', cast('x' as unsigned)+1);
+repeat('.', cast('x' as unsigned)+1)
+.
+Warnings:
+Warning	1292	Truncated incorrect INTEGER value: 'x'
+Warning	1292	Truncated incorrect INTEGER value: 'x'
+#
 # End of 10.10 tests
 #

mysql-test/main/func_str.test

@@ -2259,6 +2259,13 @@ SELECT RANDOM_BYTES(-10) f1, IFNULL(a,1) f2 FROM t GROUP BY f1, f2;
 # Cleanup
 DROP TABLE t;
 
+--echo #
+--echo # MDEV-29154: Excessive warnings upon a call to RANDOM_BYTES
+--echo #
+
+select length(random_bytes(cast('x' as unsigned)+1));
+select repeat('.', cast('x' as unsigned)+1);
+
 --echo #
 --echo # End of 10.10 tests
 --echo #

sql/item_strfunc.cc

@@ -1478,14 +1478,13 @@ String *Item_func_sformat::val_str(String *res)
 #include <openssl/rand.h>
 #include <openssl/err.h>
 
-static const int MAX_RANDOM_BYTES= 1024;
-
 bool Item_func_random_bytes::fix_length_and_dec(THD *thd)
 {
   used_tables_cache|= RAND_TABLE_BIT;
   if (args[0]->can_eval_in_optimize())
   {
-    max_length= MY_MAX(0, MY_MIN((int32) args[0]->val_int(), MAX_RANDOM_BYTES));
+    int32 v= (int32) args[0]->val_int();
+    max_length= MY_MAX(0, MY_MIN(v, MAX_RANDOM_BYTES));
     return false;
   }
   max_length= MAX_RANDOM_BYTES;

sql/item_strfunc.h

@@ -406,6 +406,7 @@ class Item_func_random_bytes : public Item_str_func
   {
     return get_item_copy<Item_func_random_bytes>(thd, this);
   }
+  static const int MAX_RANDOM_BYTES= 1024;
 };