From 74c64904c7e1730d77fe8a525f14aed3ad9df0b5 Mon Sep 17 00:00:00 2001
From: "ram@gw.mysql.r18.ru" <>
Date: Thu, 12 Aug 2004 11:28:39 +0500
Subject: [PATCH] A fix (Bug #4878: Service crashes on query execution)

---
 mysql-test/r/func_str.result | 3 +++
 mysql-test/t/func_str.test   | 6 ++++++
 sql/item_strfunc.cc          | 5 ++++-
 sql/sql_string.h             | 1 +
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/mysql-test/r/func_str.result b/mysql-test/r/func_str.result
index e07ee4f0add..345832387bd 100644
--- a/mysql-test/r/func_str.result
+++ b/mysql-test/r/func_str.result
@@ -673,3 +673,6 @@ c1	c2
 2147483647	4294967295
 -2147483648	0
 drop table t1;
+select left(1234, 3) + 0;
+left(1234, 3) + 0
+123
diff --git a/mysql-test/t/func_str.test b/mysql-test/t/func_str.test
index 61d0326f7dd..e7852df40b3 100644
--- a/mysql-test/t/func_str.test
+++ b/mysql-test/t/func_str.test
@@ -402,3 +402,9 @@ insert into t1 values ('-21474836461','-21474836461');
 show warnings;
 select * from t1;
 drop table t1;
+
+#
+# Bug #4878: LEFT() in integer/float context
+#
+
+select left(1234, 3) + 0;
diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index d3493e1fad1..995627766c0 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -984,7 +984,10 @@ String *Item_func_left::val_str(String *str)
     return &my_empty_string;
   if (res->length() <= (uint) length)
     return res;
-  str_value.set(*res, 0, res->charpos(length));
+  if (&str_value == res)
+    str_value.length(res->charpos(length));
+  else
+    str_value.set(*res, 0, res->charpos(length));
   return &str_value;
 }
 
diff --git a/sql/sql_string.h b/sql/sql_string.h
index 01329c45a98..0179b3ebadc 100644
--- a/sql/sql_string.h
+++ b/sql/sql_string.h
@@ -98,6 +98,7 @@ public:
 
   void set(String &str,uint32 offset,uint32 arg_length)
   {
+    DBUG_ASSERT(&str != this);
     free();
     Ptr=(char*) str.ptr()+offset; str_length=arg_length; alloced=0;
     if (str.Alloced_length)