From: Date: March 15 2005 2:15pm
Subject: bk commit into 4.1 tree (bar:1.2120) BUG#8785
List-Archive: http://lists.mysql.com/internals/23036
X-Bug: 8785
Message-Id: <200503151315.j2FDFr5x004660@bar.intranet.mysql.r18.ru>

Below is the list of changes that have just been committed into a local
4.1 repository of bar. When bar does a push these changes will
be propagated to the main repository and, within 24 hours after the
push, to the public repository.
For information on how to access the public repository
see http://dev.mysql.com/doc/mysql/en/installing-source-tree.html

ChangeSet
  1.2120 05/03/15 17:15:47 bar@stripped +5 -0
  # Bug#8785 Problem with nested concats and
  character set conversion of a string constant.

  sql/sql_string.h
    1.55 05/03/15 17:15:43 bar@stripped +4 -0
    A new method to cut Alloced_length to str_length for
    string constants, to avoid reusing them as a buffer
    in things like CONCAT().

  sql/item_strfunc.cc
    1.220 05/03/15 17:15:43 bar@stripped +1 -2
    Remove previous fix: it was not 100% correct.
    A non const_item() can return a constant String.

  sql/item.cc
    1.194 05/03/15 17:15:43 bar@stripped +12 -0
    # Bug#8785 Problem with nested concats and
    character set conversion of a string constant.

  mysql-test/t/ctype_utf8.test
    1.50 05/03/15 17:15:43 bar@stripped +9 -0
    Addign test

  mysql-test/r/ctype_utf8.result
    1.50 05/03/15 17:15:43 bar@stripped +7 -0
    Adding test

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	bar
# Host:	bar.intranet.mysql.r18.ru
# Root:	/usr/home/bar/mysql-4.1

--- 1.193/sql/item.cc	2005-03-09 18:50:57 +04:00
+++ 1.194/sql/item.cc	2005-03-15 17:15:43 +04:00
@@ -236,6 +236,18 @@
     return NULL;
   }
   conv->str_value.copy();
+  /* 
+    The above line executes str_value.realloc() internally,
+    which alligns Alloced_length using ALLIGN_SIZE.
+    In the case of Item_string::str_value we don't want
+    Alloced_length to be longer than str_length.
+    Otherwise, some functions like Item_func_concat::val_str()
+    try to reuse str_value as a buffer for concatenation result
+    for optimization purposes, so our string constant become
+    corrupted. See bug#8785 for more details.
+    Let's shrink Alloced_length to str_length to avoid this problem.
+  */
+  conv->str_value.shrink_to_length();
   return conv;
 }
 

--- 1.219/sql/item_strfunc.cc	2005-03-09 22:37:24 +04:00
+++ 1.220/sql/item_strfunc.cc	2005-03-15 17:15:43 +04:00
@@ -277,8 +277,7 @@
 			    current_thd->variables.max_allowed_packet);
 	goto null;
       }
-      if (!args[0]->const_item() && 
-          res->alloced_length() >= res->length()+res2->length())
+      if (res->alloced_length() >= res->length()+res2->length())
       {						// Use old buffer
 	res->append(*res2);
       }

--- 1.54/sql/sql_string.h	2005-02-15 04:55:37 +04:00
+++ 1.55/sql/sql_string.h	2005-03-15 17:15:43 +04:00
@@ -177,6 +177,10 @@
       }
     }
   }
+  inline void shrink_to_length()
+  {
+    Alloced_length= str_length;
+  }
   bool is_alloced() { return alloced; }
   inline String& operator = (const String &s)
   {

--- 1.49/mysql-test/r/ctype_utf8.result	2005-02-21 17:17:13 +04:00
+++ 1.50/mysql-test/r/ctype_utf8.result	2005-03-15 17:15:43 +04:00
@@ -861,6 +861,13 @@
 one	<one>
 two	<two>
 DROP TABLE t1;
+create table t1 (f1 varchar(1) not null) default charset utf8;
+insert into t1 values (''), ('');
+select concat(concat(_latin1'->',f1),_latin1'<-') from t1;
+concat(concat(_latin1'->',f1),_latin1'<-')
+-><-
+-><-
+drop table t1;
 select convert(_koi8r'É' using utf8) < convert(_koi8r'Ê' using utf8);
 convert(_koi8r'É' using utf8) < convert(_koi8r'Ê' using utf8)
 1

--- 1.49/mysql-test/t/ctype_utf8.test	2005-02-21 17:17:10 +04:00
+++ 1.50/mysql-test/t/ctype_utf8.test	2005-03-15 17:15:43 +04:00
@@ -695,6 +695,15 @@
 DROP TABLE t1;
 
 #
+# Bug#8785
+# the same problem with the above, but with nested CONCATs
+#
+create table t1 (f1 varchar(1) not null) default charset utf8;
+insert into t1 values (''), ('');
+select concat(concat(_latin1'->',f1),_latin1'<-') from t1;
+drop table t1;
+
+#
 # Bug#8385: utf8_general_ci treats Cyrillic letters I and SHORT I as the same
 #
 select convert(_koi8r'É' using utf8) < convert(_koi8r'Ê' using utf8);