bzr commit into mysql-5.0-bugteam branch (joro:2725) Bug#41437

[Georgi Kodinov]

#At file:///home/kgeorge/mysql/work/B41437-5.0-bugteam/ based on revid:joro@stripped

 2725 Georgi Kodinov	2009-01-09
      Bug #41437: Value stored in 'case' lacks charset, causes segfault
      
      When substituting system constant functions with a constant result
      the server was not expecting that the function may return NULL.
      Fixed by checking for NULL and returning Item_null (in the relevant
      collation) if the result of the system constant function was NULL.
modified:
  mysql-test/r/mysql.result
  mysql-test/t/mysql.test
  sql/item_strfunc.cc

per-file messages:
  mysql-test/r/mysql.result
    Bug #41437: test case
  mysql-test/t/mysql.test
    Bug #41437: test case.
    Relies on database() returning NULL if no database is
    selected.
  sql/item_strfunc.cc
    Bug #41437: Check for NULL result on evaluating the system
    constant function and return a constant NULL item.
=== modified file 'mysql-test/r/mysql.result'
--- a/mysql-test/r/mysql.result	2008-12-11 17:26:03 +0000
+++ b/mysql-test/r/mysql.result	2009-01-09 11:50:18 +0000
@@ -186,4 +186,6 @@ delimiter
 2
 2
 2
+@z:='1'	@z=database()
+1	NULL
 End of 5.0 tests

=== modified file 'mysql-test/t/mysql.test'
--- a/mysql-test/t/mysql.test	2008-12-11 17:26:03 +0000
+++ b/mysql-test/t/mysql.test	2009-01-09 11:50:18 +0000
@@ -309,4 +309,9 @@ EOF
 --exec $MYSQL -c < $MYSQLTEST_VARDIR/tmp/bug38158.sql 2>&1
 remove_file $MYSQLTEST_VARDIR/tmp/bug38158.sql;
 
+#
+# Bug #41437: Value stored in 'case' lacks charset, causees segfault
+#
+--exec $MYSQL -e "select @z:='1',@z=database()"
+
 --echo End of 5.0 tests

=== modified file 'sql/item_strfunc.cc'
--- a/sql/item_strfunc.cc	2008-07-10 23:51:58 +0000
+++ b/sql/item_strfunc.cc	2009-01-09 11:50:18 +0000
@@ -1696,6 +1696,12 @@ Item *Item_func_sysconst::safe_charset_c
   Item_string *conv;
   uint conv_errors;
   String tmp, cstr, *ostr= val_str(&tmp);
+  if (null_value)
+  {
+    Item *null_item= new Item_null((char *) fully_qualified_func_name());
+    null_item->collation.set (tocs);
+    return null_item;
+  }
   cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(), tocs, &conv_errors);
   if (conv_errors ||
       !(conv= new Item_static_string_func(fully_qualified_func_name(),