MySQL Bugs: #30770: Access Violation in myodbc3.dll

Bug #30770	Access Violation in myodbc3.dll
Submitted:	3 Sep 2007 12:40	Modified:	8 Jul 2008 9:04
Reporter:	Dietmar Augsten	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / ODBC	Severity:	S2 (Serious)
Version:	3.51.17 up	OS:	Windows (XP SP2)
Assigned to:	Bogdan Degtyariov	CPU Architecture:	Any
Tags:	3.51, 5.1, av, odbc_postga51

Description:
If I use a ADOConnection and will try to open a schema with ADOConnection.OpenSchema an access violation in myodbc3.dll will occur.

This error occurs in 3.51.17 and 3.51.19 but 3.51.14 works fine. Also 5.0.11 works fine.

Server version 5.0.45

How to repeat:
Sorry, not in VB or C but Delphi

var sC : TADoConnection;
    tableName : String;
    DS : TADODataSet;
    aServer,aPort,aUser,aPwd,aDatabase: String;
...
sC.ConnectionString   := 'Provider=MSDASQL.1;DRIVER={MySQL ODBC 3.51 Driver}'+
                         ';SERVER ='+aServer+
                         ';PORT   ='+aPort+
                         ';OPTION =3'+
                         ';UID    ='+aUser+
                         ';PWD    ='+aPwd;
sC.Open;
...
sC.ConnectionObject.Execute('USE ' + aDatabase, O, adCmdText + adExecuteNoRecords);
...
DS := TADODataSet.Create(Nil);
sC.OpenSchema(siColumns, VarArrayOf([Unassigned, Unassigned, tablename, Unassigned]), EmptyParam, DS);

=> AV in myodbc3.dll (adress 020BE5D0 for 3.51.17)

Could you attach to this bug report a manager trace log
when it works and when it doesn't? Would help a lot.

Hi Dietmar and thanks for your report. I have no problem with Delphi.

Can you please do as Kent suggested and attach:
 - my.ini/cnf
 - Full Delphi test case
 - ODBC DM trace

what is the version of Delphi you're using? Are you going through BDE?

Delphi using: Delphi 6 and Delphi 2006. Runnig in IDE or compiled by commandline-bcc32 and runnig after it. All four combinations will show the same error. 

Logs, and i hope so a testcace, will follow later this day.

ODBC log

Attachment: odbclog.zip (application/x-zip-compressed, text), 85.57 KiB.

Dietmar, this suits me perfectly as I have both versions. Waiting on test case.

Testcase Delphi incl. logs and my.ini

Attachment: Testcase_Delphi_Src.zip (application/x-zip-compressed, text), 15.43 KiB.

AV also in ver 3.51.20

Dietmar, yes, and in 5.1 too... I will need some time to figure out what's going on behind the scene.

Dietmar, VBS test case passes but it has 1 significant difference from your test case, it searches for table names by itself:

option explicit
dim connectionString : connectionString = "DSN=myodbccln;uid=root;pwd=***"
' Open ADO connection
Dim Conn : set conn = CreateObject("ADODB.Connection")
conn.ConnectionString = connectionString
conn.Open
conn.Execute "USE tst1"
conn.Execute "USE tst2"
dim txt : txt = ""
Dim TablesSchema : Set TablesSchema = Conn.OpenSchema(20) ' this line is also used in the plugin
Do While Not TablesSchema.EOF
  dim tableName : tableName = TablesSchema("TABLE_NAME")
  txt = txt & tableName & VBCRLF & " -> "
  'Get all columns of the current table
  Dim ColumnsSchema : Set ColumnsSchema = Conn.OpenSchema(4, Array(Empty, Empty,tableName))
  ' Add all channels
  Do While Not ColumnsSchema.EOF
    dim columnName : columnName = ColumnsSchema("COLUMN_NAME")
    txt = txt & columnName & ";"
    ColumnsSchema.MoveNext
  Loop
  txt = txt & VBCRLF
  ' Next table
  TablesSchema.MoveNext
Loop
MsgBox txt

Can you try and mimic this in your Delphi app and see if it works (i.e. do not send table_name but rewrite function to loop through retrieved table names)?

a possible alternative in Delphi would be
function GetFieldList(table: String; sC : TADoConnection): String;
VAR DS, DS2    : TADODataSet;
    name       : ShortString;
    AT         : TADOTable;
    lokTable   : OLEVariant;
    lokTableStr: String;
BEGIN
  DS  := TADODataSet.Create(Nil);
  DS2 := TADODataSet.Create(Nil);
  result := '';
  try
    DS.Recordset := sC.ConnectionObject.OpenSchema(adSchemaTables,VarArrayOf([Unassigned, Unassigned, Unassigned, Unassigned]), EmptyParam);
    DS.First;

    WHILE NOT DS.Eof DO BEGIN
      lokTableStr := DS.FieldByName('TABLE_NAME').Value;
      if AnsiUpperCase(lokTableStr) = AnsiUpperCase(table) then
      begin
        StrPCopy(lokTable,DS.FieldByName('TABLE_NAME').Value);
        DS2.Recordset := sC.ConnectionObject.OpenSchema(adSchemaColumns,VarArrayOf([Unassigned, Unassigned, Unassigned, DS.FieldByName('TABLE_NAME').Value]), EmptyParam);
        WHILE NOT DS2.Eof DO BEGIN
          name := DS2.FieldByName('COLUMN_NAME').AsString;
          if result = '' then
            result := name
          else
            result := result + ', '+name;
        END;
      end;
      DS.Next;
    END;
  except
  end;
  DS.Free;
  DS2.Free;
end;

The outer OpenSchema works, but the inner shows the "normal" AV.

Same here...

Verified as described, traces & test cases already attached.

Imo, this has got to do with CodeGear implementation of ADO, not MyODBC per se, but will see what dev's have to say.

Access Violation occurs in SQLColumns:

TestmySQL       9f0-100 ENTER SQLColumnsW
                HSTMT               02C02510
                WCHAR *             0x00000000 [ -3] <empty string>
                SWORD                       -3
                WCHAR *             0x00000000 [ -3] <empty string>
                SWORD                       -3
                WCHAR *             0x023B7990 [ -3] "sqlabfragen\ 0"
                SWORD                       -3
                WCHAR *             0x00000000 [ -3] <empty string>
                SWORD                       -3

patch and test case

Attachment: patch30770.diff (application/octet-stream, text), 2.05 KiB.

looks good, but i would change 0 to NULL in the new ?: expression.

The patch has been committed to the source repository. Will be included in MyODBC 3.51.26

An entry has been added to the 3.51.26 Changelog:

When an ADOConnection is created and attempts to open a schema with ADOConnection.OpenSchema an access violation occurs in myodbc3.dll.