[Lazarus] is it me or a bug that i ve been fighting?
Martin Friebe
lazarus at mfriebe.de
Mon Jan 19 02:02:38 CET 2009
Hi,
let me start with "No I have not executed the demo code";
but a couple of thinks that come to mind:
1) What version of FPC are you using (you only said you updated
Lazarus); you refer to FPC 2.2.2, have you tried the fixes branch
(2.2.3)? or trunc(2.3.1)?
2) You say you do not know the exact error: " because the popup box
doesn't state it" => Try running the exe in the debugger, make sure you
compile with debug symbols for gdb (-g, maybe also -gl).
Or try to compile "not" as a windows app (switch off -WG) then you get a
console window, and a lot of output.
(Both options are in Project->compiler options->tab: linking)
It could be in the RTL, in which case it would be helpful to rebuild
this with debug support
Good Luck
waldo kitty wrote:
> thanks for your response, reenen... it does tend to make sense on the one hand
> but on the other i "must" ask if you have looked at and/or run the demo code i
> pointed to?
>
> it does check if the connection is open ;)
>
> procedure TFormTryMySQL.ConnectButtonClick(Sender: TObject);
> begin
> // Check if we have an active connection. If so, let's close it.
> if MySQLConnection1.Connected then begin
> SQLTransaction1.Active := False;
> MySQLConnection1.Close;
> end;
> blahfooblah...;
>
> when i place logging lines in the above, the last logging line that executes is
> the one right above "MySQLConnection1.Close;" which indicates the error in is
> the "MySQLConnection1.Close;" library code...
>
> i can see where what you are saying may be possible but it doesn't make sense
> because the next time the above is executed, it works "properly" (ie: there's no
> error)..
>
> what it almost sounds like is that in closing the connection object, something
> was not created during the open which somehow does get created during the close...
>
> again, i dunno and that's why i'm here... one would think that demo code should
> work and work properly (ie: without error) out of the box... i won't point back
> to my comment about having problems with several other of the wiki demo apps not
> working for some reason or another :?
>
>
>
> Reenen Laurie wrote:
>
>> I am very uninformed when it comes to databases, but access violations
>> happens when you do stuff to stuff that's not there.
>>
>> My guess is that for some reason your "close" code gets fired twice, and
>> thus it's already closed by the time you get there the second time.
>>
>> So if there's a way to check if it's open, before you close it, I'd
>> suggest try to close it inside an if open...
>>
>> Regards,
>> -Reenen
>>
>> On Sun, Jan 18, 2009 at 9:39 PM, waldo kitty <wkitty42 at windstream.net
>> <mailto:wkitty42 at windstream.net>> wrote:
>>
>>
>> history: i'm a long time pascal coder... since TP3 first appeared on the
>> market... then to TP5 and most of my time with TP6/BP6 and numerous
>> commercial
>> apps under my belt... i've dabbled with OOP stuffs, TP7/BP7 and even
>> have a copy
>> of delphi6-personal that i've not been able to wrap my head
>> around... since my
>> delphi was a downloaded copy from Inprise, it is also a bit harder
>> to work with
>> since i've no real documentation that i can lay in my lap to look
>> over while
>> working on code :? :(
>>
>> in any case, i've been fighting a battle with mysql50conn for a few
>> weeks,
>> now... i started with Lazaruz 0.9.26 and last night installed
>> Lazarus 0.9.27 to
>> see if the problem i'm facing may have been fixed in there but it
>> has not and
>> i'm not even certain if the problem is in the library code or
>> possibly something
>> on this old win98SE box :?
>>
>> ok, enough of the history and story telling...
>>
>> the details: with the tutorial DB code on the wiki (yeah, i was
>> /finally/ able
>> to get two or three of those working after some starts, stops and
>> fits :P),
>> there's several that check to see if the connection to the database
>> is active
>> and if it is, they attempt to close it... my problem is that the
>> first attempt
>> to close the connection _always_ throws an error... i don't know
>> what specific
>> error code because the popup box doesn't state it... the box only says
>>
>> Access violation.
>>
>> Press Ok to ignore and risk data corruption.
>> Press Cancel to kill the program.
>>
>> [OK] [Cancel]
>>
>> i'm triggering my initial connection to the database via a button. i
>> click the
>> button, the connection takes place, data is retrieved, and the
>> connection is
>> attempted to close... that's when the error is thrown... however, if
>> i hit the
>> [OK] button to ignore the error then i can open and close the
>> connection to the
>> database with no problems... at least it appears that way because
>> other routines
>> gather other data from other tables and they all connect, gather,
>> and disconnect
>> without problems... all routines use the very same disconnect
>> routine and this
>> is what leads be to believe that there's something in the library
>> code that's
>> the problem...
>>
>> currently, all the code i'm using simply uses the close procedure of the
>> connection object (ie: MySQL50Connection.Close)... i've only one
>> graphical demo
>> app that doesn't exhibit this problem but it is using mysql4 in the
>> uses and a
>> lot of manual code instead of the connector, transaction, and sqlquery
>> objects... i also have the text modedemo app working and it doesn't
>> have the
>> problems either... now, i'm not sure, at all, if any of the (demo)
>> apps i'm
>> working with are using the libmysql.dll file that i placed in my
>> windows/system(32?) directory or not... i believe that the textmode
>> demo would
>> not run without that dll but that was several weeks ago when i was
>> playing with
>> it and it was also in the plain FPC 2.2.2 installation i have/had on
>> here before
>> i figured out that Laz came with FPC in its tree...
>>
>> for those who want/need a link to example code that exhibits this
>> problem, i'm
>> using the downloaded code "TryMySQL5 Modified by Arwen" but i can't
>> find the
>> link in the wiki now :( in any case, this is the TryMySQL5 demo app
>> with the
>> fields for the server, username, and password rather than them being
>> hardcoded... once you fill them in, then you click the [Connect]
>> button to
>> connect to the server and get a list of available databases... now
>> you choose a
>> database from the combo box and then click the [Select Database]
>> button... it is
>> at this point that the error is thrown when the connection is closed and
>> reopened so the new database can be used...
>>
>>
>> FWIW:
>> here's the memo field "log" with the error point marked with '>>'
>> and yes, i've
>> slightly modified the "logging" to try to figure out where the error
>> is taking
>> place and every time the last line logged before the popup box
>> appears is the
>> one right above the mysql50connection.close line...
>>
>> 14:26:18: Opening a connection to server: ender
>> 14:26:19: Connected to server: ender
>> 14:26:19: Retreiving list of available databases.
>> 14:26:19: Query ACTIVE and at the first record
>> 14:26:19: List of databases received!
>> >>14:26:26: Closing connection
>> 14:26:33: Closing connection
>> 14:26:33: Connection closed...
>> 14:26:33: DatabaseComboBox.ItemIndex: 2
>> 14:26:33: DatabaseComboBox.Items[ItemIndex]: kims
>> 14:26:33: setting SQL statement...
>> 14:26:33: Retrieving list of tables
>> 14:26:33: opening sql query...
>> 14:26:34: List of tables received
>>
>> so, at 14:26:26, i clicked the [Select Database] button and then
>> clicked the
>> [OK] button in the error box and then i clicked on the [Select
>> Database] button
>> again (14:26:33)...
>>
>> so, there it is with all my wordiness and verbiage... oh, and the
>> hidden subtle
>> "am i linked?" test message ;)
>>
>> so, is it me or is it a bug in the library? if the library, which
>> library? Laz
>> stuff or FPC stuff?
>>
>> --
>> NOTE: NEW EMAIL ADDRESS!!
>>
>> _\/
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>
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