On Tuesday 19 September 2006 10:47, Joost van der Sluis wrote: > Run it in a debugger and tell us on which line it crashes? The backtrace says it crashes on line 96 - the mysql_query call, I ran it through gdb and got the following output:
(gdb) run
Starting program: /tmp/project1
[Thread debugging using libthread_db enabled]
[New Thread 16384 (LWP 10618)]
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 16384 (LWP 10618)]
0x40321a08 in mysql_slave_send_query () from /usr/lib/libmysqlclient.so.14
>
> And you're using the mysql4 unit. You know what the consequences are?
> What's the version of you're mysql-client?
Consequences ? I understood that you needed mysql4 for versions after
mysql-version 3.
I have mysql version 4.1.13.
Should I be using a different unit name ?
>
> (And ask yourself: do I really want to use mysql?)
This one I haven't got much choice over. It has to be a network transparent
SQL server, and it has to be something just about every distro comes with,
and which people know how to use - and some of the component parts will quite
possible be written in other languages like PHP (this isn't fixed but quite
likely).
>
> On Tue, 2006-09-19 at 10:13 +0200, A.J. Venter wrote:
> > Mmm,
> > So does nobody know what I'm doing wrong ? Or is it not a problem in my
> > code ? Any idea what I should check ?
> >
> > A.J.
> >
> > On Monday 18 September 2006 15:17, A.J. Venter wrote:
> > > I have just started on a new project, which is mysql backed - beginning
> > > with a fairly abstract unit which a large number of different lazarus
> > > programs will use to communicate with the DB.
> > >
> > > But I ran into a very strange problem quite early on, I can connect to
> > > the DB without hassles, but as soon as I try to do a query - I get a
> > > crash, and I have no idea why... :S
> > >
> > > My current test calls look like this:
> > >
> > > ZC_DBConnect;
> > > ZC_Settings : TZC_Settings.Create;
> > > Writeln(ZC_Settings.GetPricePerUnit);
> > >
> > > TraceBack says it's crashing on line 96:
> > > if (mysql_query(socket,pchar(Query)) < 0) then
> > >
> > >
> > > The unit in full goes:
> > > unit libzybacafe;
> > >
> > > {$mode objfpc}{$H+}
> > >
> > > interface
> > >
> > > uses
> > > Classes, SysUtils,dialogs,mysql4;
> > >
> > > procedure ZC_DBConnect;
> > > Function ZC_DBQuery(Query:String):PMYSQL_RES;
> > >
> > > type
> > > TZC_Settings = class
> > > private
> > > {Private Declarations}
> > > FCurrencySymbol : String;
> > > FUnitLength : Integer;
> > > FPricePerUnit : Real;
> > > FResult : PMySQL_RES;
> > > FRow: MYSQL_ROW;
> > > Procedure LoadFromDB;
> > > Procedure SaveToDB;
> > > public
> > > { public declarations }
> > > Function GetCurrencySymbol : String;
> > > Function GetUnitLength : Integer;
> > > Function GetPricePerUnit: Real;
> > > Procedure SetCurrencySymbol(NewSymbol:String);
> > > Procedure SetUnitLength(NewLength:Integer);
> > > Procedure SetPricePerUnit(NewPrice : Real);
> > > end;
> > >
> > > Var
> > > Socket : PMysQL;
> > >
> > > implementation
> > >
> > > procedure ZC_DBConnect;
> > > Var
> > > DBCFG : TSTringList;
> > > I : Integer;
> > > H,U,P,D : String;
> > > qmysql : TMYSQL;
> > > alloc : PMYSQL;
> > >
> > > Begin
> > > DBCFG := TSTringList.Create;
> > > Try
> > > {$IFDEF Unix}
> > > DBCFG.LoadFromFile('/etc/zybacafe.cfg');
> > > {$ENDIF}
> > > {$IFDEF Win32}
> > > DBCFG.LoadFromFile('C:\Program Files\ZybaCafe\zybacafe.cfg');
> > > {$ENDIF}
> > > except
> > > ShowMessage ('Error Loading database configuration !');
> > > Halt;
> > > end;
> > > For I := 0 to DBCFG.Count -1 do
> > > begin
> > > If pos('HOST=',uppercase(DBCFG[I])) <> 0 then
> > > begin
> > > H := DBCFG[I];
> > > Delete(H,1,pos('=',H));
> > > end;
> > > If pos('USERNAME=',uppercase(DBCFG[I])) <> 0 then
> > > begin
> > > U := DBCFG[I];
> > > Delete(U,1,pos('=',U));
> > > end;
> > > If pos('PASSWORD=',uppercase(DBCFG[I])) <> 0 then
> > > begin
> > > P := DBCFG[I];
> > > Delete(P,1,pos('=',P));
> > > end;
> > > If pos('DATABASE=',uppercase(DBCFG[I])) <> 0 then
> > > begin
> > > D := DBCFG[I];
> > > Delete(D,1,pos('=',D));
> > > end;
> > >
> > > end;
> > > alloc := mysql_init(PMYSQL(@qmysql));
> > > socket := mysql_real_connect(alloc, pchar(h), pchar(u),
> > > pchar(p),pchar(d), 0, nil, 0);
> > > if socket=Nil then
> > > begin
> > > ShowMessage('Error connecting to
> > > database:'+LineEnding+StrPas(mysql_error(@qmysql)));
> > > halt;
> > > end;
> > > end;
> > >
> > > Function ZC_DBQuery(Query:String):PMYSQL_RES;
> > > Var RecBuf : PMYSQL_RES;
> > > Begin
> > > if (mysql_query(socket,pchar(Query)) < 0) then
> > > begin
> > > ShowMessage('Query failed '+ StrPas(mysql_error(socket)));
> > > end
> > > else
> > > begin
> > > recbuf := mysql_store_result(socket);
> > > if RecBuf=Nil then
> > > begin
> > > ShowMessage('Query returned nil result.');
> > > end else
> > > ZC_DBQuery := RecBuf;
> > > end;
> > > end;
> > >
> > > Procedure TZC_Settings.LoadFromDB;
> > > Var Result : PMYSQL_RES;
> > > Q : String;
> > > Begin
> > > FResult := ZC_DBQuery('SELECT * FROM settings;');
> > > FRow := Mysql_Fetch_Row(FResult);
> > > If FRow = Nil then
> > > begin
> > > showMessage('You have no stored
> > > site-settings.'+LineEnding+'Setting all to defaults');
> > > FCurrencySymbol := '$';
> > > FUnitLength := 1;
> > > FPricePerUnit := 1.0;
> > > Q := 'INSERT INTO settings VALUES("","'+FCurrencySymbol;
> > > Q :=
> > > Q+'","'+IntToStr(FUnitLength)+'","'+FloatToStr(FPricePerUnit)+'");';
> > > Result := ZC_DBQuery(Q);
> > > end else
> > > begin
> > > FCurrencySymbol := FRow[1];
> > > FUnitLength := StrToInt(FRow[2]);
> > > FPricePerUnit := StrToFloat(FRow[3]);
> > > end;
> > >
> > > end;
> > >
> > > Procedure TZC_Settings.SaveToDB;
> > > Var
> > > Query : String;
> > > Begin
> > > Query := 'UPDATE TABLE settings SET
> > > currencysymbol="'+FCurrencySymbol; Query :=
> > > Query+'",unitlength="'+IntToStr(FUnitLength);
> > > Query := Query+'",priceperunit="'+FloatToStr(FPricePerUnit)+';';
> > > FResult := ZC_DBQuery(Query);
> > > end;
> > >
> > > Function TZC_Settings.GetCurrencySymbol : String;
> > > Begin
> > > LoadFromDB;
> > > GetCurrencySymbol := FCurrencySymbol;
> > > end;
> > >
> > > Function TZC_Settings.GetUnitLength : Integer;
> > > Begin
> > > LoadFromDB;
> > > GetUnitLength := FUnitLength;
> > > end;
> > >
> > > Function TZC_Settings.GetPricePerUnit: Real;
> > > Begin
> > > LoadFromDB;
> > > GetPricePerUnit := FPricePerUnit;
> > > end;
> > >
> > > Procedure TZC_Settings.SetCurrencySymbol(NewSymbol:String);
> > > Begin
> > > FCurrencySymbol := NewSymbol;
> > > SaveToDB;
> > > end;
> > >
> > > Procedure TZC_Settings.SetUnitLength(NewLength:Integer);
> > > Begin
> > > FUnitLength := NewLength;
> > > SaveToDB;
> > > end;
> > >
> > > Procedure TZC_Settings.SetPricePerUnit(NewPrice : Real);
> > > Begin
> > > FPricePerUnit := NewPrice;
> > > SaveToDB;
> > > end;
> > >
> > > initialization
> > >
> > >
> > > end.
--
"80% Of a hardware engineer's job is application of the uncertainty principle.
80% of a software engineer's job is pretending this isn't so."
A.J. Venter
Chief Software Architect
OpenLab International | +27 83 455 99 78 (South Africa)
http://www.getopenlab.com | 086 654 2898 (Fax)
http://www.silentcoder.co.za | +55 118 162 2079 (Brazil)
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