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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for October 10th, 2018

linux – dmesg time vs system time time isnt correct – Server Fault

Posted by jpluimers on 2018/10/10

[WayBack] linux – dmesg time vs system time time isnt correct – Server Fault helped me solve this problem with an Odroid C1+ running busybox:

[root@meye-062016b9 ~]# hwclock --show
Wed Apr  3 20:25:47 2013  0.000000 seconds
[root@meye-062016b9 ~]# date
Wed May 31 09:48:18 UTC 2018
[root@meye-062016b9 ~]# hwclock --systohc --utc
[root@meye-062016b9 ~]# hwclock --show
Wed May 31 09:48:29 2018  0.000000 seconds
[root@meye-062016b9 ~]# date
Wed May 31 09:48:35 UTC 2018
[root@meye-062016b9 ~]#

Note: If your logging clock in /var/log/dmesg.log is wrong by an exact couple of hours, then try [WayBack] syslog time wrong – but date returns the correct time? and edit [WayBack] /etc/sysconfig/clock.

The above involves looking if I can get MotionEyeOS working Giving up on the official Ubuntu for Odroid C1 image.

So far not much luck: the Ubuntu got hosed, but before it was stable as in that didn’t reboot suddenly.

Now the MotionEyeOS (which is busybox based) reboots itself without notice about every 3 minutes, despite no other hardware connected and trying 3 different power supplies.

The Odroid C1+ only draws 0.34 Ampère at 5.13 Volt which is well within specs.

I’m puzzled:

[Wed May 31 09:49:51 2018] Booting Linux on physical CPU 0x200
[Wed May 31 09:52:20 2018] Booting Linux on physical CPU 0x200
[Wed May 31 09:54:50 2018] Booting Linux on physical CPU 0x200
[Wed May 31 09:57:19 2018] Booting Linux on physical CPU 0x200
[Wed May 31 09:59:49 2018] Booting Linux on physical CPU 0x200
[Wed May 31 10:02:22 2018] Booting Linux on physical CPU 0x200
[Wed May 31 10:04:56 2018] Booting Linux on physical CPU 0x200
[Wed May 31 10:07:26 2018] Booting Linux on physical CPU 0x200
[Wed May 31 10:09:59 2018] Booting Linux on physical CPU 0x200
[Wed May 31 10:12:29 2018] Booting Linux on physical CPU 0x200
[Wed May 31 10:14:58 2018] Booting Linux on physical CPU 0x200

—jeroen

Posted in *nix, *nix-tools, Power User | Leave a Comment »

TObjectHelper for easier debugging a cast mismatch and a typed FreeAndNil

Posted by jpluimers on 2018/10/10

The below came in really useful in an old project I took over that was full of bugs having to do with improper casts and FreeAndNil usage.

EDIT 20181010: WordPress.com keeps mangling angle-brackets in pre and code sections, so I added the code to a gist; see link below.

First the examples.

procedure TMyServer.UnbindFromIdTcpServerStatusContext(const aContext: TIdContext);
var
  lClientSession: TClientSession;
begin
  lClientSession := TObjectHelper.Cast<TClientSession>(aContext.Data);
...
end;

type
  TBaseDataInterface = class(TObject)
  strict private
    FDatabase:      TIBDatabase;
    FTransaction:   TIBTransaction;
...
  end;


destructor TBaseDataInterface.Destroy();
begin
  TObjectHelper.FreeAndNil(FDatabase);
  TObjectHelper.FreeAndNil(FTransaction);
...
  inherited Destroy();
end;

And the implementation.

unit ObjectHelperUnit;

interface

type
  TObjectHelper = record
    class function Cast<T: class>(const aValue: TObject): T; static;
    class procedure FreeAndNil<T: class>(var Value: T); static;
  end;

implementation

uses
  System.SysConst,
  System.SysUtils;

class function TObjectHelper.Cast<T>(const aValue: TObject): T;
var
  lException: Exception;
begin
  if Assigned(aValue) then
  begin
    if aValue is T then
      Result := T(aValue)
    else
    begin
      lException := EInvalidCast.CreateFmt('%s; actual type %s but expected %s.',
        [SInvalidCast, aValue.QualifiedClassName, T.QualifiedClassName]);
      raise lException;
    end;
  end
  else
    Result := nil;
end;

class procedure TObjectHelper.FreeAndNil<T>(var Value: T);
begin
  System.SysUtils.FreeAndNil(Value);
end;

end.

–jeroen

Gist:


unit ObjectHelperUnit;
interface
type
TObjectHelper = record
class function Cast<T: class>(const aValue: TObject): T; static;
class procedure FreeAndNil<T: class>(var Value: T); static;
end;
implementation
uses
System.SysConst,
System.SysUtils;
class function TObjectHelper.Cast<T>(const aValue: TObject): T;
var
lException: Exception;
begin
if Assigned(aValue) then
begin
if aValue is T then
Result := T(aValue)
else
begin
lException := EInvalidCast.CreateFmt('%s; actual type %s but expected %s.',
[SInvalidCast, aValue.QualifiedClassName, T.QualifiedClassName]);
raise lException at ReturnAddress;
end;
end
else
Result := nil;
end;
class procedure TObjectHelper.FreeAndNil<T>(var Value: T);
begin
System.SysUtils.FreeAndNil(Value);
end;
end.

view raw

ObjectHelperUnit.pas

hosted with ❤ by GitHub


procedure TMyServer.UnbindFromIdTcpServerStatusContext(const aContext: TIdContext);
var
lClientSession: TClientSession;
begin
lClientSession := TObjectHelper.Cast<TClientSession>(aContext.Data);
…
end;
type
TBaseDataInterface = class(TObject)
strict private
FDatabase: TIBDatabase;
FTransaction: TIBTransaction;
…
end;
destructor TBaseDataInterface.Destroy();
begin
TObjectHelper.FreeAndNil(FDatabase);
TObjectHelper.FreeAndNil(FTransaction);
…
inherited Destroy();
end;

view raw

UsageExample.pas

hosted with ❤ by GitHub

Posted in Delphi, Development, Software Development | 16 Comments »

 
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