The Wiert Corner – irregular stream of stuff

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

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Archive for the ‘Software Development’ Category

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delphi – Why variables are declared as TStrings and created as TStringList? – Stack Overflow

Posted by jpluimers on 2019/07/24

Blast from the past: [WayBack] delphi – Why variables are declared as TStrings and created as TStringList? – Stack Overflow

Q

Why variables are declared as TStrings and created as TStringList?

A

Because that way you could put another TStrings descendant in the SL variable (I’d probably call that Strings, not SL).

In your case, that is moot, since the logic around SL contains the creation of a TStringList and no external assignment or parameter parsing.

But if you ever split the logic away from the assignment, then you could benefit from using any TStrings descendant.

For instance, a TMemoy.Lines, TListBox.Items, TComboBox.Items, etc.
From the outside it looks like they are TStrings, but internally they do not use a TStringList but their own descendant.

A few examples of classes that descend from TStrings:

source\DUnit\Contrib\DUnitWizard\Source\DelphiExperts\Common\XP_OTAEditorUtils.pas:
     TXPEditorStrings = class(TStrings)
source\fmx\FMX.ListBox.pas:
       TListBoxStrings = class(TStrings)
source\fmx\FMX.Memo.pas:
     TMemoLines = class(TStrings)
source\rtl\common\System.Classes.pas:
     TStringList = class(TStrings)
source\vcl\Vcl.ComCtrls.pas:
     TTabStrings = class(TStrings)
     TTreeStrings = class(TStrings)
     TRichEditStrings = class(TStrings)
source\vcl\Vcl.ExtCtrls.pas:
     TPageAccess = class(TStrings)
     THeaderStrings = class(TStrings)
source\vcl\Vcl.Grids.pas:
     TStringGridStrings = class(TStrings)
     TStringSparseList = class(TStrings)
source\vcl\Vcl.Outline.pas:
     TOutlineStrings = class(TStrings)
source\vcl\Vcl.StdCtrls.pas:
     TCustomComboBoxStrings = class(TStrings)
     TMemoStrings = class(TStrings)
     TListBoxStrings = class(TStrings)
source\vcl\Vcl.TabNotBk.pas:
     TTabPageAccess = class(TStrings)

–jeroen

Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | 1 Comment »

PowerShell script header to be as strict as possible and always throw exceptions

Posted by jpluimers on 2019/07/24

This is my default PowerShell script header from now on:

Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'
$PSDefaultParameterValues['*:ErrorAction']='Stop'

This might sound like overkill, but it solves these problems:

The above helped me tremendously with for instance [WayBack] powershell – Why does the exception not get me in the catch block? – Stack Overflow:

I’m trying to interrogate some service information. Sometimes the installer of the application fails to correctly install, so the registry does not contain a service entry. I want to find out which installer steps did get executed correctly, even on systems that do not have proper logging in the installer.

If MyService does not exist, the script below does not go to the catch block even though the exception handling documentation suggests a bare catch should be enough:

try {
    $path = 'hklm:\SYSTEM\CurrentControlSet\services\MyService'
    $key = Get-Item $path
    $namevalues = $key | Select-Object -ExpandProperty Property |
        ForEach-Object {
        [PSCustomObject] @{
            Name = $_;
            Value = $key.GetValue($_)
        }
    }
    $namevalues | Format-Table
}
catch {
    $ProgramFilesX86 = [System.Environment]::GetFolderPath("ProgramFilesX86");
    $ProgramFiles = [System.Environment]::GetFolderPath("ProgramFiles");
    Write-Host $ProgramFilesX86
    Write-Host $ProgramFiles
}

Why is that and how should I force it to end up in the catch?

This is what PowerShell outputs:

Get-Item : Cannot find path 'HKLM:\SYSTEM\CurrentControlSet\services\MyService' because it does not exist.
At C:\Users\Developer\...\GetMyServiceInfo.ps1:17 char:12
+     $key = Get-Item $path
+            ~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (HKLM:\SYSTEM\Cu...vices\MyService:String) [Get-Item], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetItemCommand

For which I edited the answer to become this:

Force the error to be terminating:

$key = Get-Item $path -ErrorAction Stop

That way it will throw and catch will get it.

Explanation and links to the official Microsoft documentation:

What is missing there is the link to the $PSDefaultParameterValues documentation at [WayBack] about_Parameters_Default_Values | Microsoft Docs

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

Laptop fan profiling, and debugging them – related to Profiling | CommitStrip

Posted by jpluimers on 2019/07/23

A while back, I posted the “profiling” CommitStrip on[WayBack] Profiling – Jeroen Wiert Pluimers – Google+. Boy how did I not know that within a week, I bumped into a “laptop fan profiling” artefact.

A coworker noticed, that when starting a thread based equivalent of [WayBack] TTimer Class (which cannot be used in services as it depends on the VCL), then sometimes the laptop fans would spin up.

What basically happened was that for certain combinations of Enabled and Interval the Execute would loop burning 100% of one CPU core.

With 3 or more – sometimes 2 – of these threads active on a 4+4 core (4 are hyper-threaded), the processor fan would start to spin like madness.

Finding the solution was somewhat easy too:

  • Process Explorer would show the thread IDs burning the most CPU cycles
  • Delphi shows the Thread IDs in the Thread Status pane (if they are named, the ID is at the end of the name in parenthesis)
  • At around Delphi 2010, you can Freeze or Thaw threads. This allows you to debug only a single thread by freezing all others.

Focussing on one thread, allowed a close inspection of the loop, quickly finding the actual cause and repairing it.

TTimer Thread

A similar and better class is at [WayBack] multithreading – TTimerThread – Threaded timer class – Code Review Stack Exchange, based on [WayBack] timer – Using VCL TTimer in Delphi console application – Stack Overflow.

Read the rest of this entry »

Posted in Conference Topics, Conferences, Debugging, Delphi, Development, Event, Fun, Multi-Threading / Concurrency, Profiling-Performance-Measurement, Software Development | Leave a Comment »

Namespaces in Delphi – Stack Overflow

Posted by jpluimers on 2019/07/23

Blast from the past, but still relevant: [WayBack] Namespaces in Delphi – Stack Overflow:

Q

Are there any practical benefits in using long unit file names like MyLib.MyUtils.pas or it is just a kind of unit name prefix?

A

Namespaces, like all identifiers, are meant to organize.

So using them, only benefits if your project gets organized in a better way. This is highly subjective matter (there have been ‘wars’ on even the most simple naming conventions!), so impossible to really answer.

[WayBack] Here is some documentation on how namespaces work in Delphi.

Note that ‘true’ namespaces (where more than one generic DLL can contribute to the same namespace; this is how namespaces function in the .NET world) are not possible in Delphi: you could go the BPL way, but that is not the same as a ‘generic DLL’. This is not a limitation of Delphi itself, but the way that native DLLs in Windows ‘work’.

–jeroen

Posted in Delphi, Development, Software Development | Leave a Comment »

DTW-DanWard/PowerShell-Beautifier: A whitespace reformatter and code cleaner for Windows PowerShell and PowerShell Core

Posted by jpluimers on 2019/07/23

Interesting tool: DTW-DanWard/PowerShell-Beautifier: A whitespace reformatter and code cleaner for Windows PowerShell and PowerShell Core

–jeroen

via: [WayBack] Is there a PowerShell code formatter / pretty printer? – Stack Overflow

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

Technical debt: “taking shortcuts leads to long-term bleeding…”

Posted by jpluimers on 2019/07/19

From a while ago:

Just tried to explain technical debt: “taking shortcuts leads to long-term bleeding.”

[WayBack] – Jeroen Wiert Pluimers – Google+

–jeroen

Posted in Development, Software Development, Technical Debt | Leave a Comment »

delphi – How to hide the inherited TObject constructor while the class has overloaded ones? – Stack Overflow

Posted by jpluimers on 2019/07/18

Interesting, need to try this one day to see how well this works so the base constructor TObject.Create cannot be called.[WayBack] delphi – How to hide the inherited TObject constructor while the class has overloaded ones? – Stack Overflow

–jeroen

Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | Leave a Comment »

PowerShell: Format-Table to show all columns/members

Posted by jpluimers on 2019/07/18

I’m not even sure if I’ve posted this before, but I always forget how to show all members (or columns) using Format-Table.

It’s dead easy: -Property *

Get-ChildItem | Format-Table -Property *

Later I found out this is equivalent with the shorter version where you omit the -Property part which I wrote about in [WayBack] PowerShell: when Format-Table -AutoSize displays only 10 columns and uses the width of the console when redirecting to file.

So you can shorten the above to:

Get-ChildItem | Format-Table *

It has way more columns than this:

Get-ChildItem | Format-Table

The extra members in both marked with *:

  • PSPath
  • PSParentPath
  • PSChildName
  • PSDrive
  • PSProvider
  • PSIsContainer
  • BaseName
  • Mode *
  • Name *
  • FullName
  • Parent
  • Exists
  • Root
  • Extension
  • CreationTime
  • CreationTimeUtc
  • LastAccessTime
  • LastAccessTimeUtc
  • LastWriteTime *
  • LastWriteTimeUtc
  • Attributes

The odd thing: one property fails in the -Property * table:

  • Length

I tracked this down to how -Property * works: it takes the first entry in the list. If that is not a file, then it has no Length property: [WayBack] powershell – Measure-Object : The property “length” cannot be found in the input for any objects – Stack Overflow.

Note that for a GUI version, you can replace Format-Table with Out-GridView. See

–-jeroen.

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

Threads are not the answer | CompuTruthing

Posted by jpluimers on 2019/07/17

Long read, but worth it: [WayBack] Threads are not the answer | CompuTruthing

We argue that the thread-oriented approach to concurrency is a bad approach. It has severe modifiability problems, but also performance problems. We should not think in terms of low level primitives.

It has great analogies between threading and cars on roads:

Software world Automotive world
thread road
work unit set of cars that pass over a road in a period of time
work unit dependencies cars need to go from one road to another
total execution time total time for all cars to reach the destination
lock/semaphore traffic lights / roundabout
too few work unit dependencies (highway) road network badly connected (sometimes this means long way to nearby locations)
too many work unit dependencies too many intersections or access points (too much time spent in these)
too many small threads (descheduled often) small roads
threads that are not descheduled from cores highways

Via

[WayBack] Kevlin Henney – Google+ 

Related videos under the fold (more at DevTube – Videos by @kevlinhenney)

–jeroen

Read the rest of this entry »

Posted in Development, Multi-Threading / Concurrency, Software Development | Leave a Comment »

Tweaked TStringBuilder in FastCode is now 2x faster than the stock…

Posted by jpluimers on 2019/07/17

Reminder to self as occasionally I concatenate a lot of strings:

[WayBack] After some tweaking TStringBuilder in FastCode is now 2x faster than the stock Builder in SysUtils.  – Johan Bontes – Google+.

Source: FastCode/FastStringBuilder.pas at master · JBontes/FastCode

–jeroen

Posted in Delphi, Development, Software Development | Leave a Comment »

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