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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System.SyncObjs.TLightweightSemaphore.Create: the AInitialCount parameter

Posted by jpluimers on 2020/12/16

Multi-threading is hard, knowing your primitives is important, but Embarcadero documentation is always far from complete, leading to [WayBack] System.SyncObjs.TLightweightSemaphore.Create: Please simply explain to me the parameters of this constructor, especially first, AInitialCount… – Jacek Laskowski – Google+

The concept of semaphores is universal (the free book [WayBack] The Little Book of Semaphores – Green Tea Press is great), but the implementation/wrapping can slightly differ, so on the [Archive.is] XE introduced TLightweightSemaphore.Create parameters:

  • Primož Gabrijelčič's profile photo
    Primož Gabrijelčič+2

    Semaphore is used to allow ‘counted’ access. It allows access to as much owners as it has maximum count. If you wait on a semaphore (WaitFor) and wait succeeds, the semaphore’s count is decremented. When it drops to 0, no new Wait will succeed.

    When you call Release, the semaphore’s count is incremented which allows somebody else to own the semaphore.

    Parameters simply set the initial state for this count and maximum value of the counter. Usually you’ll both set to the same value.

  • Primož Gabrijelčič's profile photo
    Primož Gabrijelčič

    If you intend to use semaphores, read this. Great book.

    The Little Book of Semaphores – Green Tea Press
    greenteapress.com
  • Jacek Laskowski's profile photo
    Jacek Laskowski
    I know (theoretically) how a semaphore works. I even used this semaphore class in production code.
    I want to create as many threads as there are cores in the processor (+ 1 additional, little loaded).fCoreController := TLightweightSemaphore.Create(TThread.ProcessorCount, TThread.ProcessorCount + 1);But now it turned out that customers who have CPUs with one core (yes, there are those), this code blocks the remaining threads. And I am looking for a reason, maybe I misunderstand this semaphore. What does AInitialCount mean?

    ps. Delphi Seattle

  • Stefan Glienke's profile photo
    Stefan Glienke
    AInitialCount is the number of entires a semaphore has left when created. If that is one less than AMaxCount that means you already gave one entry away. I just do a wild guess and say that you might do a Wait on the created semaphore shortly after creating it and in some other thread as well but since for one CPU your AInitialCount is only 1, one of them will block – possibly you created a deadlock situation here.
  • Jacek Laskowski's profile photo
    Jacek Laskowski
    +Stefan Glienke Ok, if I want threads to be given a semaphore so that they work when it’s open (thread execute -> Semaphor.WaitFor) and I want to have as many threads as there are cores (+1 additional) then how should I create TLightweightSemaphore object?
  • Stefan Glienke's profile photo
    Stefan Glienke
    What Primoz said at the end of the very first comment – put same value for both: TThread.ProcessorCount + 1
  • Jacek Laskowski's profile photo
    Jacek Laskowski

 

–jeroen

 

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

Alternatives to UUID/GUID as database keys

Posted by jpluimers on 2020/12/15

For my link archive:

–jeroen

Posted in Database Development, Development, PostgreSQL, Software Development | Leave a Comment »

I really wish people reporting bugs provide more factual details, especially when asked for

Posted by jpluimers on 2020/12/15

Basically the below thread goes like this: [WayBack] GExperts / Bugs / #92 Grep cannot handle UTF-16 and UTF-32 pas files

  1. There is a bug in UTF-16 and UTF-32 handling in your tool when running under AAA, but  not when running your tool under BBB; these files fail: xxx.txt  and yyy.txt
  2. Which version of our tool did you run under AAA and which version of our tool did you run under BBB
  3. It fails with your tool when running under AAA , but succeeds under BBB
  4. Repeat at step 2 until you fall asleep.

Part of the [WayBack] Short, Self Contained, Correct Example are indeed in it, but without more details it is hard to reproduce.

So without the reporter providing those details, nobody, especially not on open source projects, is going to fix it just on that bug report.

Via: [WayBack] It’s time for a gift to all Delphi developers, a new Release of GExperts. Happy Holidays! (But do spend some time with your family rather than testing G… – Thomas Mueller (dummzeuch) – Google+

Which highlights another conceptual problem from the same bug reporter: expecting a new version to have a regression of all open bugs against the new version.

That’s not how the world works, if it has ever worked that way. If your issue is not mentioned in any release notes, then assume nothing happened. If you want to bump it up, then provide more details.

–jeroen

Posted in Conference Topics, Conferences, Development, Event, How to report bugs, Issue/Bug tracking, Software Development | Leave a Comment »

In Delphi, avoid having a TComponent descendant implement interfaces, unless you are prepared to handle your refcounting

Posted by jpluimers on 2020/12/15

Every now and then I see code, where a class descending from TComponent implements some interfaces, only interface references are used to the instances, and the expected behaviour is that the instances will free themselves when all the references went out of scope.

Bummer: TComponent by default is not reference counted.

It is when you assign VCLComObject an IVCLComObject which is hell to implement (Delphi provides two of them: TVCLAutoObject and TActiveFormControl. They sound heavey, and are).

Do not go that way. If you need some form of ownership in a class implementing an interface, then descend the class from TInterfacedObject, and add a field of TComponent that is the owner of things that need to be freed later on. In the destructor, free that field.

Something like this:

unit InterfacedObjectWithRootUnit;

interface

type
   TInterfacedObjectWithRoot = class(TInterfacedObject)
   strict private
      FRoot: TComponent;
      function GetRoot: TComponent;
   strict protected
      property Root: TComponent read GetRoot;
   public
      destructor Destroy; override;
   end;

implementation

destructor TInterfacedObjectWithRoot.Destroy;
begin
  if Assigned(FRoot) then
  begin
    FRoot.Free();
    FRoot := nil;
  end;
  inherited Destroy();
end;

function TInterfacedObjectWithRoot.GetRoot: TComponent;
begin
  if FRoot = nil then
    FRoot := TComponent.Create(nil);
  Result := FRoot;
end;

end.

–jeroen

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

Why We Should Change The Rhythm Of Business | Corporate Rebels

Posted by jpluimers on 2020/12/11

This should be on the reading list of every corporate manager: [WayBack] Why We Should Change The Rhythm Of Business | Corporate Rebels:

The problem arises when people bring their accounting background and mindset with them into business management. Decimals no longer works very well when the focus is on a future with lots of dynamics and uncertainty.

…

The solution is simple: (1) Targets must have natural deadlines; (2) Forecasting must be dynamic or rolling; (3) Resource allocation must be dynamic; and (4) Performance evaluation must take place when work is completed.

Or as Marjan Venema quoted:

“Yes, something is definitely wrong, but maybe more in the finance manager’s head than with the fisherman’s work rhythm!”

–jeroen

via: [WayBack] “Yes, something is definitely wrong, but maybe more in the finance manager’s head than with the fisherman’s work rhythm!” – Marjan Venema – Google+

Posted in Development, LifeHacker, Power User, Software Development | Leave a Comment »

On Windows 7 and 8.x too: Completely disable Windows 10 telemetry collection – twm’s blog

Posted by jpluimers on 2020/12/10

From [WayBack] Completely disable Windows 10 telemetry collection – twm’s blog:

So I don’t forget: According to an article in c’t magazine, disabling the “DiagTrack” service (“Connected User Experience and Telemetry”) will completely disable user tracking in Windows 10. They also say that they did not see any negative effects.

Source: [WayBack] Telefonierverbot in c’t 01/2019 page 172 (in German)

I saw at least one system where the service is not shown when you run Services.msc: it did not list DiagTrack, nor Connected User Experience and Telemetry. How awful is that!

The service can also be installed non older Windows versions: [WayBack] Just found DiagTrack running in Services – Tips and Tricks

Sometimes, it gets re-enabled. I think this happens during major Windows updates.

To inspect, stop and disable

Run all commands from the console the below bold commands. The non-bold text was the output on my system. If instead of the cmd.exe console, you run a PowerShell console, then remove the bits PowerShell -Command " and " at the start and end of each command.

The first command does not require an Administrative (UAC Elevated) command prompt; the last one does.

However, the first command, needs the | Select-Object * bit as otherwise most of the fields will not be displayed, excluding for instance StartType.

powershell -Command "Get-Service -Name DiagTrack | Select-Object *"


Name                : DiagTrack
RequiredServices    : {RpcSs}
CanPauseAndContinue : False
CanShutdown         : True
CanStop             : True
DisplayName         : Connected User Experiences and Telemetry
DependentServices   : {}
MachineName         : .
ServiceName         : DiagTrack
ServicesDependedOn  : {RpcSs}
ServiceHandle       :
Status              : Running
ServiceType         : Win32OwnProcess
StartType           : Automatic
Site                :
Container           :

On an Administrative command-prompt:

powershell -Command "Set-Service -Name DiagTrack -StartUpType Disabled"
powershell -Command "Get-Service -Name DiagTrack | Stop-Service"

Two notes:

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Posted in Batch-Files, CommandLine, Development, Power User, PowerShell, PowerShell, Scripting, Software Development, Windows | Leave a Comment »

Stofradar – RevSpace

Posted by jpluimers on 2020/12/10

On my list to play around with: [WayBack] Stofradar – RevSpace.

It gets data from [WayBack] luftdaten.info – Feinstaub selber messen – Open Data und Citizen Science aus Stuttgart , then visualises it.

Via: [WayBack] Helga van Leur on Twitter: “Deze animatie van de uitstoot fijnstof tijdens jaarwisseling is ook treffend… Opvallend is hotspot Veghel e.o. en op Veluwe. Bron: …”

—jeroen

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

Delphi TRegExOption: Where is description of roNotEmpty option? What does this option do? – Jacek Laskowski – Google+

Posted by jpluimers on 2020/12/10

I really dislike using regular expressions, mainly because every time I bump into code using them either:

  • I cannot decipher them any more
  • It is used for things not suites for (like parsing JSON or XML: please don’t!)

For more background on when NOT to use regular expressions, remember they describe a regular grammar, and can only me implemented by a finite state machine (a state machine that can be exactly one state out of a set of finite states).

As soon as you need to parse something that needs multiple states at once, or the number of states becomes infinite,

Some background reading:

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

How To Write Unmaintainable Code: Ensure a job for life ;-) by Roedy Green Canadian Mind Products

Posted by jpluimers on 2020/12/09

A great reference on how not to code still is

How To Write Unmaintainable Code

Ensure a job for life ;-)

Roedy Green Canadian Mind Products

I am still amazed when browsing through code, how many people use one or more of the anti-patterns in it.

One example I came across was this piece of Delphi RTL code:

class function TMarshalUnmarshalBase.ComposeKey(clazz: TClass; Field: string): string;
begin
  if clazz <> nil then
    Result := clazz.UnitName + SEP_DOT + clazz.ClassName + SEP_DOT + Field
  else
    Result := '';
end;

So I did a quick search at in the Delphi RTL for clazz, then found these occurences, indicating not only the authors of them have been under a rock, but also the code reviewers:

  • 98 in data\dbx\Data.DBXJSONReflect.pas
  • 7 in data\dbx\Data.DBXTransport.pas
  • 97 in data\rest\REST.JsonReflect.pas
  • 3 in DUnit\src\TestFramework.pas
  • 22 in indy\abstraction\IPPeerAPI.pas

I have seen similar things in many environments, even run-time libraries of others, though this is one of the worst examples and falls under the anti-pattern:

Thesaurus Surrogatisation

To break the boredom, use a thesaurus to look up as much alternate vocabulary as possible to refer to the same action, e.g. display, show, present. Vaguely hint there is some subtle difference, where none exists. However, if there are two similar functions that have a crucial difference, always use the same word in describing both functions (e.g. print to mean “write to a file”, “put ink on paper” and “display on the screen”). Under no circumstances, succumb to demands to write a glossary with the special purpose project vocabulary unambiguously defined. Doing so would be an unprofessional breach of the structured design principle of information hiding.

There is a great other anti-pattern in the document too:

Delphi/Pascal Only

: Don’t use functions and procedures. Use the label/goto statements then jump around a lot inside your code using this. It’ll drive ’em mad trying to trace through this. Another idea, is just to use this for the hang of it and scramble your code up jumping to and fro in some haphazard fashion.

Enjoy reading the anti-pattern descriptions, which are now maintained at [WayBack] GitHub – Droogans/unmaintainable-code: A more maintainable, easier to share version of the infamous http://mindprod.com/jgloss/unmain.html, as it was originally a multi-page hard to maintain set of small articles:

A lot of comments were posted because of it: [WayBack] Responses to Roedy’s Unmaintainable Code Essay

Via:

–jeroen

Posted in .NET, Delphi, Development, Software Development | 1 Comment »

GitHub – DevExpress/testcafe: A Node.js tool to automate end-to-end web testing.

Posted by jpluimers on 2020/12/09

In my list of things to play with: [WayBack] GitHub – DevExpress/testcafe: A Node.js tool to automate end-to-end web testing.:

A Node.js tool to automate end-to-end web testing.
Write tests in JS or TypeScript, run them and view results.

https://devexpress.github.io/testcafe

  • Works on all popular environments: TestCafe runs on Windows, MacOS, and Linux. It supports desktop, mobile, remote and cloud browsers (UI or headless).
  • 1 minute to set up: You do not need WebDriver or any other testing software. Install TestCafe with one command, and you are ready to test: npm install -g testcafe
  • Free and open source: TestCafe is free to use under the MIT license. Plugins provide custom reports, integration with other tools, launching tests from IDE, etc. You can use the plugins made by the GitHub community or make your own.

Related:

  • [WayBack] A node.js tool to automate end-to-end web testing | TestCafe:

    Use TestCafe to write tests in JS or TypeScript, run them and view results. TestCafe runs on Windows, MacOS, and Linux and takes 1 minute to set up.

  • [WayBack] TestCafe: Web Testing Framework | DevExpress

    100% web-based functional testing framework with integrated visual test recorder, remote device testing, and natural JavaScript API

    • From download to recording your first test in less than 5 minutes — installer automatically configures your environment.
    • With TestCafe, you can run tests in any browser that supports HTML5 (including IE9+, Chrome, Firefox, Safari, Opera).
    • TestCafe is operating system agnostic so you can run tests on Windows, Mac or Linux machines.
    • Run tests on remote computers and mobile devices.
    • Run tests in multiple browsers and on multiple machines in parallel.
    • Run tests in the background on any machine.
    • TestCafe allows you to test web pages that require Basic and Windows HTTP Authentication.

Via:

Screen materials below the fold.

–jeroen

Read the rest of this entry »

Posted in Development, JavaScript/ECMAScript, LifeHacker, Power User, Scripting, Software Development, Testing, Web Development | Leave a Comment »

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