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

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Archive for December, 2020

OutputDebugStringA limitation used to be close to 4K, but with OutputDebugStringW, what is the limitation?

Posted by jpluimers on 2020/12/31

I wonder what the limitation of OutputDebugStringW is, as OutputDebugStringA had a limit imposed by the DBWIN_BUFFER which was 4K (minus a bit overhead):

–jeroen

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

Syncing your fork to the original repository via the browser · KirstieJane/STEMMRoleModels Wiki · GitHub

Posted by jpluimers on 2020/12/31

[WayBack] Syncing your fork to the original repository via the browser · KirstieJane/STEMMRoleModels Wiki · GitHub

TL;DR: you can do the sync from the Web UI, but it always gives you an extra merge commit.

–jeroen

Posted in Development, DVCS - Distributed Version Control, git, GitHub, LifeHacker, Power User, Source Code Management | Leave a Comment »

It pays to closely look to your coding

Posted by jpluimers on 2020/12/31

I like questions like [WayBack] How to check if parent menu item has “checked” child item? – VCL – Delphi-PRAXiS [en]

It means that the asker is closely looking at her or his coding.

This is important, as it helps to get your programming idioms consistent.

The code started out as:

function HasCheckedSubItems(AMenuItem: TMenuItem): Boolean;
var
  i: integer;
begin
  Result := False;
  for i := 0 to AMenuItem.Count - 1 do
    if AMenuItem.Items[i].Checked then
      Exit(True);
end;

and finally ended up as:

function HasCheckedSubItems(AMenuItem: TMenuItem): Boolean;
var
  I: integer;
begin
  for I := 0 to AMenuItem.Count - 1 do
    if AMenuItem.Items[I].Checked then
      Exit(True);
  Exit(False); 
end;

Which is close to what I’d use, no matter the Delphi version:

function HasCheckedSubItems(const AMenuItem: TMenuItem): Boolean;
var
  I: integer;
begin
  for I := 0 to AMenuItem.Count - 1 do
    if AMenuItem.Items[I].Checked then
    begin
      Result := True;
      Exit;
    end;
  Result := False;
end;

My argumentation for the last form is that assignment and jumps are too conceptually different to combine in one statement.

The second form moves just one assignment, which on the current scale of nanosecond execution might not sound much, but conceptually limits the assignment to once per function call.

If you are interested in more thoughts on this topic,

  1. read How to Design Early Returns in C++ (Based on Procedural Programming) – Fluent C++
  2. watch Procedural Programming: It’s Back? It Never Went Away – Kevlin Henney [ACCU 2018] – YouTube
  3. save the slides from [WayBack

–jeroen

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

A garbage collector for C and C++ (and a wrapper for Delphi): The Boehm-Demers-Weiser conservative C/C++ Garbage Collector

Posted by jpluimers on 2020/12/30

I bumped into [WayBackA garbage collector for C and C++ a while ago, for which the source is at [WayBack] GitHub – ivmai/bdwgc: The Boehm-Demers-Weiser conservative C/C++ Garbage Collector (libgc, bdwgc, boehm-gc).

There is a (very old!) wrapper for Delphi too: [WayBack] 21646 API for Boehm Garbage Collector DLL

Barry Kelly <barry_j_kelly@hotmail.com>,
19 April 2004
——————————————————
This archive contains a simple API unit for the Boehm Garbage Collector DLL, along with another unit which makes it easier to use with classes, and a demonstration application. Also included is the Boehm GC DLL binary, along with source code in the gc_dll_src directory.

The files:

BoehmGc.pas
———–
This unit exports a dozen or so routines from the Boehm GC dll. Since the GC integrates with and replaces the Delphi default memory manager, you probably don’t need to use this unit unless you want to fine-tune the behaviour of the DLL. The DLL exports more routines than are in this unit; the C prototypes are in the gc_dll_src/gc.h header file, and can be imported as needed. If you allocate large chunks of memory (>100K) which don’t contain references to other chunks (and thus don’t need to be scanned for pointers), there are routines in this unit which you can use to increase performance.

General advice: don’t tweak until you need to tweak.

Gc.pas
——
This is the main unit. Put this unit first in the uses clause of you project and the project will automatically use garbage collection. If you want to use objects which require finalization and you don’t want to have to call TObject.Free / TObject.Destroy on them manually, you can use the MarkForFinalization(TObject) function. The basic pattern is to register the object for finalization in its constructor and unregister it with UnmarkForFinalization in its destructor. This handles the two most common use cases for finalization: GC-invoked finalization and manual finalization. Note that it’s always safe to behave as if GC doesn’t exist, and use GetMem/FreeMem, New/Dispose, Create/Free etc. The use of these units simply allows you to also program with garbage collection.

GcTest.dpr & GcTest.exe
———————–
This program contains simple sample code demonstrating the garbage collector in action.

BoehmGC.dll
———–
This contains the implementation of the garbage collector itself. The DLL can be recompiled from the source in gc_dll_src with various options, including multithreaded support, different pointer alignment granularities, etc.

****
The original Boehm GC source comes from: http://www.hpl.hp.com/personal/Hans_Boehm/gc/

I’m Barry Kelly: barry_j_kelly@hotmail.com

You can do anything you like with my source code (*.pas, *.dpr).

See the file gc_dll_src/LICENSEa for permissions for the GC itself.

</barry_j_kelly@hotmail.com>

Although when trying to download, I got this for both cc.embarcadero.com/Download.aspx?id=21646 and cc.embarcadero.com/Download.aspx?id=21646&prot=ftp:

Access to the path ‘\\etnaedndb02.embarcadero.com\f\webcache\cc\2004\4\19\21646.zip’ is denied.

An error has occurred while processing the page.

Please try to refresh the page, or return to the home page.

: ETNACDC04

and [WayBackJeroen Pluimers auf Twitter: “It looks like the @EmbarcaderoTech code central file cc.embarcadero.com/Item/21646 is broken: “Access to the path ‘\https://t.co/3f3blXN9mp\f\webcache\cc\2004\4\19\https://t.co/0UJUtWvxVV’ is denied.” when exploring or downloading.…”

 Explore the files in this upload

File Exploration is Disabled

We’re sorry, but errors in the uploaded zip file prevent it from being explored.

The error generated by the Zip attachment is:

Access to the path ‘\\etnaedndb02.embarcadero.com\f\webcache\cc\2004\4\19\21646.zip’ is denied.You may still be able to repair the zip file contents if you download the entire zip locally. You may also want to ask the author to repost the attachment.

Via [WayBack] delphi – Reference-counting for objects – Stack Overflow which also points to:

Downloads of stable versions: [WayBack] Download · ivmai/bdwgc Wiki · GitHub

–jeroen

Read the rest of this entry »

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

Windows command prompt: decrementing loop

Posted by jpluimers on 2020/12/30

I needed a decrementing loop on the Windows command prompt, but that seems very hard from batch files without programming your own kind of while loop:

PowerShell to the rescue to loop back from and including 463 down to and including 290:

PowerShell -Command "for ($i=463; $i -ge 290; $i--) { Write-Host "Value " $i}"

This outputs:

Value 463
Value 462
...
Value 291
Value 290

In a similar way, you can execute a cmd command, but then you need to be careful on how to pass parameters: the \" is important to you can have quotes within quoted strings..

PowerShell -Command "for ($i=463; $i -ge 290; $i--) { & echo \"Value $i\"}"

gives this:

Value 463
Value 462
...
Value 291
Value 290

Read the rest of this entry »

Posted in Batch-Files, CommandLine, Console (command prompt window), Development, PowerShell, PowerShell, Scripting, Software Development, Windows | 1 Comment »

 
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