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 ‘Conferences’ Category

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The Delphi System.Exit “Function”

Posted by jpluimers on 2019/10/17

Still wrongly documented as System.Exit Function [WayBack], most people think it is a statement.

However, it is a compiler intrinsic procedure in the System unit that – when called inside a real function – optionally accepts a parameter with the same type as the encompassing function because it is a compiler intrinsic. It kind of acts as an overloaded procedure, but in fact translate to machine code via an intermediate parse tree.

The parameterless version has been there since at least Turbo Pascal 3.0, but the parameterised version is more recent: I think it was introduced around Delphi 7.

It then stops executing that function after first executing any explicit or implicit finally blocks.

I’ve seen various projects that used their own Exit procedure. This is a very bad habit: Since the System unit is always further away in scope, the introduced one is called which can severely confuse programmers not being aware of this.

The code generation for the parameterless and parameterised  “overloads” of System.Exit is slightly different:

  • The parameterless one can often be optimised away, for instance folding multiple calls to them into one, or rearranging code execution so a jump isn’t needed any more. This means you cannot always put a breakpoint on them.
  • The parameterised one always needs code to load the function result, so you can always put a breakpoint on them.

Stefan Glienke explained the above in [WayBack] The advantage of using Exit() instead of a plain Exit? You can place a breakpoint! – Uwe Raabe – Google+

–jeroen

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

How to debug small programs

Posted by jpluimers on 2019/10/17

As a follow up of SSCCE, MWE and MCVE are basically the same: provide code people can use to reproduce a problem, I found [WayBack] How to debug small programs which is starts as

One of the most frequent categories of bad questions I see on StackOverflow is: I wrote this program for my assignment and it doesn’t work. [20 lines of code]. And… that’s it.

Then it goes on how to debug those pieces of code, trim them into an SSCCE/MWE/MCVW to form the base of a question which you can ask on StackOverflow/SuperUser/ServerFault/StackExchange, forum, group/community or even your co-worker.

The really cool thing about the techniques used there are that they also apply to bigger pieces of code, heck even large code bases.

They force you to trim down your problem in to manageable pieces that are easy to explain and write concise documentation and tests around them to assist you in the process.

Below are the steps in a short list. Be sure to read the original article How to debug small programs | Fabulous adventures in coding after going through the list.

  1. Turn on compiler warnings, inspect all of them, resolve or explain them
  2. Rubber duck to an imaginary person or even a live one explaining each part in simple terms
  3. If the bug is still there, break up the code into pieces
  4. Write technical specifications for all the pieces
  5. Verify the pieces against the specifications, for instance by adding pre- and postconditions to them
  6. Add assertions in the pieces for all the specifications
  7. Write test cases for the pieces
  8. Write down on paper the expected behaviour for all the lines of code
  9. Use a debugger to step through all the lines of code and verify the expected behaviour you wrote down
  10. While debugging, listen to all your doubts (gut feeling is a good thing!)

This sounds like a lot of work. It is. All good programming is.

If you apply these before writing any logic code, then your life becomes easier because you will spot bugs sooner:

  • specification
  • test cases
  • preconditions
  • postconditions
  • assertions

Does this again sound like a lot of work?

Then remember: taking a shortcut will make the actual work longer. The reason is that hunting for bugs is a tedious and time consuming process scaling very badly with complexity.

–jeroen

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

SSCCE, MWE and MCVE are basically the same: provide code people can use to reproduce a problem

Posted by jpluimers on 2019/10/16

Many times I see people asking questions about problems in their source code, it goes like this:

  1. Question is asked formulating the problem, but without any source code
  2. A comment asks for source code
  3. Either the response is “the source code is too big”, or the response contains a really big blob of (compressed) code that

If you have such questions (I still often have them), then you need to do just two things (which you often can combine in one step):

  1. Condense down the code into a small bit that others can use to reproduce the problem.
  2. Talk to an (imaginary) person explaining the problem you have and the condensed code.

The second is called Rubber Ducking after a story in the book The Pragmatic Programmer in which a programmer would carry around a rubber duck.

The first is known under at least three terms:

They all come down to the following:

Provide a small piece of working code that is readable anyone can use to reproduce a problem without much effort.

via: Can we create a Help Center topic that outlines what a SSCCE / MWE means for Stack Overflow?

–jeroen

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

Sprints, marathons and root canals and Brady Printed Lean Labels – for lean development

Posted by jpluimers on 2019/10/15

Apart from blank and custom labels, Brady also sells [WayBack] Brady Printed Lean Labels | BradyID.com

They work great for agile projects, despite marketed as “will help you improve reliability, up-time, and efficiency”.

I found them via:

 

which led me to [WayBack] Sprints, marathons and root canals, which is a long but recommended read.

That got me to a book that is now on my reading list: [WayBack] James Shore: Agile-Book, especially this chapter:

[WayBack] James Shore: The Art of Agile Development: Iteration Planning

 

Assorted sets of stickers are (all in packs of 10 each):

[WayBack] Brady Part: 110762 | Assorted Lean Stickers

[WayBack] Brady Part: 110763 | Assorted Reliability Stickers

 

Though you can also get them individually in 10 packs:

Read the rest of this entry »

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

Great video “Why Functional Programming Matters”, by Ted Neward on getting started with Functional Programming

Posted by jpluimers on 2019/10/10

Great introduction into functional programming by a step by step: “Why Functional Programming Matters”, by Ted Neward on Devoxx Poland 2016.

It uses Java, but translates very well into C#, C++, Delphi and many other programming languages because the underlying support structures are very easy (a ~50 line Lists class, a few Function# prototypes, etc).

Two great observations here:

  • most variables don’t vary
  • collections are the gateway drug to becoming functional programmers

Summary

Coding Tech

In the latter half of the 2000s, a new kind of programming language seemed poised to take the steam out of the dominancen of object-oriented programming languages and their hold over “mainstream” development. But these new languages, collectively referred to as “functional” languages, were nothing new. In fact, they’ve been a part of the language landscape since the late 80s, and arguably even longer than that. What makes a functional language, and what makes a functional language interesting? Most importantly, why do we care now, thirty years after their introduction?

https://www.youtube.com/watch?v=oB8jN68KGcU

–jeroen

Read the rest of this entry »

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

“Use TXSxxxx classes for simple nillable types”

Posted by jpluimers on 2019/10/08

For my link archive:

The first one missed these:

Both find these:

–jeroen

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

Delphi; on my research list `Error creating form: Root class not found: “”.`

Posted by jpluimers on 2019/10/03

On my Delphi research list:

[Window Title]
Error

[Content]
Error creating form: Root class not found: "".

[OK]

I think it has to do with form inheritance, but a quick glance didn’t raise any warning signs.

–jeroen

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

Terminate threads during application or not?

Posted by jpluimers on 2019/10/02

I got an interesting question a while ago: should an application terminate (anonymous) threads or not?

A problem is that a thread might not execute unless you call WaitFor before Terminate is called. The reason is that the internal function ThreadProc does not start Execute if the thread is already terminated.

The ThreadProc in the System.Classes unit is an ideal place to set breakpoints in order to see which threads might start.

Other useful places to set breakpoints:

  • TAnonymousThread.Execute
  • TExternalThread.Execute

Execute not being called by ThreadProc is a bug, but it is not documented because QC is gone (taking the below entry with it), it is not in QP and the docwiki never got updated.

Given QC has so much information, I am still baffled that Embarcadero took it down.

Sergey Kasandrov (a.k.a. serg or sergworks) wrote in [WayBack] Sleep sort and TThread corner case | The Programming Works about this bug and refers to WayBack: QualityCentral 35451 – TThread implementation doesn’t guarantee that thread’s Execute method will be called at all .

The really bad thing are the WayBack: QualityCentral Resolution Entries for Report #35451 Resolution “As Designed” implying the design is wrong.

In his post, sergworks implemented the Sleep sorting in Delphi. Related:

Note that application shutdown is a much debated topic. Best is to do as little cleanup as possible: your process is going to terminate soon anyway. No need to close handles or free memory: Windows will do that for you anyway. See for instance:

 

Related to waiting:

Related to executing:

–jeroen

Posted in Conference Topics, Conferences, Delphi, Development, Event, Multi-Threading / Concurrency, Software Development, The Old New Thing, Windows Development | Leave a Comment »

Soap Delphi Client end with a timeout for a 1MB call – Stack Overflow

Posted by jpluimers on 2019/09/26

This was a change between IE6 and IE7 on the default time-out decreasing from 3600 seconds to 30 seconds: [WayBack] Soap Delphi Client end with a timeout for a 1MB call – Stack Overflow.

If you want to increase the timeout, then use InternetSetOption. You can get the current value using InternetQueryOption.

In Delphi, THTTPReqResp.Send supports this by setting the various time out options right after creating the request:

    Request := HttpOpenRequest(FInetConnect, 'POST', PChar(FURLSite), nil,
                               nil, nil, Flags, 0{Integer(Self)});
    Check(not Assigned(Request));

    { Timeouts }
    if FConnectTimeout > 0 then
      Check(not InternetSetOption(Request, INTERNET_OPTION_CONNECT_TIMEOUT, Pointer(@FConnectTimeout), SizeOf(FConnectTimeout)));
    if FSendTimeout > 0 then
      Check(not InternetSetOption(Request, INTERNET_OPTION_SEND_TIMEOUT, Pointer(@FSendTimeout), SizeOf(FSendTimeout)));
    if FReceiveTimeout > 0 then
      Check(not InternetSetOption(Request, INTERNET_OPTION_RECEIVE_TIMEOUT, Pointer(@FReceiveTimeout), SizeOf(FReceiveTimeout)));

Related:

–jeroen

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

How to expose a Delphi set type via Soap – Stack Overflow

Posted by jpluimers on 2019/09/25

Marjan Venema had a great answer at [WayBack] How to expose a Delphi set type via Soap – Stack Overflow.

–jeroen

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

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