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2013, Thursday September 19

FreePascal Lazarus and Android Native Controls

We all know that the first Delphi for Android was just released...

I just found out an amazing alternative, using native Android controls, and FPC/Lazarus as compiler and IDE.

It creates small .apk file: only 180 KB, from my tests!

It makes use of direct LCL access of Android native controls, so it is a great sample.

Continue reading...

2013, Wednesday July 24

Tempering Garbage Collection

I'm currently fighting against out of memory errors on an heavy-loaded Java server.

If only it had been implemented in Delphi and mORMot!
But at this time, the mORMot was still in its burrow. :)
Copy-On-Write and a good heap manager can do wonders of stability.

Here are some thoughts about Garbage Collector, and how to temper their limitations.
They may apply to both the JVM and the .Net runtime, by the way.

Continue reading...

2013, Tuesday May 21

Performance issue in NextGen ARC model

Apart from being very slow during compilation, the Delphi NextGen compiler introduced a new memory model, named ARC.

We already spoke about ARC years ago, so please refer to our corresponding blog article for further information, especially about how Apple did introduce ARC to iOS instead of the Garbage Collector model.

About how ARC is to be used in the NextGen compiler, take a look at Marco's blog article, and its linked resources.

But the ARC model, as implemented by Embarcadero, has at least one huge performance issue, in the way weak references, and zeroing weak pointers have been implemented.
I do not speak about the general slow down introduced during every class/record initialization/finalization, which is noticeable, but not a big concern.

If you look at XE4 internals, you will discover a disappointing global lock introduced in the RTL.

Continue reading...

2013, Sunday May 19

"The shorter code, the better?"

One quick Sunday post, from a comment I wrote in a blog article.

I'm always wondering why a lot of programmers tend to implicitly assume that "the shorter source code, the better".

It is true when it means that with proper code refactoring, making small objects with dedicated methods, the code of your methods will be smaller.
It is true when you do not like to write as a "Copy & Paste" coder, without searching to put common code in shared places.

But is it true at the language level?
I mean, is it just because your ARC or GC model allow you not to manage the object memory, that it is always better?

Just some ideas...

Continue reading...

2013, Saturday May 11

Delphi XE4 NextGen compiler: using byte instead of ansichar?

When I first read the technical white paper covering all of the language changes in XE4 for mobile development (tied to the new ARM LLVM-based Delphi compiler), I have to confess I was pretty much confused.

Two great mORMot users just asked for XE4/iOS support of mORMot.

Win32/Win64 support for XE4 will be done as soon as we got a copy of it.
I suspect the code already works, since it was working as expected with XE3, and we rely on our own set of low-level functions for most internal work.

But iOS-targetting is more complex, due to the NextGen compiler, mainly.

Continue reading...

2013, Monday April 22

TDataSet... now I'm confused

You perhaps know that I'm not a big fan of the TDataSet / RAD DB approach for end-user applications.
They are easy to define, almost no code to write, and you are able to publish a working solution very fast.

But it is a nightmare to debug and maintain. I prefer the new DataBinding feature, or... of course... ORM!
In mORMot, we have some auto-generated screens, and in our roadmap, we forcast to use some auto-binding features, using a KISS by-convention MVC pattern.

For some users, we made a ORM / TDataSet conversion unit.
And we discovered that TDataSet has a weird, and very misleading definition of its AsString property, for Unicode versions of Delphi.

Continue reading...

2013, Tuesday March 26

Delphi is just a perfect fit for the average programmer

On the Embarcadero forums, some user did have a perfectly sane reaction, about a non obvious integer type cast like Int64Var := Int32Var*Int32Var, which may overflow.

We've got to stop becoming, as one poster put it, "human pre-compilers" for Delphi.
The compiler ought to have the common sense to not need the programmer to cast the two integer values.

I respectfully think just the opposite.
;)

Such a type cast is part of the language grammar.
If you know the grammar, you will know how it will be compiled.

To be honest, you have the same in all languages, with more or less range checking, optimization, and implicit conversion.
This is why I like Delphi: it can be mastered by any programmers, whereas truly mastering Java or .Net needs a genius.


Delphi is just... human...

Continue reading...

2013, Wednesday March 13

x64 optimized asm of FillChar() and Move() for Win64

We have included x64 optimized asm of FillChar() and Move() for Win64 - for corresponding compiler targets, i.e. Delphi XE2 and XE3.
It will handle properly cache prefetch and appropriate SSE2 move instructions

The System.pas unit of Delphi RTL will be patched at startup, unless the NOX64PATCHRTL conditional is defined.
Therefore, whole application may benefit for this optimized version.

Performance improvement is noticeable, when compared with the original pascal-based version included in System.pas.

By the way, the Delphi x64 built-in assembler does not recognize the movnti opcode... so we had to inline it as plain db hexadecimal values.
A bit disappointing. Until now, we did not suffer from anything in regard to the x64 compatibility at Delphi level.

No stand-alone unit available yet, since it is included in our SynCommons.pas shared unit, starting with the 1.18 revision of mORMot.

Feedback is welcome, as usual!

2012, Thursday December 20

How to make it fast?

On our forum, a clever question was posted about publishing some enhanced RTL functions for newer versions of Delphi - as we did for Delphi 7 and 2007.

I was looking for a faster IntToStr implementation and discovered SynCommons.pas.
(....)
That's really too bad, SynCommons.pas really does contain some seriously fast stuff, people would greatly benefit from it if it was made general-purpose.

In fact, it would not be enough to change the RTL function implementations.
IMHO, to write something scalable, you need to get rid of such functions.

Continue reading...

2012, Tuesday November 13

Go language and Delphi

Do you know the Go language?

It is a strong-typed, compiled, cross-platform, and concurrent.
It features some nice high-level structures, like maps and strings, and still have very low-level access to the generated code: pointers are there, in a safe strong-typed implementation just like in pascal, and there is even a "goto", which sounds like an heresy to dogmatic coders, but does make sense to me, at least when you want to optimize code speed, in some rare cases.

It is created/pushed by Google, used internally by the company in their computer farms, and was designed by one of the original C creators.

Continue reading...

2012, Thursday October 18

Interfaces are not evil; or are Delphi-ers the new Vampires?

A very interesting comment by mpv in our forum highlighted some points about potential interface (ab)use:

IMHO: Idea is good, but "the devil is in the details". To use mocking I must use interfaces. When I use interfaces I lost control on code, because I don't see implementation. Debugging an optimization became very hard. Especially if a beginner developer read something like GOF (Gang Of Four) and wherever necessary and where not use design templates like Visitor, Decorator and so on, and in debugging I don't understand at all what class actually implement passed interface. As for me, this is a biggest problem for .NET framework - developers use interfaces, don't look on implementation (and often don't have it in sources at all), do not learn by reading someone else's code and therefore produce monkey-code. This is only IMHO...

Could sounds rude, and like a trolling subject, but I perfectly understand this point of view.
Introducing stubs and mocks in mORMot was not the open door to all problems.. but,on the contrary, to help write robust, efficient, and maintainable code.
It does not mean that using interfaces and C#/Java is the root of all evils and code inefficiency, but that it may lead into problems.

Continue reading...

2012, Saturday October 6

Delphi XE3 is preparing (weak) reference counting for class instances

In Delphi, you have several ways of handling data life time, therefore several ways of handling memory:

  • For simple value objects (e.g.  byte integer double shortstring and fixed size arrays or record containing only such types), the value is copied in fixed-size buffers;
  • For more complex value objets (e.g. string and dynamic arrays or record containing such types), there is a reference counter handled by each instance, with copy-on-write feature and compiler-generated reference counting at code scope level (with hidden try..finally blocks);
  • For most class instances (e.g. deriving from TObject), you have to Create then Free each instance, and manage its life time by hand - with explicit try..finally blocks;
  • For class deriving from TInterfacedObject, you have a RefCount property, with _AddRef _Release methods (this is the reference-counted COM model), and you can use Delphi interface to work with such instances - see this blog article.
With Delphi XE3, we were told that some automatic memory handling at class level are about to be introduced at the compiler and RTL level.
Even if this feature is not finished, and disabled, there are a lot of changes in the Delphi XE3 Run Time Library which sounds like a preparation of such a new feature.

Continue reading...

2012, Thursday August 30

WinRT support for XE3

Apart the sad and concerning license change issue (which has been confirmed by David I. himself), XE3 has some features, in order to support Windows 8 new 'tile-based' interface (formerly known as "Metro").

Windows Runtime, or WinRT (not to be confused with Windows RT, which is a tablet manufacturer only version of Windows 8) is a cross-platform application architecture on the Windows 8 operating system.
WinRT supports development in C++/CX (Component Extensions, a language based on C++) and the managed languages C# and VB.NET, as well as JavaScript.
WinRT applications natively support both the x86 and ARM architectures, and also run inside a sandboxed environment to allow for greater security and stability.
WinRT will also be part of the upcoming Windows Phone 8 operating systems.
(source: Wikipedia)

It has been clearly stated that only Microsoft compilers and runtime libraries (RTL) will be able to have full access to the low-level API needed to create a decent RTL.
This has been done for security reasons, but it won't allow third-party JIT or compilers to work as expected. Only Microsoft's C++ and C# compilers / virtual machines have access to the needed API. Even if you do not have a JIT in your language (Delphi is compiled and do not have any virtual machine), you would need to access to some low-level API calls e.g. to mark some memory block as executable (e.g. for virtual methods stubbing).

So Delphi is not able to have native support of WinRT, due to this limitation.

This is a known fact, but let us tell about "Windows 8 sideloading" feature, available with XE3.
In short, even if you do not have 100% WinRT application, XE3 "Metropolis" (sic) styled Desktop applications have some potential to behave like native UI applications, even if not being native.

Continue reading...

2012, Tuesday August 28

"Trop c'est trop" - No Client-Server for XE3 PRO users

Here is some unbelievable news retrieved from "Te Waka o Delphi" blog:

From XE3 onwards, your Delphi Professional EULA will prohibit you from using Delphi Professional for anything other than local data access.
If you want to build client/server database applications using Delphi Professional, you will be required to purchase a “Client/Server Add-On” pack.

This goes beyond the fact that you do not get (or can otherwise use or install) client/server drivers for the DBExpress or other “built in” data access frameworks, but extends even to 3rd party data access technologies.
That is, whatever you may be able to do or achieve – technically – using some 3rd party component or library with you Delphi Professional compiler, you cannot legally create a client/server application.
Never mind any 3rd party components or libraries, this same prohibition will apply even if you are using naked, unadorned Microsoft ADO.

Damn show-stopper for me.
Embarcadero is killing Delphi.

Our very own mORMot Open-Source framework is fully Client-Server oriented, and allow creating scalable Client-Server applications even with an Oracle DB system back-end, even with XE2 starter edition (direct access, without any DB.pas / DBExpress layer).

Continue reading...

2012, Monday June 18

Circular reference and zeroing weak pointers

The memory allocation model of the Delphi interface type uses some kind of Automatic Reference Counting (ARC). In order to avoid memory and resource leaks and potential random errors in the applications (aka the terrible EAccessViolation exception on customer side) when using interface, a SOA framework like mORMot has to offer so-called Weak pointers and Zeroing Weak pointers features.

Note that garbage collector based languages (like Java or C#) do not suffer from this problem, since the circular references are handled by their memory model: objects lifetime are maintained globally by the memory manager. Of course, it will increase memory use, slowdown the process due to additional actions during allocation and assignments (all objects and their references have to be maintained in internal lists), and may slow down the application when garbage collector enters in action. In order to avoid such issues when performance matters, experts tend to pre-allocate and re-use objects: this is one common limitation of this memory model, and why Delphi is still a good candidate (like unmanaged C or C++ - and also Objective C) when it deals with performance and stability.

Continue reading...

2012, Wednesday June 13

Retrieve the object instance from an interface

It is pretty useful, in some cases, to retrieve a class instance from a given interface.
You should better use interfaces in your business logic, but having access to the underlying implementation is needed at lower level.

Beginning with Delphi 2010, you are able to use the as operator, e.g. via aObject := aInterface as TObject or aObject  := TObject(aInterface).
This operator use a special hidden interface GUID (ObjCastGUID) to retrieve the object instance, calling an enhanced version of TObject.GetInterface.

But if you want to maintain compatibility with older version of Delphi (as we want for mORMot to work with the beloved Delphi 6 or 7), you'll have to find a way.

Continue reading...

2012, Monday May 28

Is marketing the new native?

In a very nice (like always) blog post, trolling comments were dispatched about the "native" concept:

From the technical point of view, both assertions are false.

The article was subtitled: "Say a Lie Often Enough and You’ll Start Believing it Yourself".
At least, it is a trolling subject.

It remembered me about some of my past studies, i.e. five years of university studies in Medieval Theology in Italy and France (yes, I know, this is strange background for a Delphi programmer):

"Stat Roma pristina nomine, nomina nuda tenemus"

Our modern world is not thinking any more, it is sinking into nominalism, whereas IMHO the scientific approach is more compatible with a realistic approach of universals.

Today, marketing is everything.
Is it a necessary evil?

Continue reading...

2012, Sunday May 20

Recursive calls and private objects

In a Stack Overflow question, someone asked about some nested procedure call he found out. That is, a procedure inside another procedure.

He found out this coding style to be messy, which sounds like a reasonable opinion. But his alternative proposal of putting the internal procedure outside the main one, i.e. making it global, is IMHO even worse.

In some case, a private class, or even record or object with methods is an handy and maintainable implementation pattern.

Continue reading...

2012, Thursday April 19

Smart: mORMot, from Delphi to JavaScript

Did you hear from the great Smart project?

It is an IDE and some source runtime able to develop and compile an Object-Pascal project into a HTML 5 / CSS 3 / JavaScript embedded application.
It does target AJAX Mobile application creation (i.e. Android and iPhone/iPad apps running Web-Kit).
You'll get an unique .html file containing the whole client-side application: it won't need any server side implementation. Using a third-party tool like PhoneGap, you'd be able to supply your customers with true native applications, running without any network, and accessing the full power of any modern Smart Phone.

Smart is a great candidate for implementing rich client-side AJAX applications, to work with our client-server mORMot framework.

In order to interface Smart code with mORMot, we started implementing some low-level code to work with our RESTful authentication scheme.

So we'll need to implement some Smart dedicated Open Source code implementing crc32 and SHA-256 hashing.

Continue reading...

2012, Tuesday April 10

How function results are allocated

One potential issue with Delphi coding, is about how the result of a functions are implemented.

If you forget to set a result value to a function, you'll get a compiler warning.
Never underestimate such warning: IMHO this is not a warning, but an error.

And you should better be aware of the handling of reference-counted types (e.g. string) in a function results: those are passed the stack as var parameters, so the result of a function may be set even if an exception is raised during function execution!

Continue reading...

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