Re: [fpc-other] What makes a Compiler project (like FPC) special?

[Sven Barth via fpc-other]

2017-05-25 21:29 GMT+02:00 Graeme Geldenhuys :
> On 2017-05-25 19:47, Nikolay Nikolov wrote:
> So what is Florian going on about regarding workflow and Git not being able
> to cope in a "compiler" based project? He made it out as if FPC will not be
> workable in a Git managed environment. I don't see his analogy. The Linux
> Kernel running on more platforms than FPC does, is just as complex a beast,
> if not more - considering that the Linux Kernel probably has 10's of
> millions of lines of code, 2000+ contributors. The same could be said for
> the KDE and Qt framework. The latter runs on just about every platform out
> there, as multiple rendering engines, font engines, theme engines, layout
> engines etc.

The workflow of the Linux kernel would simply not be acceptable for us
with them having this hierarchy of maintainers with Linus at the top
and doing all the final merging. If at all an approach like Qt uses
with automatic continous integration of pull requests committed by
core devs or forwarded by them from non-core devs would be the way to
go for us - if at all.

Regards,
Sven
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Re: [fpc-other] Felipe: Java and multi-threading

[Graeme Geldenhuys]

Hi Felipe,

> This simple program never ends if you delete the volatile keyword (I
> tested here in Windows):

Yes, I got the same behaviour as you, using Java 1.8 under FreeBSD. But 
I immediately saw your problem. You are accessing the same data from 
more than one thread. That has always been a big NO-NO in any 
programming language.


Using the synchronized code blocks to protect the common data or actions 
being executed I get this as output.


[threads]$ java FelipeTestThread
Thread 2 finishing
Thread 1 finished. Counted up to 2205390
[threads]$

It works, just like it does when the "volatile" keyword is used.

Attached is the corrected version of your sample application without the 
volatile keyword. It is worth noting that using volatile is faster, but 
also has its limits (ie: you can't protect a whole block of code or 
actions).


But the bottom line is, you tried to access common data from multiple 
threads, without trying to protect that data. Not the way to go!


Regards,
  Graeme

--
fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal
http://fpgui.sourceforge.net/

My public PGP key:  http://tinyurl.com/graeme-pgp
class FelipeTestThread {

	//volatile keyword not needed any more
	private boolean running = true;

	public void test() {
		// thread 1
		new Thread(new Runnable() {
			public void run() {
int counter = 0;
while (isRunning()) {
	counter++;
}
System.out.println("Thread 1 finished. Counted up to " + counter);
			}
		}).start();
		
		// thread 2
		new Thread(new Runnable() {
			public void run() {
// Sleep for a bit so that thread 1 has a chance to start
try
{
	Thread.sleep(100);
} catch (InterruptedException ignored) {
	// do nothing
}
System.out.println("Thread 2 finishing");
//running = false;
stopRunning();
			}
		}).start();
	}
	
	public static void main(String[] args) {
		new FelipeTestThread().test();
	}
	
	public void stopRunning() {
		synchronized(this) {
		  running = false;
		}
	}
	
	public boolean isRunning() {
		synchronized(this) {
			return (running == true);
		}
	}
}
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Re: [fpc-other] Felipe: Java and multi-threading

[Graeme Geldenhuys]

On 2017-05-26 15:56, Graeme Geldenhuys wrote:

Attached is the corrected version of your sample application without the
volatile keyword. It is worth noting that using volatile is faster, but
also has its limits (ie: you can't protect a whole block of code or
actions).


To add to this, there is also a memory access effect between volatile 
and synchronize. For a detailed explanation, take a look the marked 
"correct answer" in this StackOverflow topic:



https://stackoverflow.com/questions/3519664/difference-between-volatile-and-synchronized-in-java



Regards,
  Graeme

--
fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal
http://fpgui.sourceforge.net/

My public PGP key:  http://tinyurl.com/graeme-pgp
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Re: [fpc-other] How do you keep up with FPC discussions?

[Ralf Quint]

On 5/26/2017 4:36 AM, wkitt...@windstream.net wrote:
>
> hahaha... nope... just experienced readers of messages who have
> learned how to work through them fairly quickly and easily... i will
> grant that it does take an hour or two... if i'm offering someone some
> help and have to go write code, i do that over several days... even if
> it means skipping some reading a day or two... 
And on top of that, experienced enough to use a proper email client,
with proper message filtering, instead of (ab)using a web browser just
just another task... ;-)

Ralf

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Re: [fpc-other] How do you keep up with FPC discussions?

[noreply]

On 2017-05-26 10:27, Ralf Quint wrote:

On 5/26/2017 4:36 AM, wkitt...@windstream.net wrote:


hahaha... nope... just experienced readers of messages who have
learned how to work through them fairly quickly and easily... i will
grant that it does take an hour or two... if i'm offering someone some
help and have to go write code, i do that over several days... even if
it means skipping some reading a day or two...

And on top of that, experienced enough to use a proper email client,
with proper message filtering, instead of (ab)using a web browser just
just another task... ;-)

Ralf



Indeed I hate web based programs of all kinds, but, after lots of my 
email clients corrupted their databases which were not in plain text and 
I lost my emails, I started using web servers and web programs as email 
clients for lots of email.  Thunderbird was an option, as AFAIR you 
could store email as plain text, which is easier to recover if there is 
a failure, but thunderbird, was bloated and took up way too much memory.
Sylpheed claws was another one I was interested in, as it had one of the 
most advanced "Rule" system to automate tasks. More advanced than any I 
could find.. it has changed names to claws-mail



However, IMO it has nothing to do with filtering out email because you 
still have to read the email lists and read through emails no matter how 
much you filter things. It's not like you can magically guess that "all 
emails regarding anything to do with VARARGS I want to delete" because 2 
months later you may need varargs help. Or, it's not like you can 
magically guess that you don't want any emails coming in that have 
anything to do with fixed arrays, because you don't use fixed arrays - 
but maybe you will in 2 months!


Setting up thousands of filters is a time waster too...

But, this does bring me back to the sylpheed claws exploration days when 
I was really into automating email rules using advanced 
filtering/rulesets. I don't use them much any more but I used to use 
them like crazy

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Re: [fpc-other] How do you keep up with FPC discussions?

[noreply]

On 2017-05-25 06:10, Mark Morgan Lloyd wrote:

On 25/05/17 10:20, Graeme Geldenhuys wrote:
On 2017-05-25 09:02, Mark Morgan Lloyd wrote:> even if most of the 
time

he> pushes it far harder than many of us enjoy.
I’m afraid it’s an occupational habit. My job as a technical 
consultant

and developer often requires me to come up with more efficient ways of
doing things. Yes, inefficient ways and code really grind on me. I’ll
try my best not to push this any further here.


I /am/ trying to be neutral on this, but I think it has pretty much
been done to death here: particularly since Florian has given his
ruling.


Well if we want to come up with  an efficient way of doing things, it's 
possible that Git and SVN are both not the answer to development model. 
The answer may be to start up a campus, similar to microsoft campus, 
with multiple buildings and developers that can literally knock on each 
others door when needing assistance :-)


i.e. freepascal becomes a campus... with social eating events in the 
campus at lunch.


But that would require funding and relocating of all developers, and, 
even in a campus you'd probably still use svn/git anyway :-)

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Re: [fpc-other] How do you keep up with FPC discussions?

[Ralf Quint]

On 5/26/2017 6:25 PM, nore...@z505.com wrote:
>
> Indeed I hate web based programs of all kinds, but, after lots of my
> email clients corrupted their databases which were not in plain text
> and I lost my emails, I started using web servers and web programs as
> email clients for lots of email.  Thunderbird was an option, as AFAIR
> you could store email as plain text, which is easier to recover if
> there is a failure, but thunderbird, was bloated and took up way too
> much memory.
I am using Thunderbird, on Windows 7/8.1/10, macOS and Linux  Mint Mate
for several years now, ever since I had due to a move switch away from
my old desktop running Eudora as the email client and use a laptop
instead. And it has the benefit now that it runs on all three main OS
that I use every day.
And that is using 6 different email addresses (right now, one
specifically for ), all using IMAP for ages now. And compared to the
amount of memory you are using in a web browser to get even close to the
comforts you get with a real email client, it is rather "lean and mean"...
>
> However, IMO it has nothing to do with filtering out email because you
> still have to read the email lists and read through emails no matter
> how much you filter things. It's not like you can magically guess that
> "all emails regarding anything to do with VARARGS I want to delete"
> because 2 months later you may need varargs help. Or, it's not like
> you can magically guess that you don't want any emails coming in that
> have anything to do with fixed arrays, because you don't use fixed
> arrays - but maybe you will in 2 months!
>
Then you do not understand how you can apply filtering. You can mark
threads you are not interested in as "read on arrival", or depending on
the subject, move them in logical subfolders where you can read them as
needed. Likewise, you can mark "hot topics" with a tag, having them show
up not only a new/unread, but with certain colors. You can filter not
only on subject but also on sender (for better or worse ;-) ), text
occurring in the body, etc...
This way, you can have the computer do the most tedious part, separating
"signal from noise", which largely helps to reduce the number of emails
you actually "have to read". For me, that is on average maybe 10-20% of
the daily emails.
And why do you want to delete any emails, unless they are complete and
utter nonsense/spam (which barely happens in any of the FPC mailing
lists at least)?.  I have all emails from the FPC lists going back to
early 2013, when I got by previous laptop and switched some accounts
from POP3 to IMAP, and it would just take a restore from some old backup
to get any previous emails back, probably at least to 2002 or so.
And if you are looking for a certain topic/keyword from past posts, you
can do a search just fine, which you might have to do anyway if you are
looking for something in a past thread, as I seriously doubt that you
remember exactly where and when someone posted that info you might be
looking for a few months later...

> Setting up thousands of filters is a time waster too...
Pick you poison... But, as far as setting up filters goes, most of it is
a one time thing. It might be a bit more if you just get started, but it
will reduce and become second nature over time if you keep using it,
saving you a lot of time in the long run. And TBird does filters much
better than any other email client out there right now, I barely miss
Eudora these days anymore...

Ralf


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Re: [fpc-other] What makes a Compiler project (like FPC) special?

[Paul Robinson]

Graeme Geldenhuys asked in Vol 108, Issue 27, "What makes a compiler project 
special?"
Well, I'm not a member of the FPC but I've worked on several compilers and I'll 
throw in my 0.02 Euro into the discussion.
> Since Florian mentioned that a compiler project is "rocket science" [not his 
> direct words, but he hinted at that] and totally different to any other 
> software 
> project... It has really bugged me... Why is it different, and What is 
> different?
I'm going to have to disagree here, and it may simply display my own ignorance 
of the subject, but, then again, even a stopped clock is right twice a day.
A compiler is a "language processor," an application that converts code in one 
language into something else. If it's a translating compiler it converts it to 
another language. If it's a language compiler it converts it to binary code or 
potentially to assembly language. (I'm making a bit of a distinction in that a 
compiler that translates to assembly code isn't a "translator" because it is 
using the assembler to save some of the work in not "reinventing the wheel" and 
not having to create its own object file writer, and because compilers 
generating assembly are usually creating a finished output requiring no manual 
intervention. Most translators that change source from one (high level) 
language to another produce results that often require manual correction. Few 
translators produce "perfect" high-level to high-level conversions without some 
work. They'll do the "heavy lifting" but often minor "tweaks" or checking is 
required by the person.) 

At its core, a language processor is a text processing application. It takes a 
fixed combination of rules on what the programmer can and must "say" in order 
to specify the particular actions they want a program to accomplish. Given 
these rules, which are called "grammars" the programmer describes the program 
and the compiler takes that description and turns it into the target 
representation of that description.
In the case of a translator, it produces a new program in a different language. 
Or it may be the same language but converted to a different dialect, such as a 
translation from a different Pascal compiler, or a conversion from HP Cobol to 
IBM Mainframe Cobol, or conversion from C or Fortran to something newer.
Most language processors have gone to using parser generators in order to 
reduce the work involved in scanning a source language. Some may simply do 
language scanning directly. Most older Pascal compilers used "symbol 
substitution" in which as the language was scanned, it would create a symbol 
identifying what had been found. Whether it was an unrecognized word (which 
would indicate a user identifier), a symbol (like :, >, /, comma, etc) or a 
keyword (USES, UNIT, BEGIN, etc). Then the internal "current symbol" was set to 
the value of that symbol. 

Most compilers had about a 1 byte lookahead so that it could determine if it 
was a single byte symbol (comma, ^, or ' ) or a multibyte symbol which may be 
different depending on the second byte (> followed by an identifier vs. >=, : 
vs :=, < vs <> or <=). Okay, all of this was reasonable until object 
orientation came into use.
When one uses a variable, or a constant, which one are you using? Well, it 
depends on the "scope." If you have I defined in the main program (or in the 
definitions of a UNIT), your reference is to that one. If you're inside a 
procedure, function, method or other similar construct and you define I there, 
it uses that one/ But what if your program - or UNIT - calls several others 
UNITs each having a variable I defined, which one does it use? The first one? 
The last one?
Now, the plot thickens if you reference an object. An identifier in that object 
can be fixed or virtual. In which case, it may not be certain until execution 
time which one is being used, a variable or procedure in the base class or an 
overridden one in a descendant object. So a compiler has to read the tables in 
a unit in order to discover what items are visible and where they are in that 
unit, also to know what kind of variable (or procedure, or function) it is, and 
what is legal to do with it (can't add a 64-bit integer to an 8-bit unsigned 
byte because they're not compatible but you can do it the other way around.)

But this is still the translation of symbols and assigning them attributes 
including whether they are a standalone item (like a unit), a dependent item 
(like a variable in a program) or an internal item (like a field in a record or 
a member of an object.) It requires you keep information about these things but 
I don't think this is any worse than the work involved in a video game in 
holding state information about the game map, the player character (PC), 
non-player characters (NPCs), enemies, objects the player can hold (guns, 
Portal Device, radio) or the use or consume (money, ammo, health).
The last time I did a compile of the full compiler, it 

Re: [fpc-other] What makes a Compiler project (like FPC) special?

[noreply]

On 2017-05-25 16:04, mar...@stack.nl wrote:

   But Florian's statements just bugged me, and I see no proof to
   convince me otherwise - a compiler is just a complex project.
   Nothing "special" as he claimed it to be.


I do think Nikolay's point of it being more interconnected describes it
fairly well. There are no narrow interfaces that are natural seams for
modularization inside the compiler.



I've always wanted to modularize the fpc compiler in such a way that you 
could use the fpc compiler for not just compilation, but 
checking/parsing the code for other reasons, i.e. fpdoc.

But this would likely make the compiler slower.

And another modular compiler idea is that you could embed a relational 
database language inside fpc as a plugin, such as SQL or TutorialD, but 
these are just pipe dreams - and a plugin/modular compiler likely will 
be slower to compile code since there are now more things the compiler 
has to choose to do, more wrappers. But, I don't know for certain.


There was also that strange, but rejected, object oriented plugin 
compiler that someone was working on at one time.. Was it Dodi? I forget 
his name. Maybe the delphi decompiler guy?

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Re: [fpc-other] What makes a Compiler project (like FPC) special?

[noreply]

On 2017-05-25 16:21, Nikolay Nikolov wrote:

On 05/26/2017 12:16 AM, Graeme Geldenhuys wrote:

On 2017-05-25 22:04, Marco van de Voort wrote:

There are no narrow interfaces that are natural seams for
modularization inside the compiler.


Yet the “packages” and “rtl” directories is just that - which by the 
way is part of the FPC project.

"packages" - yes. But "rtl" is a lot more tightly coupled to the
"compiler" than you think.



Indeed, all the string routines and reference counting is tied to the 
compiler.

I learned this when I had an idea for a new string type..

A string(1000) instead of string(255) or a string(arbitrary). Fixed 
length string that can go beyond 255. Oberon has it. When you introduce 
a new type into the RTL that is not a class, but a type that is part of 
the language itself you have to add all the routines in sysutils to deal 
with this type, change the compiler, make overloaded string routines.


And system.pp is tightly intertwined with the compiler and is almost a 
run time for the language. Not as much like Plain C, but probably even 
Plain C has some connections to the include files and the compiler


Then there is writeln too which is tied to the compiler as it is like a 
varargs, but accepts multiple types. So if you introduce a new 
string(1000) into the compiler, writeln also has to be modified to 
accept this new type as a parameter. But not just writeln, other things 
too.


If you don't have this intertwined and tightly integrated system you 
just end up putting things into a Lisp like system where it is all 
defined by not the compiler/rtl, but the libraries/modules which changes 
the language at run time. Powerful but also double edged sword that 
makes the language redefinable - open for abuse and misuse, such as 
lisp's ability to basically rechange the entire language to any thing 
you want as long as you include (some(brackets)) but everything else is 
up for grabs.

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Re: [fpc-other] What makes a Compiler project (like FPC) special?

[Florian Klämpfl]

Am 25.05.2017 um 16:18 schrieb Graeme Geldenhuys:
> This is directed at Florian primarily, but any other FPC core member is 
> welcome to chip in.
> 
> different to any other software project... It has really bugged me...
> Why is it different, and What is different?

Because they are basically a mess of spaghetti code and modules :) And this is 
not the writers fault
but simply their nature, they are a very complex piece of software were 
everything is inter winded.
In theory, everything sounds simple: one has a front end consisting of a 
scanner and a parser and a
back end consisting of an optimizer, a code generator and an assembler. Front 
end and back end are
accessing the symbol tables. However, in practice things look different. We try 
to keep fpc layered
and everything, nevertheless, the unit dependency graph looks terrible, see 
attachment (resized, I
can send a full fledged pdf if someone is interested). Simple things often mean 
that one has to dig
upside down and one is often bitten by several side effects or interferences of 
changes. I am really
familiar with the code of FPC, but I do not want to know the hours I spent in 
e.g. r36325 (which is
basically 100 lines of new code, rest is copy and moving code around) due 
to such effects.
Code sample for the "spaghetti" nature, just look at the needtemp function in 
fpc/compiler/ncal.pas
at line 4589: it determines if an argument of an inlined subroutine needs to be 
copied to a temp.
The code is commented very well, it is almost literate programming, everything 
is split into
multiple if statements, nevertheless it is very unreadable. Of course,
EveryIfStatmentCouldBeMovedToAnExtraFunctionWithADescribtiveLongName, but I 
doubt that it makes it
more readable in the sense of being understandable.
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