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  • #41
  • Edited 6:59am Jul 10, 2010 6:46am | Edited 6:59am
Quoting dinhero
I think I will simply download Lazarus.... by the way what is this advantage that Lazarus have and Delphi not ?

so about the code: when I am doing as this :

[code]
function foo(x: double; y: PChar): PChar; stdcall;
var...
Did you try my suggestion with ansistring(y) instead of y?

You could also try to declare a variable of type ansistring and fill this variable with ansistring(y) and then do the string concatenation with that variable instead of using y directly.

It would be interesting to not simply give up at this point and instead try to find out what it needs to make this code run with Delphi, this would provide some interesting insights.

The two main advantages of Lazarus over Delphi are for me:

 

  1. it is open source and this means it will exist forever and not suddenly disappear or be otherwise unavailable or unusable like it inevitably happens to all commercial software products sooner or later. (Hint: Kylix)
  2. it is available on more platforms than only windows, it is available for Linux (important for me) and Mac and for the most commonly used different processor architectures and I can just simply compile the same program without any changes or any other special prerequisites on any of the supported platforms.

  • #42
  • Jul 10, 2010 2:00pm Jul 10, 2010 2:00pm
Hi 7bit !

I tried everything without any solution ! also, the dll produces in delphis is 4 times bigger than the one (same code) from lazarus... but this is not really the point, I just want to code something working and efficient.

So until now I am coding on the both system... look like both have advantage and disadvantaged at the end... so until I have my dll working...

I have a question : I download the beta version of the last lazarus (which look like to be the only one available), does it stable ?
  • #43
  • Edited 3:09pm Jul 10, 2010 2:31pm | Edited 3:09pm
Quoting dinhero
download the beta version of the last lazarus (which look like to be the only one available), does it stable ?
Lazarus is quite stable. The creators of Lazarus are perfectionists striving for perfection. It seems perfection for some of them is defined as V1.0 but every perfectionist also knows that perfection can never be reached, so I think they will be at 0.9.99.99999 release candidate 8 in ten years while the software itself would have deserved a "marketing friendly" version number of 5.0 already years ago if it were a commercial project. There have been many discussions about this at the mailing list already but they all seem to suffer the perfectionism syndrome, but this should be seen as a positive quality of a software developer and as a sign for extremely good software.

The compiler itself, which is a separate project, is at 2.5 already and 2.4.3 is used in the latest Lazarus builds. The Lazarus Project is only the IDE and the Lazarus Components Library, the compatible clone and cross-platform re-implementation of Borland's VCL.

You can also try to go to the daily snapshots website: http://www.hu.freepascal.org/lazarus/ and download the latest snapshot. For windows 32 bit this would currently be:

Lazarus + fpc 2.4.3 win32 Lazarus-0.9.29-26562-fpc-2.4.3-20100710-win32.exe

The "Lazarus fixes + fpc 2.4.0" is an older branch, supposed to be more stable than the latest nightly but with only important bugfixes merged into it, but I recently read something in the mailing list that there were problems with the fixes branch and it did not work at all for some time.

I am usually downloading one of the very latest bleeding edge nightly builds from time to time and use it until I find a newer one that works just as good as the previous one or has some bugs fixed or other improvements. These nightly builds usually are very stable, they are the versions the developers themselves are using (to work on Lazarus itself, Lazarus is entirely written in Lazarus), they try to keep this branch always working as good as possible, most of the manpower is concentrated there.
  • #44
  • Jul 10, 2010 2:41pm Jul 10, 2010 2:41pm
Quoting dinhero
also, the dll produces in delphis is 4 times bigger than the one (same code) from lazarus
If you want to further decrease the code size look into the project options under "Linking" turn off all debugging info and line numbers and turn on "strip symbols" for the final release. Also always enable "smart linking" and "smart linkable". This should further decrease the size of the generated .exe and .dll files.
  • #45
  • Jul 10, 2010 3:13pm Jul 10, 2010 3:13pm
Quoting 7bit
If you want to further decrease the code size look into the project options under "Linking" turn off all debugging info and line numbers and turn on "strip symbols" for the final release. Also always enable "smart linking" and "smart linkable". This should further decrease the size of the generated .exe and .dll files.
Thank you for everything 7bit, your answer and contribution are great !!

So may I have a question : you say :

Quote
To create a new DLL project (if you started Lazarus for the first time) click on Project -> new project -> Library. Give it a meaningful name and save it into an empty folder. The project will initially consist of only two files. An .lpi file containing all compiler settings and and .lpr file containing the source code, these two files are all you need to backup, pass on to your colleagues or manage in a source code repository. Additional units (if you decide to split up bigger projects) are saved as individual .pas files.

But when I do create a new project as a dll, lazarus actually produce more file :
http://www.forexfactory.com/attachme...1&d=1278792506

Then, when I am trying to compile my project, it does not produce a dll but an .exe file. I mean in case of a .dll it does produce .exe one.

I tried many time since 2 hours, as well just copying pasting your code inside a new library project. It does give :

Inserted Code
library Project1;

{$mode objfpc}{$H+}

uses
  Classes
  { you can add units after this };

{$IFDEF WINDOWS}{$R AHL1.rc}{$ENDIF}

begin
end.

But then, when compiled it just produce an .exe.

I google to look for answer to this problem but it seems that it happen with other, but no one answer : so do I miss something in the configuration maybe ?
Attached Image (click to enlarge)
Click to Enlarge Name: lazar_pic.JPG Size: 71 KB
  • #46
  • Edited 4:36pm Jul 10, 2010 3:50pm | Edited 4:36pm
Quoting dinhero
But when I do create a new project as a dll, lazarus actually produce more file :
The .lpi and the .lpr are the ones that contain all information, the other ones are generated.

Regarding your screenshot: I cannot see anything there. Please turn off the hiding of file name extensions in your windows explorer. How can you productively use your computer if you have set it to hide half of every filename (the important half even) from you (and from me when I look at your screenshot)?

Quote
Then, when I am trying to compile my project, it does not produce a dll but an .exe file. I mean in case of a .dll it does produce .exe one.
I cannot reproduce this. If I create a new library project and then immediately compile it without doing anything further then I will find the .dll file with the name of the project inside the folder lib/i386-win32.

If I set a target filename in the project options i will get a .dll file in the projects folder. If I give it a name without the extension .dll then I will also correctly end up with a .dll file.

If i wrongly/accidentally have set a target filename ending with .exe then it will of course name the file .exe as requested but it won't be an exe, it will still be a .dll, only with the wrong name.
  • #47
  • Edited 4:48pm Jul 10, 2010 4:34pm | Edited 4:48pm
Also a few postings ago you wrote that the dll example worked with lazarus, so you must have changed something in the meantime. If you completely messed up all settings try to restore them all to their defaults, maybe even do a fresh install if nothing helps.

Also be careful with the option "Use comiler settings as default for new projects", this might cause confusion if you start a new project and don't remember all the special settings you have made in the last project (and why), especially if you are still in the experimenting phase until you are familiar with all the settings.

It might for example have remembered the name for the target filename and if you previously made some experiments with .exe files and specified an .exe filename and checked "use as default for new proects" and then all new projects will use this target filename and even libraries will then rename their output file to this .exe filename because it is in the project options until you remove it and save as new defaults again.
  • #48
  • Jul 10, 2010 4:54pm Jul 10, 2010 4:54pm
Quoting 7bit
The .lpi and the .lpr are the ones that contain all information, the other ones are generated.

..........

..............

If i wrongly/accidentally have set a target filename ending with .exe then it will of course name the file .exe as requested but it won't be an exe, it will still be a .dll, only with the wrong name.
Hi, it working now ! Yea you correct I have to set my windows setting in a more technical way ! So in all the case, now Lazarus compile .dll according to my project type choice.

But I had to do something a litle different : sincerely until that the it was systematically compiling an .exe.
So I had to create a new project and to chose a completly different type, neither an .exe app or dll, I chosed FPC Unit console ect... then compile a project under it. / I close / Open Lazarus again / and create a new project as a library (dll), so now it is working fine.

Maybe they could be cache memory or something somewhere and it need to be reset... or maybe because my installation is new.

Thanks for everything 7bit !
Attached Image (click to enlarge)
Click to Enlarge Name: lazar_pic2.JPG Size: 80 KB
  • #49
  • Jul 11, 2010 2:55pm Jul 11, 2010 2:55pm
Just found this which might be relevant for the problem with the .dll being outputted as .exe
http://www.lazarus.freepascal.org/in....msg39170.html
  • #50
  • Edited Jul 14, 2010 2:41pm Jul 13, 2010 5:20pm | Edited Jul 14, 2010 2:41pm
Quoting 7bit
Maybe Delphi is a bit buggy and does not do this correctly. Maybe you should try to explicitely convert it to an ansistring first:
Inserted Code
[b]function[/b] foo(x: double; y: PChar): PChar; stdcall;
[b]var[/b]
  s :ansistring; // reference counted and memory managed strings.

[b]begin[/b]
[color=SeaGreen]  // our PChar will be copied into an ansistring [/color][color=SeaGreen][b][color=SeaGreen]automatically[/color][/b],
  // [b][color=SeaGreen](well, maybe not so automatically in delphi, so try to ecplicitely convert it)[/color][/b]
  // no need to worry about the ugly details of memory allocation.[/color]
  s := 'Hello ' + FloatToStr(x) + ' ' + [color=Red]ansistring(y)[/color] + '!';

 [color=SeaGreen] // cast it back into a pointer. Metatrader will copy the
  // string from the pointer into it's own memory.[/color]
  result := PChar(s);
[b]end;[/b]
On this issue I have always found that delphi inconsistently sets the length of the string when a Pchar is type cast to a string (ansistring) although it does always copy ALL the data in the Pchar. (As I recall Delphi is fine casting its own Pchars to strings but not those from outside sources)

So to ensure perfect pchar --> string type casting in delphi you should :

Var s : string;
var p : pchar;

s := string(p);
setlength(s,strlen(p));


Its anoying as bugs can easily be introduced if you forget, but so long as you remember it gets the job done.


Its Also a bad idea to use a local string to use as the return storage to MT4
For most (normal) string lengths this will be fine but if you have a huge string (in my experience > 14Kb) then it is common for some of the string to go missing.

This is because MT4 is copying data from a variable whose scope has just been removed.

IE the local string s is being destroyed by the DLL language because the function has ended and local vars need to be cleaned up. This is occuring whilst Mt4 is copying the string. So in the case of a large string not all the data will be copied before the DLL language destroys it.
  • #51
  • Mar 25, 2011 12:39am Mar 25, 2011 12:39am
Quoting rangebound
[code]
Var s : string;
var p : pchar;

s := string(p);
setlength(s,strlen(p));
Is it possible to somehow automate this? Maybe through compiler derivatives or whatnot?


I have a general question about Lazarus. Am I correct in understanding that most code Win32-specific code that is publicly available for Delphi is not easily usable in Lazarus? If so, what practical advantage does Lazarus have over Delphi? I have been using Lazarus for the past week or so and I really like it, but I am wondering if I should use delphi instead.

Does interaction with MT4 work in the same exact manner in Delphi? Is there any difference in PChar - > Ansistring conversion or anything I should know about before I try delphi?
  • #52
  • Mar 25, 2011 4:00am Mar 25, 2011 4:00am
Quoting mfurlend
I have a general question about Lazarus. Am I correct in understanding that most code Win32-specific code that is publicly available for Delphi is not easily usable in Lazarus? If so, what practical advantage does Lazarus have over Delphi? I have been using Lazarus for the past week or so and I really like it, but I am wondering if I should use delphi instead.
You will be able to use many of the win32-specific code directly in Lazarus and compile it for windows but you will need some heavy rewriting if you want to make such code compile under Linux or Mac.

The recommendation to not use win32 specific API is simply to not restrict yourself to the windows platform. If you start a new project from scratch you should only use the cross platform APIs of RTL, FCL and LCL and additional cross platfom components which replace pretty much everything you could ever do with the Windows API.

Lazarus has the advantage that you can develop in a delphi-like manner (and also to some extent reuse existing Delphi code) and compile the same identical code on many different platforms (while Delphi is only available for i386/windows). The second (and for some people the main) advantage is that Lazarus is Open Source and thus no commercial entity can ever take it away from the community anymore (remember the Kylix debacle).


Quote
Does interaction with MT4 work in the same exact manner in Delphi? Is there any difference in PChar - > Ansistring conversion or anything I should know about before I try delphi?

It should all be more or less exactly the same. The posting you quoted with the string casting is one of the rare exceptions where some tiny details are slightly different (and not even documented, this particular thing seems to be a bug in Delphi).

If you don't own Delphi yet, then there is no reason to buy it. The general trend is that people are porting their code from Delphi to Lazarus, not the other way around. Lazarus is the escape pod¹ that will be needed when someone on the command bridge of the Delphi space ship presses the self-destruct button (again).


BTW: There is a new version of Lazarus underway, after almost two years of hard work the 0.9.30 version will soon be released. Its tagged in SVN already, release candidates have been tested already, its only a matter of days now.

_____
¹) It's actually much much more than that.
  • #53
  • Edited 6:13pm Mar 25, 2011 5:32pm | Edited 6:13pm
In that case I will stick with Lazarus . I really appreciate your "making DLLs with Lazarus" thread; it completely changed the way I program this stuff.

I've got a question if you have a minute -

I made a program in Lazarus that uses the TSimpleIPC package to allow communication between two separate MT4 Testers.

I use TSimpleIPCServer.OnMessage to process messages in the server part. The problem is that the client does not know in advance when the server will become available.

The way I have it coded right now is that the client keeps checking if the server is available - if not it will Sleep(5) and then check again.

sent := False;
repeat
if client1.ServerRunning then
begin
client1.Connect;
client1.SendStringMessage(outstr);
sent := True;
client1.Disconnect;
end else
begin
Sleep(5);
end;
until (sent = True);

There must be a better way to do this; it seems wrong that I am using Sleep().
Is it possible to attach an event handler to the TSimpleIPCClient.ServerRunning function?
  • #54
  • Last Post: Mar 29, 2011 5:07am Mar 29, 2011 5:07am
Quoting mfurlend
Is it possible to attach an event handler to the TSimpleIPCClient.ServerRunning function?
I haven't used TSimpleIPCClient yet. AFAIK it is implemented with named pipes and I don't know of any mechanisms to have an event triggered when the pipe comes into existence, but I'm not entirely sure.

But you could make each application start its own IPC server and make them connect each other mutually. Maybe this might lead to some cleaner/easier code.


BTW Lazarus 0.9.30 was finally released yesterday :-)
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