Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Marcos Douglas B. Santos 
On Wed, Sep 6, 2017 at 10:17 PM, Ryan Joseph  wrote:
>
>> On Sep 6, 2017, at 10:20 PM, Sven Barth via fpc-pascal 
>>  wrote:
>>
>> You're missing that FHook was declared as IHook, not THook.
>>
>
> In terms of memory why does it matter how it was declared? The memory was 
> allocated in Create() so the declaration is just relevant for the assignment 
> of the new memory. Is FPC doing something magic behind the scenes?
>

Because COM interface variables are automatically released.
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Ryan Joseph 

> On Sep 6, 2017, at 10:20 PM, Sven Barth via fpc-pascal 
>  wrote:
> 
> You're missing that FHook was declared as IHook, not THook.
> 

In terms of memory why does it matter how it was declared? The memory was 
allocated in Create() so the declaration is just relevant for the assignment of 
the new memory. Is FPC doing something magic behind the scenes?

Regards,
Ryan Joseph

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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Paul Breneman 

On 09/06/2017 05:21 PM, Marc Santhoff wrote:

On Mi, 2017-09-06 at 23:06 +0200, Bo Berglund wrote:

On Wed, 06 Sep 2017 22:52:12 +0200, Bo Berglund
 wrote:


I have now added extra binary logging to the relaying program only to
find that the data received and processed are missing about 50 k of
the 1M transmission.
Next I will edit serial.pp and up the buffers from 2K to 60K or so.


By the way:
I have sent the Delphi test program I am debugging over to people at
the remote location and they have connected their laptop directly to
the data system and with that setup there is no data loss.
So this leaves me with only the Lazarus/FPC network relaying app to
fix...


Could that be some sort of timeout?

You're setting

   FTcpComm.ReadTimeout := 30;

but I have no idea what order of magnitude this 30 is. Maybe streching
the timeout a little bit can help?

I had several cases of timeout problems using RS232 over TCP.


I could also create another test program, a serial sniffer that could
be set up to just log whatever appears on the serial lines. I need a
3-way cable for that of course.


Such thing does exists, I only forgot the name(s), ;)

HTH,
Marc



There are two links in the bottom paragraph on this page:
http://ctrlterm.com/custom.htm

Regards,
Paul
www.ControlPascal.com
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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread José Mejuto 

El 06/09/2017 a las 21:22, Bo Berglund escribió:

   Inc(RxTcp, Length(Buf));
   SerWrite(FComH, Buf[0], Length(Buf));
   Inc(TxSer, Length(Buf));
Where could I be losing incoming serial data?


Hello,

Where do you check that "Length(Buf)" has been sent ?

if SerWrite(FComH, Buf[0], Length(Buf))<>Length(Buf) then Raise 
Exception.Create("KBOOM");


--

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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Marc Santhoff 
On Mi, 2017-09-06 at 23:06 +0200, Bo Berglund wrote:
> On Wed, 06 Sep 2017 22:52:12 +0200, Bo Berglund
>  wrote:
> 
> >I have now added extra binary logging to the relaying program only to
> >find that the data received and processed are missing about 50 k of
> >the 1M transmission.
> >Next I will edit serial.pp and up the buffers from 2K to 60K or so.
> 
> By the way:
> I have sent the Delphi test program I am debugging over to people at
> the remote location and they have connected their laptop directly to
> the data system and with that setup there is no data loss.
> So this leaves me with only the Lazarus/FPC network relaying app to
> fix...

Could that be some sort of timeout?

You're setting

  FTcpComm.ReadTimeout := 30;

but I have no idea what order of magnitude this 30 is. Maybe streching
the timeout a little bit can help?

I had several cases of timeout problems using RS232 over TCP.

> I could also create another test program, a serial sniffer that could
> be set up to just log whatever appears on the serial lines. I need a
> 3-way cable for that of course.

Such thing does exists, I only forgot the name(s), ;)

HTH,
Marc


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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Bo Berglund 
On Wed, 06 Sep 2017 22:52:12 +0200, Bo Berglund
 wrote:

>I have now added extra binary logging to the relaying program only to
>find that the data received and processed are missing about 50 k of
>the 1M transmission.
>Next I will edit serial.pp and up the buffers from 2K to 60K or so.

By the way:
I have sent the Delphi test program I am debugging over to people at
the remote location and they have connected their laptop directly to
the data system and with that setup there is no data loss.
So this leaves me with only the Lazarus/FPC network relaying app to
fix...

I could also create another test program, a serial sniffer that could
be set up to just log whatever appears on the serial lines. I need a
3-way cable for that of course.


-- 
Bo Berglund
Developer in Sweden

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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Bo Berglund 
On Wed, 06 Sep 2017 22:52:12 +0200, Bo Berglund
 wrote:

>Next I will edit serial.pp and up the buffers from 2K to 60K or so.

Question:
If I edit the content of serial.pp (the one that is brought up by
right clicking and "Find declaration") such that it looks like this:

const   bufSize= 61440; //2048;

will it be used the next time I test run my application or must I do
some kind of "installation" like updating Lazarus or similar for it to
be used?


-- 
Bo Berglund
Developer in Sweden

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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Bo Berglund 
On Wed, 06 Sep 2017 22:27:49 +0200, Marc Santhoff
 wrote:

>On Mi, 2017-09-06 at 21:22 +0200, Bo Berglund wrote:
>> Where could I be losing incoming serial data?
>
>Only for completeness:
>
>Can you rule out problems reagrding the hardware side? Mabe there are
>some weak line drivers or a faulty cable involved?
>
>Worth checking, at least.
>
Well,
I am using a 4-way USB to Serial unit and the cable (nullmodem)
connects two adjacent ports and is about 50 mm long...
This cable has never failed ever before.

I have now added extra binary logging to the relaying program only to
find that the data received and processed are missing about 50 k of
the 1M transmission.
Next I will edit serial.pp and up the buffers from 2K to 60K or so.

-- 
Bo Berglund
Developer in Sweden

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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Marc Santhoff 
On Mi, 2017-09-06 at 21:22 +0200, Bo Berglund wrote:
> Where could I be losing incoming serial data?

Only for completeness:

Can you rule out problems reagrding the hardware side? Mabe there are
some weak line drivers or a faulty cable involved?

Worth checking, at least.

HTH anyhow,
Marc


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Re: [fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Mark Morgan Lloyd 

On 06/09/17 18:45, Bo Berglund wrote:

I have created a simple application which relays data from anapplication I am 
debugging in Windows7 to/from a remotely locatedembedded data system.I use the 
built-in fpc Serial unit to handle the serial data and anIndy10 TIdTcpClient 
for the network part.Data coming in on the serial port are mirrored out to the 
remote TCPserver and data returned from that server are mirrored to the 
serialport.The Windows application only uses RS232 for this type 
ofcommunication.At the remote location I have a Raspberry Pi uint where I 
haveinstalled and configured ser2net to do the same job in the remotelocation.
My relaying application displays the number of bytes received andtransmitted on 
the interfaces so I can see what is going on.
This scheme has worked fine for most commands and data transfers Ihave checked, 
but now I have run against a brick wall...
There is a pair of commands designed to read and write a large sectionof the 
system CMOS RAM memory (where the data file system resides).When I try to write 
a 1 Mbytes big buffer the byte count in my relayerdoes not reach the correct 
number. The Windows application I amdebugging sends all of the bytes out the 
serial port (I have loggedthis), but the relayer seems to lose some data and 
therefore thetransfer fails. The binary protocol specifies at the start how 
manybytes are to be transferred (0x0FF000 or 1044486 decimal), then itsends the 
data followed by a two-byte checksum. The data system shallrespond with NAK or 
ACK depending on the outcome of the checksumverification.The problem is that 
when the Windows app is done sending the datasystem is still missing many 
kilobytesSo no ACK is returned, it is still in receive mode.
Now I am looking at the Serial unit in order to figure out how buffersizes 
influence the performance. Apparently both Tx and Rx buffers areset (hardcoded) 
to 2048, which feels like a bit low to me.
Is there some hidden property that makes it possible to increase thisvalue?What 
is the maximum size one can set it too?


Not that I was responsible for. Refer to the Windows API for any limits.

--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]
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[fpc-pascal] Using Serial in a TCP/RS232 gateway, how to set buffer sizes?

2017-09-06 Thread Bo Berglund 
I have created a simple application which relays data from an
application I am debugging in Windows7 to/from a remotely located
embedded data system.
I use the built-in fpc Serial unit to handle the serial data and an
Indy10 TIdTcpClient for the network part.
Data coming in on the serial port are mirrored out to the remote TCP
server and data returned from that server are mirrored to the serial
port.
The Windows application only uses RS232 for this type of
communication.
At the remote location I have a Raspberry Pi uint where I have
installed and configured ser2net to do the same job in the remote
location.

My relaying application displays the number of bytes received and
transmitted on the interfaces so I can see what is going on.

This scheme has worked fine for most commands and data transfers I
have checked, but now I have run against a brick wall...

There is a pair of commands designed to read and write a large section
of the system CMOS RAM memory (where the data file system resides).
When I try to write a 1 Mbytes big buffer the byte count in my relayer
does not reach the correct number. The Windows application I am
debugging sends all of the bytes out the serial port (I have logged
this), but the relayer seems to lose some data and therefore the
transfer fails. The binary protocol specifies at the start how many
bytes are to be transferred (0x0FF000 or 1044486 decimal), then it
sends the data followed by a two-byte checksum. The data system shall
respond with NAK or ACK depending on the outcome of the checksum
verification.
The problem is that when the Windows app is done sending the data
system is still missing many kilobytes
So no ACK is returned, it is still in receive mode.

Now I am looking at the Serial unit in order to figure out how buffer
sizes influence the performance. Apparently both Tx and Rx buffers are
set (hardcoded) to 2048, which feels like a bit low to me.

Is there some hidden property that makes it possible to increase this
value?
What is the maximum size one can set it too?


-- 
Bo Berglund
Developer in Sweden

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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Graeme Geldenhuys 

On 2017-09-06 16:27, Tony Whyman wrote:

Is history repeating itself:


Quite likely. It did all sound awfully familiar. :-)

I've now [finally] added this to my "Personal Programming Notes" archive 
(yes, I actually have such a file). So hopefully now I will not forget 
about the gotcha of memory leaks and reference counted objects.


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-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Michael Van Canneyt 



On Wed, 6 Sep 2017, Tony Whyman wrote:


Is history repeating itself:

http://lists.freepascal.org/pipermail/fpc-pascal/2016-August/048579.html


Any historian will confirm this :)

Michael.
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Tony Whyman 

Is history repeating itself:

http://lists.freepascal.org/pipermail/fpc-pascal/2016-August/048579.html


On 06/09/17 09:31, Graeme Geldenhuys wrote:

Hi,

Playing with this small sample application to answer another question 
in this mailing list, I noticed the sample application has a memory 
leak. For the life of me I can't see why or how to resolve it.


I tested with FPC 2.6.4, 3.0.2 and 3.0.4-rc1 under 64-bit FreeBSD.

===[ project1.pas ]
program project1;

{$mode objfpc}{$H+}
{$interfaces COM}

type
  IHook = interface
['{4BCAEDD8-92D8-11E7-88D3-C86000E37EB0}']
procedure DoIt;
  end;

type
  THook = class(TInterfacedObject, IHook)
  private
procedure DoIt;
  end;

  procedure THook.DoIt;
  begin
writeln(ClassName + ' did it');
  end;

type
  TBaseClass = class(TInterfacedObject, IHook)
  private
FHook: IHook;
property Hook: IHook read FHook implements IHook;
  public
constructor Create;
destructor Destroy; override;
  end;

  constructor TBaseClass.Create;
  begin
FHook := THook.Create;  // FPC 2.6.4 reports a memory leak here
  end;

  destructor TBaseClass.Destroy;
  begin
// nothing to do here
  end;


var
  base: IHook;

begin
  base := TBaseClass.Create;
  base.DoIt;
  base := nil; // just to see if it helped with the memory leak - it 
doesn't


end.
==[ end ]==


When I run the program, the output is as follows:

[t1]$ ./project1
THook did it
Heap dump by heaptrc unit
4 memory blocks allocated : 115/120
2 memory blocks freed : 51/56
2 unfreed memory blocks : 64
True heap size : 1114112 (32 used in System startup)
True free heap : 1113696
Should be : 1113760
Call trace for block $00080072F180 size 32
  $00400379 line 35 of project1.lpr
Call trace for block $00080072F0C0 size 32



Personally I always use CORBA style interfaces, never reference 
counted COM style interfaces. So my programs normally don't have this 
issue, and I use interfaces a lot.





Regards,
  Graeme



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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Sven Barth via fpc-pascal 
Am 06.09.2017 17:03 schrieb "Ryan Joseph" :
>
>
> > On Sep 6, 2017, at 8:03 PM, Graeme Geldenhuys <
mailingli...@geldenhuys.co.uk> wrote:
> >
> > I couldn't call .Free because FHook was a interface reference type of
type IHook, not THook.
>
> But TInterfacedObject is a class isn’t it? Then you call FHook :=
THook.Create; so a I’d expect a Free(). What am I missing?
>
> type
>  THook = class(TInterfacedObject, IHook)
>  private
>procedure DoIt;
>  end;

You're missing that FHook was declared as IHook, not THook.

Regards,
Sven
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Ryan Joseph 

> On Sep 6, 2017, at 8:03 PM, Graeme Geldenhuys  
> wrote:
> 
> I couldn't call .Free because FHook was a interface reference type of type 
> IHook, not THook.

But TInterfacedObject is a class isn’t it? Then you call FHook := THook.Create; 
so a I’d expect a Free(). What am I missing?

type
 THook = class(TInterfacedObject, IHook)
 private
   procedure DoIt;
 end;

Regards,
Ryan Joseph

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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Graeme Geldenhuys 

On 2017-09-06 11:33, Marcos Douglas B. Santos wrote:

You have resolved just by change FHookInstance
as a class, not an Interface, plus using TAggregatedObject too.


Ah yes, that seems to work too. Many thanks for pointing that out.

So here is another implementation that works with NO memory leaks.

[ project1.pas ]
program project1;

{$mode objfpc}{$H+}
{$interfaces COM}

type
  IHook = interface
['{4BCAEDD8-92D8-11E7-88D3-C86000E37EB0}']
procedure DoIt;
  end;

type
  THook = class(TAggregatedObject, IHook)
  private
procedure DoIt;
  end;

  procedure THook.DoIt;
  begin
writeln(ClassName + ' did it');
  end;

type
  TBaseClass = class(TInterfacedObject, IHook)
  private
FHookInstance: THook;
property Hook: THook read FHookInstance implements IHook;
  public
constructor Create;
destructor Destroy; override;
  end;

  constructor TBaseClass.Create;
  begin
inherited Create;
FHookInstance := THook.Create(self);
  end;

  destructor TBaseClass.Destroy;
  begin
FHookInstance.Free;
inherited Destroy;
  end;


var
  base: IHook;

begin
  base := TBaseClass.Create;
  base.DoIt;

end.
==[ end ]===


Yeah, just as I said Interfaces are an advanced feature of the 
Object Pascal language. Lots of traps!


Bottom line:

NEVER code without enabling memory leak detection!!!  :)


Regards,
  Graeme

--
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http://fpgui.sourceforge.net/

My public PGP key:  http://tinyurl.com/graeme-pgp
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Graeme Geldenhuys 

On 2017-09-06 10:30, Ryan Joseph wrote:

FHook := THook.Create;

so you need a FHook.Free call? The class is THook = class(TInterfacedObject, 
IHook) right?


I couldn't call .Free because FHook was a interface reference type of 
type IHook, not THook.



Regards,
  Graeme

--
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http://fpgui.sourceforge.net/

My public PGP key:  http://tinyurl.com/graeme-pgp
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Marcos Douglas B. Santos 
On Wed, Sep 6, 2017 at 6:55 AM, Graeme Geldenhuys <
mailingli...@geldenhuys.co.uk> wrote:

>
> I can't remember ever [while using Delphi] being forced to implement a
> getter method in the "property ... implements..." line, but it seems that
> is the only way it remove memory leaks under FPC. Weird. :-/


You don't need this getter. You have resolved just by change FHookInstance
as a class, not an Interface, plus using TAggregatedObject too.

I wrote an article about it
http://objectpascalprogramming.com/posts/interfaces-delegacao-problemas-solucoes/

(use Google Translator).

Best regards,
Marcos Douglas
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Graeme Geldenhuys 

On 2017-09-06 10:55, Graeme Geldenhuys wrote:

On 2017-09-06 10:41, Sven Barth via fpc-pascal wrote:

I think THook needs to derive from TAggregatedObject, cause that couples
the reference counting to that of the controlling instance.


That seems to be heading in the right direction, but such a change on
its own doesn't seem to solve the two memory leaks either. I'll test
under Delphi XE which can report memory leaks to see what it does



Testing with Delphi XE - simply by changing THook to descend from 
TAggregatedObject. Under Delphi it also still reports a memory leak.




Either way, modifying the example to use a getter method AND
TAggregatedObject, I managed to get rid of both memory leaks. Here is
the working [memory leak free] code now:


Under Delphi XE, that was the only way to get rid of the memory leaks too.

So it seems for delegation and using "implements" you are forced to use 
a getter method and object variable (not interface reference variable) - 
under both FPC and Delphi. At least they are consistent. ;-)



ps:
  For those that didn't know Since Delphi 2006, add

  ReportMemoryLeaksOnShutdown := True;

  in your *.dpr file to enable memory leak detection.


Regards,
  Graeme

--
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http://fpgui.sourceforge.net/

My public PGP key:  http://tinyurl.com/graeme-pgp
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Ryan Joseph 

> On Sep 6, 2017, at 4:55 PM, Graeme Geldenhuys  
> wrote:
> 
> Either way, modifying the example to use a getter method AND 
> TAggregatedObject, I managed to get rid of both memory leaks. Here is the 
> working [memory leak free] code now:

Does the original code work if you just add the Free() call? I would expect it 
to leak without that.

Regards,
Ryan Joseph

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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Sven Barth via fpc-pascal 
Am 06.09.2017 10:31 schrieb "Graeme Geldenhuys" <
mailingli...@geldenhuys.co.uk>:
> type
>   IHook = interface
> ['{4BCAEDD8-92D8-11E7-88D3-C86000E37EB0}']
> procedure DoIt;
>   end;
>
> type
>   THook = class(TInterfacedObject, IHook)
>   private
> procedure DoIt;
>   end;
>
>   procedure THook.DoIt;
>   begin
> writeln(ClassName + ' did it');
>   end;

I think THook needs to derive from TAggregatedObject, cause that couples
the reference counting to that of the controlling instance.
See here:
http://docwiki.embarcadero.com/RADStudio/Tokyo/en/Implementing_Interfaces

Regards,
Sven
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Re: [fpc-pascal] implements

2017-09-06 Thread Graeme Geldenhuys 

On 2017-09-06 09:03, Ryan Joseph wrote:

For the sake of discussion can you see why it makes sense that “hook.” syntax 
would be implied because the class does indeed supposedly implement the 
interface? Everything about the syntax says that the methods in IHook should be 
in TBaseClass so I can’t help but feel like it was an omission or not fully 
finished.


"implements" in that example says that the implementation of the IHook 
interface is delegated to another class - THook. If you didn't define 
the property... implements in TBaseClass, then TBaseClass would have had 
to explicitly implement all methods of IHook. The implements means you 
can reuse the IHook implementation (thanks to THook) in many other 
classes too.


Granted I personally don't like the syntax for "implements", but that's 
what Borland came up with for Delphi, and FPC follows that syntax for 
compatibility reasons.


The other annoying thing of Object Pascal's Interface support is that 
you need to specify which interfaces you implement, even in descendant 
classes where the parent already implements a specific interface. But 
that's a whole other discussion. ;-)


Regards,
  Graeme

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Re: [fpc-pascal] implements

2017-09-06 Thread Sven Barth via fpc-pascal 
Am 06.09.2017 10:34 schrieb "Ryan Joseph" :
>
>
> > On Sep 6, 2017, at 2:50 PM, Graeme Geldenhuys <
mailingli...@geldenhuys.co.uk> wrote:
> >
> > There is NO need to make Hook public, because you can always get access
to that functionality via the Supports() call and get a reference to IHook.
>
> The Supports() call is the key takeaway here.
>
> For the sake of discussion can you see why it makes sense that “hook.”
syntax would be implied because the class does indeed supposedly implement
the interface? Everything about the syntax says that the methods in IHook
should be in TBaseClass so I can’t help but feel like it was an omission or
not fully finished. It would be messy to implement probably because you
would risk a number of name collisions with existing methods.

No it's definitely by design. If you use alias clauses ("procedure
IMyIntf.Foobar = Blubb") then you also won't have the interface's method in
your class, but only the alias. The method can only be accesssed by the
interface's method name by using an interface instance not the class
instance. The "implements" clause is just an advanced variant of that in
that it allows you to use a complete class (though you're still able to
implement selected methods of the interface in the base class which aren't
delegated then).

Regards,
Sven
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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Graeme Geldenhuys 

On 2017-09-06 09:37, Michael Van Canneyt wrote:

type
   TBaseClass = class(TInterfacedObject, IHook)
   private
 FHook: IHook;
 property Hook: IHook read FHook implements IHook;
   public
 constructor Create;
 destructor Destroy; override;
   end;

   constructor TBaseClass.Create;
   begin
 FHook := THook.Create;  // FPC 2.6.4 reports a memory leak here
   end;

   destructor TBaseClass.Destroy;
   begin
 // nothing to do here
   end;

You must free FHook here, because you are keeping a reference to the object,
not the interface.


I changed the destructor to the code shown below. Just so you know, I 
tried this before I posted the message, and it didn't make any 
difference. FHook is a IHook interface reference, not a object 
reference. I can't change it either, otherwise FPC gives me a compiler 
error on the property ... implements...; line.


  destructor TBaseClass.Destroy;
  begin
inherited;
FHook := nil;
  end;

And the program output gives:

[t1]$ ./project1
THook did it
Heap dump by heaptrc unit
4 memory blocks allocated : 115/120
2 memory blocks freed : 51/56
2 unfreed memory blocks : 64
True heap size : 1114112 (32 used in System startup)
True free heap : 1113696
Should be : 1113760
Call trace for block $00080072F180 size 32
  $00400379 line 35 of project1.lpr
Call trace for block $00080072F0C0 size 32


Still 2 memory leaks. :-(

Regards,
  Graeme

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http://fpgui.sourceforge.net/

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Re: [fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Michael Van Canneyt 



On Wed, 6 Sep 2017, Graeme Geldenhuys wrote:


Hi,

Playing with this small sample application to answer another question in 
this mailing list, I noticed the sample application has a memory leak. 
For the life of me I can't see why or how to resolve it.


I tested with FPC 2.6.4, 3.0.2 and 3.0.4-rc1 under 64-bit FreeBSD.

===[ project1.pas ]
program project1;

{$mode objfpc}{$H+}
{$interfaces COM}

type
  IHook = interface
['{4BCAEDD8-92D8-11E7-88D3-C86000E37EB0}']
procedure DoIt;
  end;

type
  THook = class(TInterfacedObject, IHook)
  private
procedure DoIt;
  end;

  procedure THook.DoIt;
  begin
writeln(ClassName + ' did it');
  end;

type
  TBaseClass = class(TInterfacedObject, IHook)
  private
FHook: IHook;
property Hook: IHook read FHook implements IHook;
  public
constructor Create;
destructor Destroy; override;
  end;

  constructor TBaseClass.Create;
  begin
FHook := THook.Create;  // FPC 2.6.4 reports a memory leak here
  end;

  destructor TBaseClass.Destroy;
  begin
// nothing to do here
  end;


You must free FHook here, because you are keeping a reference to the object,
not the interface. And you must call inherited. 
You must always call inherited in the destructor.


Michael.

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Re: [fpc-pascal] implements

2017-09-06 Thread Ryan Joseph 

> On Sep 6, 2017, at 2:50 PM, Graeme Geldenhuys  
> wrote:
> 
> There is NO need to make Hook public, because you can always get access to 
> that functionality via the Supports() call and get a reference to IHook.

The Supports() call is the key takeaway here.

For the sake of discussion can you see why it makes sense that “hook.” syntax 
would be implied because the class does indeed supposedly implement the 
interface? Everything about the syntax says that the methods in IHook should be 
in TBaseClass so I can’t help but feel like it was an omission or not fully 
finished. It would be messy to implement probably because you would risk a 
number of name collisions with existing methods.

Regards,
Ryan Joseph

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Re: [fpc-pascal] Free Pascal 3.0.4-rc1 released!

2017-09-06 Thread Graeme Geldenhuys 

On 2017-09-06 09:19, Graeme Geldenhuys wrote:

For example:


** Compiled with FPC 3.0.2 or FPC 3.0.4 - no line info



The complete sample application is here:


===[ project1.pas ]
program project1;

{$mode objfpc}{$H+}
{$interfaces COM}

type
   IHook = interface
 ['{4BCAEDD8-92D8-11E7-88D3-C86000E37EB0}']
 procedure DoIt;
   end;

type
   THook = class(TInterfacedObject, IHook)
   private
 procedure DoIt;
   end;

   procedure THook.DoIt;
   begin
 writeln(ClassName + ' did it');
   end;

type
   TBaseClass = class(TInterfacedObject, IHook)
   private
 FHook: IHook;
 property Hook: IHook read FHook implements IHook;
   public
 constructor Create;
 destructor Destroy; override;
   end;

   constructor TBaseClass.Create;
   begin
 FHook := THook.Create;  // FPC 2.6.4 reports a memory leak here
   end;

   destructor TBaseClass.Destroy;
   begin
 // nothing to do here
   end;


var
   base: IHook;

begin
   base := TBaseClass.Create;
   base.DoIt;
   base := nil; // just to see if it helped with the memory leak - it
doesn't

end.
==[ end ]==


Regards,
  Graeme

--
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http://fpgui.sourceforge.net/

My public PGP key:  http://tinyurl.com/graeme-pgp
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[fpc-pascal] Where and Why is there a memory leak?

2017-09-06 Thread Graeme Geldenhuys 

Hi,

Playing with this small sample application to answer another question in 
this mailing list, I noticed the sample application has a memory leak. 
For the life of me I can't see why or how to resolve it.


I tested with FPC 2.6.4, 3.0.2 and 3.0.4-rc1 under 64-bit FreeBSD.

===[ project1.pas ]
program project1;

{$mode objfpc}{$H+}
{$interfaces COM}

type
  IHook = interface
['{4BCAEDD8-92D8-11E7-88D3-C86000E37EB0}']
procedure DoIt;
  end;

type
  THook = class(TInterfacedObject, IHook)
  private
procedure DoIt;
  end;

  procedure THook.DoIt;
  begin
writeln(ClassName + ' did it');
  end;

type
  TBaseClass = class(TInterfacedObject, IHook)
  private
FHook: IHook;
property Hook: IHook read FHook implements IHook;
  public
constructor Create;
destructor Destroy; override;
  end;

  constructor TBaseClass.Create;
  begin
FHook := THook.Create;  // FPC 2.6.4 reports a memory leak here
  end;

  destructor TBaseClass.Destroy;
  begin
// nothing to do here
  end;


var
  base: IHook;

begin
  base := TBaseClass.Create;
  base.DoIt;
  base := nil; // just to see if it helped with the memory leak - it 
doesn't


end.
==[ end ]==


When I run the program, the output is as follows:

[t1]$ ./project1
THook did it
Heap dump by heaptrc unit
4 memory blocks allocated : 115/120
2 memory blocks freed : 51/56
2 unfreed memory blocks : 64
True heap size : 1114112 (32 used in System startup)
True free heap : 1113696
Should be : 1113760
Call trace for block $00080072F180 size 32
  $00400379 line 35 of project1.lpr
Call trace for block $00080072F0C0 size 32



Personally I always use CORBA style interfaces, never reference counted 
COM style interfaces. So my programs normally don't have this issue, and 
I use interfaces a lot.





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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