[Lazarus] BitBlt caused SIGFPE in lclproc.pas

[xrfang]

Hi There,

Why the following code generated SIGFPE on BitBlt?

===
procedure TForm1.Button1Click(Sender: TObject);
var
  png: TPortableNetworkGraphic;
  ScreenDC, ClipDC: HDC;
  r: TRect;
begin
  r := Rect(0, 0, 300, 200);
  png := TPortableNetworkGraphic.Create;
  ScreenDC := GetDC(0);
  ClipDC := CreateCompatibleDC(ScreenDC);
  BitBlt(ClipDC, 0, 0, r.Right - r.Left, r.Bottom - r.Top, ScreenDC, r.Left, 
r.Top, SRCCOPY);
  png.LoadFromDevice(ClipDC);
  DeleteDC(ClipDC);
  ReleaseDC(0, ScreenDC);
  png.SaveToFile('test.png');
end;
===

I am on Ubuntu GTK2 and hope this code to run cross platform.

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[Lazarus] polymophic function pointers

[xrfang]

Hi,

Is it possible to do the following:

=== example ===

program test;
type

  TMyClass = class
  type
    TDataFilter = function 
  public
    Value : Double;
    Filter: TDataFilter;
    procedure ViewData;
  end;

procedure TMyClass.ViewData;
begin
  if Filter = nil then
    WriteLn(Value)
  else
    WriteLn(Filter(Value));
end;

var
  t : TMyClass;
begin
  t := TMyClass.Create;
  t.Value = 2;
  t.Filter := @sqr;   //this does not work
  t.Filter := @ln;    //this does not work either
  t.ViewData;
  t.Free;
end.
=

The problem is, while assign function pointers to Filter, I would like to make 
it accept all numeric functions.  That is, if I define it to accept Double, it 
should accept Single and Integers, and if I define it to accept Extended, it 
should accept all numbers.

Possible?

Thanks,
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[Lazarus] "default" visibility for class members

[xrfang]

Hi All,

My class looks like this:

TMyClass = class
  FField1: Integer;
private
  FField2: string;
public
  FField3: string;
end;

Question is, is FField1 private or public or protected?  For all lcl classes,
I see a lot of fields above "private", it looks like they are same as "public", 
because I can access them from outside. But why allow them to be put there 
instead of directly under "public"?

Thanks,
Shannon

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Re: [Lazarus] "global" operator overloading

[xrfang]

No, it's not a dilemma, but rather a requirement. Before generics 
specialization, all required operations for given type must be known. This 
is because the symbol table when the generics is parsed must be 
reconstructed when it gets specialized. Think about declaring usual classes 
with the generic parameter replaced with actual type. If at that time, the 
operation < is not yet defined, the code won't compile anyway.

It is a pity. I think if fpc supports class operators, maybe this problem could 
be solved by using class helpers (my purpose is that users of ttreap class does 
not have to modify treap.pas) ? Is that possible in future FPC?

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[Lazarus] "global" operator overloading

[xrfang]

Hi There,

Days ago I posted a message about compiling error related to operator 
overloading. I found the reason now, but don't know how to fix that.  The code 
is:

=

uses Classes, treap;

type
  TSLCounter = specialize TTreap;

operator <(sl1, sl2: TStringList): Boolean;

=

The compiler complains about "<" is not defined for string list.  If I put the 
operator overloading into treap.pas, there is no problem.

Is there anyway to avoid this dilemma?  Because I don't want treap.pas to 
"reversely" rely on a specialized class.

Thanks,
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Re: [Lazarus] operator overloading

[xrfang]

I confirm that it does not work.  Test program below, and the class source is 
attached.


==Test Program===

program test;

{$mode objfpc}{$H+}

uses
  Classes, treap;

type
  TSLCounter = specialize TTreap;

operator <(sl1, sl2: TStringList): Boolean;
begin
  Result := sl1.Text < sl2.Text;
end;

begin
end.

==Error Message==
Options changed, recompiling clean with -B
/home/xrfang/git/fpcollection/src/units/treap.pas(216,10) Error: Operator is 
not overloaded: "TStringList" < "TStringList"
/home/xrfang/git/fpcollection/src/units/treap.pas(218,15) Error: Operator is 
not overloaded: "TStringList" > "TStringList"
test.lpr(19) Fatal: There were 2 errors compiling module, stopping
=

i.e. whether the operator overloading is defined or not, error message is same.

Thanks.

在 日, 2月 24, 2013 at 4:21 下午，leledumbo  写道：
FPC operator overloading doesn't work inside classes, it must be declared 
globally, so method2 should work. What error do you get? What FPC version do 
you use? 



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unit treap;
{$mode objfpc}
interface
type

  { TTreap }

  generic TTreap = class
const
  MAX_PRIORITY = $7FFF;
type
  PNode = ^TNode;
  TNode = record
Key: TKey;
Value: TValue;
Priority: Cardinal;
Left, Right: PNode;
  end;
private
  Altered: Boolean; //for Insert & Delete
  GoOn: Boolean;//for Traverse
  FCount: Integer;
  NullNode, RootNode: PNode;
  function GetCount: Integer;
  function LeftRotate(Node: PNode): PNode;
  function RightRotate(Node: PNode): PNode;
  function InsertNode(Key: TKey; Value: TValue; Node: PNode): PNode;
  function DeleteNode(Key: TKey; Node: PNode): PNode;
  procedure TraverseNode(Node: PNode; dir: Integer);
  procedure ClearNode(Node: PNode);
  function Compare({%H-}Key: TKey; Node: PNode): Integer;
protected
  function Traverse({%H-}Key: TKey; {%H-}Value: TValue): Boolean; virtual;
  procedure OnDispose({%H-}Value: TValue); virtual;
  function OnInsert({%H-}Key: TKey; {%H-}Value: TValue; {%H-}IsNew: Boolean): Boolean; virtual;
public
  property Count: Integer read GetCount;
  function Insert(Key: TKey; Value: TValue): Boolean;
  function Delete(Key: TKey): Boolean;
  function Find(Key: TKey): PNode;
  procedure Clear;
  constructor Create; virtual;
  destructor Destroy; override;
  procedure Walk(dir: Integer = 0); //0=ascending; 1=descending
  end;

implementation

function TTreap.InsertNode(Key: TKey; Value: TValue; Node: PNode): PNode;
begin
  if Node = NullNode then begin
if OnInsert(Key, Value, True) then begin
  New(Node);
  Node^.Key := Key;
  Node^.Value := Value;
  Node^.Priority := Random(MAX_PRIORITY);
  Node^.Left := NullNode;
  Node^.Right := NullNode;
  Altered := True;
  Inc(FCount);
end;
  end else begin
case Compare(Key, Node) of
  0: begin
Altered := Node^.Value <> Value;
if Altered and OnInsert(Key, Value, False) then Node^.Value := Value;
  end;
  1: begin
Node^.Right := InsertNode(Key, Value, Node^.Right);
if Node^.Right^.Priority < Node^.Priority then
  Node := RightRotate(Node);
  end;
  else begin
Node^.Left := InsertNode(Key, Value, Node^.Left);
if Node^.Left^.Priority < Node^.Priority then
  Node := LeftRotate(Node);
  end;
end;
  end;
  Result := Node;
end;

function TTreap.DeleteNode(Key: TKey; Node: PNode): PNode;
begin
  if Node <> NullNode then begin
case Compare(Key, Node) of
  0: begin
if Node^.Left^.Priority < Node^.Right^.Priority then
  Node := LeftRotate(Node)
else
  Node := RightRotate(Node);
if Node <> NullNode then
  Node := DeleteNode(Key, Node)
else begin
  OnDispose(Node^.Left^.Value);
  Dispose(Node^.Left);
  Node^.Left := NullNode;
  Altered := True;
  Dec(FCount);
end;
  end;
  1: Node^.Right := DeleteNode(Key, Node^.Right);
  else Node^.Left := DeleteNode(Key, Node^.Left);
end;
  end;
  Result := Node;
end;

procedure TTreap.TraverseNode(Node: PNode; dir: Integer);
begin
  if (not GoOn) or (Node = NullNode) then Exit;
  if dir = 0 then begin
TraverseNode(Node^.Left, dir);
if GoOn then GoOn := Traverse(Node^.Key, Node^.Value);
TraverseNode(Node^.Right, dir);
  end else begin

Re: [Lazarus] operator overloading

[xrfang]

I will test again tomorrow to find out what's wrong with my code.  For now, one 
more queston:

I noticed that generics does not work without {$mode objfpc}.  I wonder what is 
the default mode without $mode? Why objfpc is not the default mode?

在 日, 2月 24, 2013 at 11:00 下午，Sven Barth  写道：
On 24.02.2013 15:51, Wildfire wrote: 
> *From:* xrfang 
> *Sent:* Sunday, February 24, 2013 7:31 AM 
> *To:* Lazarus@lists.lazarus.freepascal.org 
> 
> *Subject:* [Lazarus] operator overloading 
> > operator < (p1, p2: TPainter) b: Boolean; <—method2 
> Close, but no cigar... 
> operator < (p1, p2: TPainter): Boolean; 

Both variants will work. The variant with "b: Boolean" was originally 
introduced for the non-Object-Pascal modes (fpc, tp), because there you only 
have the name of the procedure/function as a result variable and as operators 
don't have names (in that sense) you can specify the name of the result 
variable. It works in the Object Pascal modes (delphi, objfpc) however as well. 

Regards, 
Sven 


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[Lazarus] operator overloading

[xrfang]

Hi All,

How can I use operator overloading?  I know the syntax, but it simply does not 
compile...  My situation is:

1. I wrote a TTreap generic class, which is a binary tree.
2. TTreap defines a Compare() with involves < and > operation on its keys.
3. I try to specialize it with the following:

===
interface

TPainterManager = class(specialize TTreap)
public
    class operator < (p1, p2: TPainter) b: Boolean; <-- method1
end;

operator < (p1, p2: TPainter) b: Boolean; <-- method2

implementation
..
===

but neither method1 nor method2 compiles.

What is the correct way to write operator overload routines?

Thanks,
Shannon  I --
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[Lazarus] Check if an abstract method is implemented or not

[xrfang]

Hi All,

I wrote a TPainter abstract class, and a TPaintRect class.  In the TPaintRect 
class I have this code:

procedure TPaintRect.OnMouseEnter(Sender: TObject);
var
  i: Integer;
  p: TPainter;
begin
  for i := 0 to painters.Count - 1 do begin
    p := TPainter(painters.Objects[i]);
    try
      p.OnMouseEnter(Sender);
    except on EAbstractError do ; end;
  end;
  if Assigned(FOnMouseEnter) then FOnMouseEnter(Sender);
end;

While running in IDE, the program will crash because OnMouseEnter is abstract.

My problems are:

1) As I already wrapped it with try-except, I hope it won't trigger IDE 
exception. But even I turn off "Notify on Lazarus Exception" in debugger 
options it still pops up, and the popup said RunError(211), NOT EAbstractError. 
 The program runs well outside of IDE.

2) Is there a way to detect if an abstract method is implemented or not, 
without trying to call it and try...except?

Thanks,
Shannon


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[Lazarus] property setter

[xrfang]

Hi all,

Lazarus auto generated the following code for my class:

procedure TPainter.SetFont(AValue: TFont);
begin
  if FFont=AValue then Exit;
  FFont:=AValue;
end;

My question is, why the "if" clause needed? Is there any performance benefits?

Thanks,
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Re: [Lazarus] Dynamic library dependency error

[xrfang]

Hi Howard,

Thanks for your info.  After adding LCLBase to dependencies, I get these errors:

/usr/bin/ld: warning: link.res contains output sections; did you forget -T?
/usr/bin/ld: /home/xrfang/Desktop/paintrect/lib/x86_64-linux/paintrect.o: 
relocation R_X86_64_32S against `_$PAINTRECT$_Ld1' can not be used when making 
a shared object; recompile with -fPIC
/home/xrfang/Desktop/paintrect/lib/x86_64-linux/paintrect.o: 无法读取符号: 错误的值
liboval.lpr(14) Error: Error while linking

where "无法读取符号: 错误的值" means "cannot read symbol: illegal value".

What's wrong here?

Thanks,
Shannon


在 二, 1月 22, 2013 at 10:41 下午，Howard Page-Clark  写道：
On 22/1/13 2:22, xrfang wrote: 

> I try to make a dynamic library and get this error: 
> 
> paintrect.pas(0,0) Fatal: Can not find unit Controls used by paintrect. 
> Check if package LCLBase is in the dependencies. 

You need to add LCLBase as a project dependency. 
Use the Project Inspector's Add button to show the Add to Project dialog. 
Project -> Project Inspector, 
then in the Project Inspector click the middle tab to open the New Requirement 
page, and in the Package Name combo dropdown choose LCLBase from the long list 
presented. 
Then click the [Create New Requirement] button, and you're done - the new 
package requirement will be listed under Required Packages node in the Project 
Inspector.

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[Lazarus] Dynamic library dependency error

[xrfang]

Hi All,

I try to make a dynamic library and get this error:

paintrect.pas(0,0) Fatal: Can not find unit Controls used by paintrect. Check 
if package LCLBase is in the dependencies.

The source code of my library is:

library liboval;

{$mode objfpc}{$H+}

uses
  paintrect, oval;
function GetPainter: TPainter;
begin
end;
exports GetPainter;
begin
end.    

And the used paintrect.pas is attached.

Any hint is greatly appreciated.

Thanks,
Shannonunit paintrect;

{$mode objfpc}{$H+}

interface

uses
  Classes, Controls, ExtCtrls, Graphics, Types, SysUtils, LCLType;
type
  TPainter = class abstract
  public
OnKeyDown: TKeyEvent;
OnKeyUp: TKeyEvent;
OnUTF8KeyPress: TUTF8KeyPressEvent;
OnMouseDown: TMouseEvent;
OnMouseEnter: TNotifyEvent;
OnMouseLeave: TNotifyEvent;
OnMouseMove: TMouseMoveEvent;
OnMouseUp: TMouseEvent;
OnMouseWheel: TMouseWheelEvent;
OnMouseWheelDown: TMouseWheelUpDownEvent;
OnMouseWheelUp: TMouseWheelUpDownEvent;
procedure Paint(Canvas: TCanvas; Rect: TRect); virtual abstract;
  end;
  { TPaintRect }
  TPaintRect = class
  private
align: TAlign;
box: TPaintBox;
_span: Real;
painters: TStringList; //array of TPainter;
prect: TPaintRect;
FOnKeyDown: TKeyEvent;
FOnKeyUp: TKeyEvent;
FOnMouseDown: TMouseEvent;
FOnMouseEnter: TNotifyEvent;
FOnMouseLeave: TNotifyEvent;
FOnMouseMove: TMouseMoveEvent;
FOnMouseUp: TMouseEvent;
FOnMouseWheel: TMouseWheelEvent;
FOnMouseWheelDown: TMouseWheelUpDownEvent;
FOnMouseWheelUp: TMouseWheelUpDownEvent;
FOnPaint: TNotifyEvent;
FOnUTF8KeyPress: TUTF8KeyPressEvent;
function GetRect(Invert: Boolean = False): TRect;
function GetSpan: Real;
procedure SetSpan(AValue: Real);
procedure OnKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
procedure OnKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
procedure OnMouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
procedure OnMouseEnter(Sender: TObject);
procedure OnMouseLeave(Sender: TObject);
procedure OnMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
procedure OnMouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
procedure OnMouseWheel(Sender: TObject; Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
procedure OnMouseWheelDown(Sender: TObject; Shift: TShiftState; MousePos: TPoint; var Handled: Boolean);
procedure OnMouseWheelUp(Sender: TObject; Shift: TShiftState; MousePos: TPoint; var Handled: Boolean);
procedure OnPaint(Sender: TObject);
procedure OnUTF8KeyPress(Sender: TObject; var UTF8Key: TUTF8Char);
procedure Initialize;
  public
property Span: Real read GetSpan write SetSpan;
constructor Create(ABox: TPaintBox; AnAlign: TAlign; ASpan: Real);
constructor Create(ARect: TPaintRect; AnAlign: TAlign; ASpan: Real);
destructor Destroy; override;
procedure AddPainter(AName: string; APainter: TPainter);
  end;

implementation

{ TPaintRect }

function TPaintRect.GetRect(Invert: Boolean): TRect;
var
  pr : TRect;
  function Size: Integer;
  begin
case align of
  alBottom, alTop: Result := pr.Bottom - pr.Top;
  else Result := pr.Right - pr.Left;
end;
if _span < 1 then begin
  Result := Round(_span * Result);
end else begin
  if _span < 0 then
Result := 0
  else if _span < Result then
Result := Trunc(_span);
end;
  end;
begin
  if Assigned(prect) then
pr := prect.GetRect(True)
  else
pr := Rect(0, 0, box.ClientWidth - 1, box.ClientHeight - 1);
  if align in [alNone, alClient, alCustom] then begin
if Invert then
  Result := Rect(0, 0, 0, 0)
else
  Result := pr;
  end else if Invert then begin
case align of
  alBottom: Result := Rect(pr.Left, pr.Top, pr.Right, pr.Bottom-Size);
  alLeft: Result := Rect(pr.Left+Size, pr.Top, pr.Right, pr.Bottom);
  alRight: Result := Rect(pr.Left, pr.Top, pr.Right-Size, pr.Bottom);
  alTop: Result := Rect(pr.Left, pr.Top+Size, pr.Right, pr.Bottom);
end;
  end else begin
case align of
  alBottom: Result := Rect(pr.Left, pr.Bottom-Size+1, pr.Right, pr.Bottom);
  alLeft: Result := Rect(pr.Left, pr.Top, pr.Left+Size-1, pr.Bottom);
  alRight: Result := Rect(pr.Right-Size+1, pr.Top, pr.Right, pr.Bottom);
  alTop: Result := Rect(pr.Left, pr.Top, pr.Right, pr.Top+Size-1);
end;
  end;
end;

function TPaintRect.GetSpan: Real;
begin
  Result := _span;
end;

procedure TPaintRect.SetSpan(AValue: Real);
begin
  _span := AValue;
  box.Invalidate;
end;

procedure TPaintRect.OnKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
var
  i: Integer;
  p: TPainter;
begin
  for i := 0 to painters.Count - 1 do begin
p := TPainter(painters.Objects[i]);
if Assigned(p.OnKeyDown) then p.OnKeyDown(Sender, Key, Shift);
  end;
  if Assigned(FOnKeyDown) then FO

[Lazarus] Initial value for procedure of object

[xrfang]

Hi,

If I define a class like this:

TMyClass = class(TWinControl)
private
    FOnClick: TNotifyEvent;
    ...
end;

What is the initial value of FOnClick?  Do I have to set it to nil explicitly 
in the constructor?

Thanks,
Shannon--
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[Lazarus] Handle user inputs

[xrfang]

Hi,

I want to use TApplicationProperties.OnUserInput to process keyboard/mouse 
events.  But the parameter of this method is a Cardinal.   My questions are:

1) How do I know its event type, such as keydown/keyup/keypress or mouse move 
etc？

2) How do I know the actual key that is pressed, or the X, Y coordinates of the 
mouse?

Thanks,
Shannon--
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[Lazarus] cross-platform way of put pascal class in a dynamic library

[xrfang]

Hi All,

Is there a safe and cross-platform way to put a Lazarus Class into a dynamic 
library?  The description here: 

http://wiki.freepascal.org/shared_library 

seems not complete and / or out-dated?

Thanks,
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Re: [Lazarus] record literal in FPC?

[xrfang]

I don't know if it's related to the fact that TEdit.CaretPos.X (or Y) is read 
only, or as Mattias said, the with syntax cannot work with record anyway... :-)

This should be a problem (if any) with lazarus not fpc.

Shannon

在 三, 1月 9, 2013 at 8:27 下午，Andreas Schneider  写道：
Interesting. IIRC that worked correctly in Delphi 2010 (it's been a while ...). 
This might be a bug in FPC.

The root of the problem is how properties are handled. Afaics however, the use 
of with should cause it to assign the final record afterwards. Apparently it 
doesn't - at least not always. Could be by design, could be a bug. I'll check 
the bug tracker later and may report that. (You can do that yourself, if you 
want, but sooner or later I would like that functionality to work too, so I've 
a personal interest in this and therefore would not mind to report it :-))

Greetings,
Andreas


On 09.01.2013 13:19, xrfang wrote:
Hi Adreas,

I just tried, your method did not work as expected.  It compiled ok, but didn't 
put the cursor at the end of the line as I wanted.  However, assign CaretPos a 
new TPoint worked.

Regards,

在 三, 1月 9, 2013 at 4:47 下午，Andreas Schneider  写道：
Hi,

you could also use the with-statement, that is pretty handy in such cases:

with Edit1.CaretPos do
begin
  X := 0;
  Y := 0;
end;
Best Regards,
Andreas


On 08.01.2013 16:30, xrfang wrote:
Hi, 

Is there "record literal in FPC? e.g. normally, you do:

var
   cp : TPoint;

cp.X := 0;
cp.Y := 0;
Edit1.CaretPos := cp;

I would like to use literal directly, such as:

Edit1.CaretPos := (X: 0, Y: 0); 

But the above syntax is wrong. Is there such thing exists?

Thanks,
Shannon


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Re: [Lazarus] record literal in FPC?

[xrfang]

Hi Adreas,

I just tried, your method did not work as expected.  It compiled ok, but didn't 
put the cursor at the end of the line as I wanted.  However, assign CaretPos a 
new TPoint worked.

Regards,

在 三, 1月 9, 2013 at 4:47 下午，Andreas Schneider  写道：
Hi,

you could also use the with-statement, that is pretty handy in such cases:

with Edit1.CaretPos do
begin
  X := 0;
  Y := 0;
end;
Best Regards,
Andreas


On 08.01.2013 16:30, xrfang wrote:
Hi, 

Is there "record literal in FPC? e.g. normally, you do:

var
   cp : TPoint;

cp.X := 0;
cp.Y := 0;
Edit1.CaretPos := cp;

I would like to use literal directly, such as:

Edit1.CaretPos := (X: 0, Y: 0); 

But the above syntax is wrong. Is there such thing exists?

Thanks,
Shannon


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Re: [Lazarus] record literal in FPC?

[xrfang]

Well, my purpose is to make the source code look comfortable, not how the 
binary code is generated :)

Well, again, I got a good idea from Andreas.

Thanks to all of you.

在 三, 1月 9, 2013 at 7:45 下午，leledumbo  写道：
> As far as I know pascal inline directive only affect the compiler, not how 
you write code. Could you please give an example how inline function helps 
in my question? 

Yes it does, what I mean is to create something that Point() function does 
and using inline directive it's nearly the same as assigning record via 
literal. Well, if you know how it's done by other compilers, record literal 
assignment is actually broken down into field by field assignment. So if you 
make a function that returns the record with given arguments as record 
fields, with inline directive the final code would be the same. Well... 
maybe you'll need some other directives as well, but it's just my thought. I 
never really compare the generated code... 



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Re: [Lazarus] record literal in FPC?

[xrfang]

Thanks, but what I want is to AVOID any kind of declarations. So I will use the 
Point() function suggested by ik.

在 三, 1月 9, 2013 at 12:26 上午，Howard Page-Clark  写道：
On 08/1/13 3:30, xrfang wrote: 

> I would like to use literal directly, such as: 
> 
> Edit1.CaretPos := (X: 0, Y: 0); 

You can use a typed constant thus: 

const Origin: TPoint = (x:0; y:0); 

begin 
.. 
Edit1.CaretPos := Origin; 
.. 


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[Lazarus] record literal in FPC?

[xrfang]

Hi, 

Is there "record literal in FPC? e.g. normally, you do:

var
   cp : TPoint;

cp.X := 0;
cp.Y := 0;
Edit1.CaretPos := cp;

I would like to use literal directly, such as:

Edit1.CaretPos := (X: 0, Y: 0); 

But the above syntax is wrong. Is there such thing exists?

Thanks,
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Re: [Lazarus] Linking dynamic libraries

[xrfang]

It's clear now.  One more question, I just installed liblua5.2-0 and it linked 
happily, what else does the "dev" package offer for development?

Thanks,
Shannon

在 日, 12月 30, 2012 at 11:54 下午，Sven Barth  写道：
On 30.12.2012 16:47, xrfang wrote: 
> Hi All, 
> 
> While I compile my program which uses liblua52.so, Lazarus refuse to 
> compile if it cannot find the so file. But on windows, it compile 
> happily without the DLL file. 
> 
> As far as I understand dynamic link libraries are only required at 
> runtime, why lazarus require it on compilation? 

First you need to understand that libraries can be dynamically linked in two 
ways: 
* at runtime 
* at linktime 

The first case is when you (or e.g. an unit) does a LoadLibrary and manually 
queries for each function it needs (often done by the database units provided 
by Lazarus). The other method is used when you have methods declared with 
"external Bar name Foo". Then the library name and the functions that are 
imported are mentioned in the import section of the resulting executable and 
the OS loader ensures that the libraries are loaded and initialized before the 
main application starts. If such a library is missing at program startup you'll 
get an error message. 

And here is where a difference between Windows and Unix systems lies (Note: 
your lua52 unit uses the second case): on Windows it is enough to know the 
library name and the function name and if the library is missing at link time 
this doesn't matter. On Unix though you must have the library available, 
because the linker needs information that is only provided inside the library 
file itself, because the filename is less important on Unix systems. 

So this is not the fault of Lazarus (or Free Pascal to be more precise, as 
Lazarus is only the IDE which calls FPC), but of the different concepts used on 
Unix. 

Solution: just install the dev package of your distribution and it should work. 

Regards, 
Sven 


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[Lazarus] Linking dynamic libraries

[xrfang]

Hi All,

While I compile my program which uses liblua52.so, Lazarus refuse to compile if 
it cannot find the so file.   But on windows, it compile happily without the 
DLL file.

As far as I understand dynamic link libraries are only required at runtime, why 
lazarus require it on compilation?

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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

Hi Sven,

I think that's the library we are talking about... However, make that call to 
@lr[0] will NOT fix the problem, as I mentioned in previous emails.   To help 
you see what happened, I attach the debug log (from lazarus assembly window) 
again.

Also, it is very strange that my programs act very differently on Linux64 and 
Win32.  On windows, even the "correct" version (which runs well on command 
line) will cause access violation in the IDE!

Thanks!

在 日, 12月 30, 2012 at 9:34 下午，Sven Barth  写道：
On 30.12.2012 05:30, leledumbo wrote: 
> Program received signal SIGSEGV, Segmentation fault. 
> 0xb7e386d2 in ?? () from /lib/i386-linux-gnu/libc.so.6 
> (gdb) bt 
> #0 0xb7e386d2 in ?? () from /lib/i386-linux-gnu/libc.so.6 
> #1 0xb7fa2d12 in ?? () from /usr/lib/i386-linux-gnu/liblua5.2.so.0 
> #2 0xb7f95f09 in lua_setfield () from 
> /usr/lib/i386-linux-gnu/liblua5.2.so.0 
> #3 0xb7fa9a9a in luaL_setfuncs () from 
> /usr/lib/i386-linux-gnu/liblua5.2.so.0 
> #4 0x08066821 in LUAL_SETFUNCS (L=0x8071008, LR=..., highLR=1, NUP=0) at 
> lua52.pas:835 
> #5 0x080669e4 in LUAL_NEWLIB (L=0x8071008, LR=..., highLR=1) at 
> lua52.pas:859 
> #6 0x0804a3ea in main () at test.pas:31 
> 
> As you can see, the pointer changes when you pass an open array into another 
> function expecting open array, even when static array is used (I've tried 
> that one too). So, somebody with enough compiler knowledge should analyze 
> this. Maybe you should create a bug report. 

If the code of that lua52.pas is the one available here: 
http://lua-users.org/files/wiki_insecure/lua52.pas the error is understandable 
if one looks at the luaL_newlib function (the array overload): 

=== source begin === 

procedure luaL_newlib(L: Plua_State; lr: array of luaL_Reg); 
begin 
luaL_newlibtable(L, lr); 
luaL_setfuncs(L, @lr, 0); 
end; 

=== source end === 

The address of the open array parameter is passed, not the array to the first 
element. If you change the luaL_setfuncs call to 

=== source begin === 

luaL_setfuncs(L, @lr[0], 0); 

=== source end === 

it should work... 

Regards, 
Sven 

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== CASE 1: SIGSEGV @ callq 0x4e01d8 
==
procedure luaL_newlib(L: Plua_State; lr: array of luaL_Reg);
begin
856   luaL_newlibtable(L, lr);
857   luaL_setfuncs(L, @lr, 0);
  //luaL_setfuncs(L, lr, 0);
859 end;
--
lua52.pas:856   luaL_newlibtable(L, lr);
4E0364 488b55e8 mov-0x18(%rbp),%rdx
4E0368 488b75f0 mov-0x10(%rbp),%rsi
4E036C 488b7df8 mov-0x8(%rbp),%rdi
4E0370 e8e3fe   callq  0x4e0258 
lua52.pas:857   luaL_setfuncs(L, @lr, 0);
4E0375 488b75f0 mov-0x10(%rbp),%rsi
4E0379 488b7df8 mov-0x8(%rbp),%rdi
4E037D ba   mov$0x0,%edx
4E0382 e851fe   callq  0x4e01d8 
  <--
lua52.pas:859   end;

== CASE 2: SIGSEGV @ callq 0x4e01d8 
==
procedure luaL_newlib(L: Plua_State; lr: array of luaL_Reg);
begin
856   luaL_newlibtable(L, lr);
857   luaL_setfuncs(L, @lr[0], 0);
  //luaL_setfuncs(L, lr, 0);
859 end;
--
lua52.pas:856   luaL_newlibtable(L, lr);
4E0364 488b55e8 mov-0x18(%rbp),%rdx
4E0368 488b75f0 mov-0x10(%rbp),%rsi
4E036C 488b7df8 mov-0x8(%rbp),%rdi
4E0370 e8e3fe   callq  0x4e0258 
lua52.pas:857   luaL_setfuncs(L, @lr[0], 0);
4E0375 488b75f0 mov-0x10(%rbp),%rsi
4E0379 488b7df8 mov-0x8(%rbp),%rdi
4E037D ba   mov$0x0,%edx
4E0382 e851fe   callq  0x4e01d8 
  <--
lua52.pas:859   end;

== CASE 3: NO ERROR 
==
procedure luaL_newlib(L: Plua_State; lr: array of luaL_Reg);
begin
856   luaL_newlibtable(L, lr);
  // luaL_setfuncs(L, @lr, 0);
858   luaL_setfuncs(L, lr, 0);
859 end;
--
lua52.pas:856   luaL_newlibtable(L, lr);
4E0364 488b55e8 mov-0x18(%rbp),%rdx
4E0368 488b75f0 mov-0x10(%rbp),%rsi
4E036C 488b7df8 mov-0x8(%rbp),%rdi
4E0370 e8e3fe   callq  0x4e0258 
lua52.pas:858   luaL_setfuncs(L, lr, 0);
4E0375 488b55e8 mov-0x18(%rbp),%rdx
4E0379 488b75f0 mov-0x10(%rbp),%rsi
4E037D 488b7df8 mov-0x8(%rbp),%rdi
4E0381 b9   mov$0x0,%ecx
4E0386 e855fe   callq  0x4e01e0 
lua52.pas:859   end;
-

Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

Hi leledumbo,

Apparently, I've been wrong for all these years using Delphi :-S.   I always 
think that open arrays are same as dynamic arrays. So,

1) from the source code of lua52.pas, how do you know the array parameter to 
luaL_newlib() accepts only static array but not dynamic array?   If you don't 
read the source code or document of lua API?

2) If the api only accept static array but I passed dynamic array and hence it 
crashed, then it is my fault, not FPC compilers.   In such case, shall I still 
file a bug report?

3) Finally, if I still file a bug, can I just ask the reviewer to read this 
mail thread as it is archived?

Thanks

在 日, 12月 30, 2012 at 7:41 下午，leledumbo  写道：
> 1) what's the difference between open array and dynamic array? Is "array of 
Integer" open or dynamic? 

Open array can only be declared as parameter type, it can't be declared as a 
variable type. When done in latter case, it will always be dynamic array. 
The following example will explain: 

type 
TDynIntArray = array of Integer; 

procedure p1(a: TDynIntArray); // here a is dynamic array 
procedure p2(a: array of Integer); // here a is open array 

a good article explaining open array: 
http://rvelthuis.de/articles/articles-openarr.html 
so "array of Integer" can mean both, depending where and how it's declared. 

> 2) How to report a bug, and I believe this maybe a bug in the fpc 
> compiler? 

http://wiki.lazarus.freepascal.org/How_do_I_create_a_bug_report 

or just go to bugs.freepascal.org, login (create account if you don't have 
one) and press report issue (the fields are mostly intuitive). 



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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

Hi leledumbo,

I have a few questions:

1) what's the difference between open array and dynamic array? Is "array of 
Integer" open or dynamic?

2) How to report a bug, and I believe this maybe a bug in the fpc compiler?

Thanks

在 日, 12月 30, 2012 at 12:30 下午，leledumbo  写道：
Sorry, I think I was too fast in reading the unit. After reading slowly, the 
APIs actually uses open array, not dynamic array. In this case @lib should 
be the same as @lib[0], but here's something interesting: I tried your code 
(converted as program): 

uses 
lua52; 
type 
TluaLReg = array of luaL_Reg; 
var 
LUA: Plua_State; 
lib : array of luaL_Reg; 
//lib : PluaL_Reg; 
i: Integer; 

function l_dat_upd(LUA: Plua_State): LongInt; cdecl; 
begin 
end; 

function l_dat_clr(LUA: Plua_State): LongInt; cdecl; 
begin 
end; 

begin 
LUA := luaL_newstate(); 
luaL_openlibs(LUA); 
SetLength(lib, 2); 
//SetLength(TluaLReg(lib), 2); 
lib[0].name := 'update'; 
lib[0].func := @l_dat_upd; 
lib[1].name := 'clear'; 
lib[1].func := @l_dat_clr; 
writeln('actual = $'+HexStr(ptruint(@lib),8)); 
luaL_newlib(LUA, lib); 
lua_setglobal(LUA, 'data'); 
lua_close(LUA); 
end. 

inserting some writelns in lua52 unit near problematic functions and running 
in gdb results in: 

luaL_newlib oa = $BFFFEE30 
luaL_setfuncs oa = $BFFFECC0 

Program received signal SIGSEGV, Segmentation fault. 
0xb7e386d2 in ?? () from /lib/i386-linux-gnu/libc.so.6 
(gdb) bt 
#0 0xb7e386d2 in ?? () from /lib/i386-linux-gnu/libc.so.6 
#1 0xb7fa2d12 in ?? () from /usr/lib/i386-linux-gnu/liblua5.2.so.0 
#2 0xb7f95f09 in lua_setfield () from 
/usr/lib/i386-linux-gnu/liblua5.2.so.0 
#3 0xb7fa9a9a in luaL_setfuncs () from 
/usr/lib/i386-linux-gnu/liblua5.2.so.0 
#4 0x08066821 in LUAL_SETFUNCS (L=0x8071008, LR=..., highLR=1, NUP=0) at 
lua52.pas:835 
#5 0x080669e4 in LUAL_NEWLIB (L=0x8071008, LR=..., highLR=1) at 
lua52.pas:859 
#6 0x0804a3ea in main () at test.pas:31 

As you can see, the pointer changes when you pass an open array into another 
function expecting open array, even when static array is used (I've tried 
that one too). So, somebody with enough compiler knowledge should analyze 
this. Maybe you should create a bug report. 



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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

The end of array mark is added by lua52.pas, if you read the source code...  My 
problem is solved if I remove the overloaded luaL_newlib function and use only 
the original pointer version, i.e.

var lib: array of luaL_Reg;
luaL_newlib(L, PluaL_Reg(lib));

It seems that while converting from dynamic array to pointer, the compiler 
knows to point to the first element of the array, not the structure.  Could 
anyone confirm this behavior?

The remaining problems are: 1) why the lupas program works well even with the 
problematic overloaded version?  I tested on Windows 7 (32bit), both programs 
failed.  2) I will email the author of lua52.pas to investigate the overloaded 
functions, and personally I will suggest to not use overloading at all.

Shannon

在 六, 12月 29, 2012 at 9:39 下午，leledumbo  写道：
Reading luaL_newlib documentation and lua52.pas implementation of it (it's a 
macro in the original C code), I see that you need a sentinel value to mark 
the end of the array by putting nil in the name part. I was already skeptic 
since the API doesn't mention the number of elements in the array as 
commonly required by a C function. 



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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

PluaL_Reg is defined by lua52.pas.   In the email I omitted irrelevant code, 
but full source is attached in the first email. 

在 六, 12月 29, 2012 at 3:13 下午，Flávio Etrusco  写道：
Your code sample doesn't have a declaration for PluaL_Reg (and you 
don't use the TluaLReg type). Was it a simple copy'n'paste error or is 
it declared by the Lua wrapper? 

On Sat, Dec 29, 2012 at 4:00 AM, xrfang wrote: 
> Sorry, we are talking about same thing. In my program I am using dynamic 
> array, NOT static, but the assembly is same. In leledumbo's example, the 
> assembly is differnt. 
> 
> 在 六, 12月 29, 2012 at 2:55 下午，Hans-Peter Diettrich 写道： 
> 
> leledumbo schrieb: 
>>> The Assembler shows that @lib and @lib[0] are exactly same thing. 
> 
> That's true for static arrays. 
> 
>> The following program shows that they are NOT the same 
> 
> That's true for dynamic (managed) arrays. 
> 
> You're talking about different array types. 
> 
> DoDi 
> 
> 
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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

Sorry, we are talking about same thing. In my program I am using dynamic array, 
NOT static, but the assembly is same. In leledumbo's example, the assembly is 
differnt.

在 六, 12月 29, 2012 at 2:55 下午，Hans-Peter Diettrich  写道：
leledumbo schrieb: 
>> The Assembler shows that @lib and @lib[0] are exactly same thing. 

That's true for static arrays. 

> The following program shows that they are NOT the same 

That's true for dynamic (managed) arrays. 

You're talking about different array types. 

DoDi 


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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

Hi leledumbo,

You are right that they are not same:

begin
  setlength(a1,1);
  a1[0] := 12345;
  getvalue(@a1);
  getvalue(@a1[0]);
end.  

The assembly code for the 2 getvalue() are:

project1.lpr:14 getvalue(@a1);
0040022F 48bf40a26200 movabs $0x62a240,%rdi
00400239 e862ff           callq 0x4001a0 
project1.lpr:15 getvalue(@a1[0]);
0040023E 488b3c2540a26200     mov 0x62a240,%rdi
00400246 e855ff           callq 0x4001a0 

One used movabs, and the other use mov.  But why the generated assembly in my 
code are same?

Shannon


在 六, 12月 29, 2012 at 1:26 下午，leledumbo  写道：
> The Assembler shows that @lib and @lib[0] are exactly same thing. 

The following program shows that they are NOT the same 

#!/usr/bin/instantfpc 
var 
a1: array of Integer; 
begin 
setlength(a1,1); 
writeln(ptruint(@a1)); 
writeln(ptruint(@a1[0])); 
end. 

output: 
$ chmod +x test.pas 
$ ./test.pas 
134651632 
3077795880 



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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

Please see attached log file I copied from the assembler window.  I am yet to 
test this on windows.

Thanks,
Shannon

在 六, 12月 29, 2012 at 1:26 下午，leledumbo  写道：
> The Assembler shows that @lib and @lib[0] are exactly same thing. 

The following program shows that they are NOT the same 

#!/usr/bin/instantfpc 
var 
a1: array of Integer; 
begin 
setlength(a1,1); 
writeln(ptruint(@a1)); 
writeln(ptruint(@a1[0])); 
end. 

output: 
$ chmod +x test.pas 
$ ./test.pas 
134651632 
3077795880 



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== CASE 1: SIGSEGV @ callq 0x4e01d8 
==
procedure luaL_newlib(L: Plua_State; lr: array of luaL_Reg);
begin
856   luaL_newlibtable(L, lr);
857   luaL_setfuncs(L, @lr, 0);
  //luaL_setfuncs(L, lr, 0);
859 end;
--
lua52.pas:856   luaL_newlibtable(L, lr);
4E0364 488b55e8 mov-0x18(%rbp),%rdx
4E0368 488b75f0 mov-0x10(%rbp),%rsi
4E036C 488b7df8 mov-0x8(%rbp),%rdi
4E0370 e8e3fe   callq  0x4e0258 
lua52.pas:857   luaL_setfuncs(L, @lr, 0);
4E0375 488b75f0 mov-0x10(%rbp),%rsi
4E0379 488b7df8 mov-0x8(%rbp),%rdi
4E037D ba   mov$0x0,%edx
4E0382 e851fe   callq  0x4e01d8 
  <--
lua52.pas:859   end;

== CASE 2: SIGSEGV @ callq 0x4e01d8 
==
procedure luaL_newlib(L: Plua_State; lr: array of luaL_Reg);
begin
856   luaL_newlibtable(L, lr);
857   luaL_setfuncs(L, @lr[0], 0);
  //luaL_setfuncs(L, lr, 0);
859 end;
--
lua52.pas:856   luaL_newlibtable(L, lr);
4E0364 488b55e8 mov-0x18(%rbp),%rdx
4E0368 488b75f0 mov-0x10(%rbp),%rsi
4E036C 488b7df8 mov-0x8(%rbp),%rdi
4E0370 e8e3fe   callq  0x4e0258 
lua52.pas:857   luaL_setfuncs(L, @lr[0], 0);
4E0375 488b75f0 mov-0x10(%rbp),%rsi
4E0379 488b7df8 mov-0x8(%rbp),%rdi
4E037D ba   mov$0x0,%edx
4E0382 e851fe   callq  0x4e01d8 
  <--
lua52.pas:859   end;

== CASE 3: NO ERROR 
==
procedure luaL_newlib(L: Plua_State; lr: array of luaL_Reg);
begin
856   luaL_newlibtable(L, lr);
  // luaL_setfuncs(L, @lr, 0);
858   luaL_setfuncs(L, lr, 0);
859 end;
--
lua52.pas:856   luaL_newlibtable(L, lr);
4E0364 488b55e8 mov-0x18(%rbp),%rdx
4E0368 488b75f0 mov-0x10(%rbp),%rsi
4E036C 488b7df8 mov-0x8(%rbp),%rdi
4E0370 e8e3fe   callq  0x4e0258 
lua52.pas:858   luaL_setfuncs(L, lr, 0);
4E0375 488b55e8 mov-0x18(%rbp),%rdx
4E0379 488b75f0 mov-0x10(%rbp),%rsi
4E037D 488b7df8 mov-0x8(%rbp),%rdi
4E0381 b9   mov$0x0,%ecx
4E0386 e855fe   callq  0x4e01e0 
lua52.pas:859   end;
--
830 procedure luaL_setfuncs(L: Plua_State; lr: PluaL_Reg; nup: Integer); cdecl; 
external LUA_LIB_NAME;

procedure luaL_setfuncs(L: Plua_State; lr: array of luaL_Reg; nup: Integer);
begin
834   luaL_setfuncs(L, @lr, nup);
835 end;
--
lua52.pas:834   luaL_setfuncs(L, @lr, nup);
4E022F 488b75f0 mov-0x10(%rbp),%rsi
4E0233 8b55e8   mov-0x18(%rbp),%edx
4E0236 488b7df8 mov-0x8(%rbp),%rdi
4E023A e899ff   callq  0x4e01d8 

lua52.pas:835   end;

==

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Re: [Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

The Assembler shows that @lib and @lib[0] are exactly same thing.   The problem
is in lua52.pas, which I am still tracing.  Now the most strange thing is why 
one of my two programs caused SIGSEGV while another one using same code block 
does not?  Is it because one of them is gui program and the other is cli?

I will post a debug report of assembly call points for these 2 programs on both 
Linux-64 and Win-32 platforms.

Thanks,
Shannon

在 六, 12月 29, 2012 at 12:26 上午，leledumbo  写道：
Pointer and dynamic array are not the same, even though dynamic array is 
built on top of pointer (to a structure). When you pass a dynamic array 
variable, you're passing pointer TO THE STRUCTURE, NOT THE DATA. To 
correctly do it, you have to pass pointer to the first data, which is 
@lib[0] in your case. 



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[Lazarus] SEGFAULT: difference between pointer and dynarray?

[xrfang]

Hi All,

I encountered a strange problem with lua integration.  Following is the 
problematic part (full source attached):

type
  TluaLReg = array of luaL_Reg;
var
  LUA: Plua_State;
  lib : array of luaL_Reg;
  //lib : PluaL_Reg;
  i: Integer;
implementation
//omitted, see attached source...
initialization
LUA := luaL_newstate();
luaL_openlibs(LUA);
SetLength(lib, 2);
//SetLength(TluaLReg(lib), 2);
lib[0].name := 'update';
lib[0].func := @l_dat_upd;
lib[1].name := 'clear';
lib[1].func := @l_dat_clr;
luaL_newlib(LUA, lib);      <--Access Violation Here
lua_setglobal(LUA, 'data');
finalization
lua_close(LUA);
end.
                              
The above code caused access violation, unless I use the commented blue code to 
replace the red code.  I wonder what's the difference between PluaL_Reg and 
array of luaL_Reg??  What's more strange is that the same code is OK after I 
copied it to a separate console mode application.  In the attached archive, 
there are both the problematic project and the OK project.

In LUA manual about luaL_newlib(), it said, the 2nd parameter (lib) must be an 
array not pointer to an array.   I am confused what happened here and further 
more, what's the underlying structure of a normal array in FP (If I am correct, 
dynamic array is same as pointer, at least that's what I learned in Delphi).

My environment is 64 bit Linux 3.5.0 (Mint 14).

Thanks a lot.

Sincerely,
Shannon



luaintf.tar.gz
Description: application/compressed-tar
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Re: [Lazarus] Traverse a TFPDataHashTable

[xrfang]

Cool,  btw, what is the release plan for 2.6.2 and 2.6.4 ?

在 五, 12月 28, 2012 at 7:36 下午，Sven Barth  写道：
On 28.12.2012 12:22, xrfang wrote: 
> Hi, 
> 
> How can I traverse a TFPDataHashTable? The ForEachCall method is 
> protected. Do I have to write a sub-class to expose this method? 
> 
> The requirement is that I use it to organize a bunch of objects, and 
> need to free the memory of these objects. 

Around two weeks ago a public call "Iterate" was added to "TFPDataHashTable" in 
trunk. If you use 2.6.0 or the to-be-released 2.6.2 you'll need to either 
sub-class the type or use a class helper... 

Regards, 
Sven 


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[Lazarus] Traverse a TFPDataHashTable

[xrfang]

Hi,

How can I traverse a TFPDataHashTable?  The ForEachCall method is protected.  
Do I have to write a sub-class to expose this method? 

The requirement is that I use it to organize a bunch of objects, and need to 
free the memory of these objects.

Thanks,
Shannon--
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Re: [Lazarus] Is it possible to detect type in a generic class

[xrfang]

Thanks a lot for the code sample.   TypeInfo will be useful, but for now I give 
up this route, because I hope it to be more "elastic" by providing an Append() 
method
if T is an array of something, otherwise no Append() method, this seems can 
only be achieved by inheritance instead of generics.

在 五, 12月 28, 2012 at 7:11 下午，Sven Barth  写道：
On 28.12.2012 00:58, xrfang wrote: 
> Hi, 
> 
> Suppose I have a generic class like this: 
> 
> type 
> TSerie = generic class 
> public 
> procedure Append(value: T); 
> end 

It should be "generic TSerie = class". 

> 
> then, in the Append procedure can I do something like: 
> 
> case *typeof*(T) of 
> integer: // do something with integer 
> string: // do someting with string 
> ... ... 
> end; 

Don't use "TypeOf". The function you are looking for is called "TypeInfo" and 
works with every type, except Enums with jumps (e.g. TTestEnum = (teOne := 1, 
teTwo := 5)). 

Here you have an example: 

=== source begin === 

program tgentypes; 

{$mode objfpc} 

uses 
typinfo; 

type 
generic TTest = class 
class procedure DoSomething(aArg: T); 
end; 

{ TTestClass } 

class procedure TTest.DoSomething(aArg: T); 
var 
ti: PTypeInfo; 
begin 
ti := TypeInfo(aArg); 
case ti^.Kind of 
tkInteger: 
Writeln('Type is an integer'); 
tkAString: 
Writeln('Type is an AnsiString'); 
tkUString: 
Writeln('Type is a UnicodeString'); 
tkBool: 
Writeln('Type is a Boolean'); 
tkEnumeration: 
Writeln('Type is an enumeration'); 
tkSString: 
Writeln('Type is a ShortString'); 
tkClass: 
Writeln('Type is a class'); 
tkObject: 
Writeln('Type is an object'); 
else 
Writeln('Unhandled type: ', ti^.Kind); 
end; 
end; 

type 
TTestEnum = (teOne, teTwo, teThree); 
TTestObject = object 

end; 

TTestLongInt = specialize TTest; 
TTestAnsiString = specialize TTest; 
TTestUnicodeString = specialize TTest; 
TTestShortString = specialize TTest; 
TTestBoolean = specialize TTest; 
TTestTTestEnum = specialize TTest; 
TTestTObject = specialize TTest; 
TTestTTestObject = specialize TTest; 

var 
obj: TObject; 
testobj: TTestObject; 
begin 
TTestLongInt.DoSomething(42); 
TTestAnsiString.DoSomething('Hello World'); 
TTestUnicodeString.DoSomething('Hello World'); 
TTestShortString.DoSomething('Hello World'); 
TTestBoolean.DoSomething(True); 
TTestTTestEnum.DoSomething(teOne); 
TTestTObject.DoSomething(obj); 
TTestTTestObject.DoSomething(testobj); 
end. 

=== source end === 

For getting the exact value of the argument you need to rely on the information 
provided by the RTTI as you can't use e.g. "IntToStr(aArg)" in case of an 
integer as you'll get a compiler error when you specialize the class with 
something that is not an Integer. 

Regards, 
Sven 


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[Lazarus] Is it possible to detect type in a generic class

[xrfang]

Hi,

Suppose I have a generic class like this:

type 
  TSerie = generic class
  public
    procedure Append(value: T);   
  end

then, in the Append procedure can I do something like:

case typeof(T) of
  integer: // do something with integer
  string: // do someting with string
  ... ...
end;

Thanks!
Shannon--
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