Delphi 12 und SendMessage

[EscapedFromMatrix]

Da gibt es Abweichungen.


showmessage(inttostr(sizeof(aCopyData)));

D11
x64=24
x86=12

D12
x64=8
x86=4

[EscapedFromMatrix]

Ich mache noch weitere Tests, aber so scheint es zu klappen:
SendMessage(hTargetWnd, WM_COPYDATA, NativeUInt(Handle), NativeInt(@aCopyData));

[DeddyH]

Und so?
SendMessage(hTargetWnd, WM_COPYDATA, wParam(Handle), lParam(@aCopyData));

[EscapedFromMatrix]

Das klappt auch.
Wenn man die Definitionen für wParam und lParam verfolgt, landet man ja letztendlich bei NativeUInt und NativeInt.

[himitsu]

Das im Post #5 (für D12) kann eigentlich nicht stimmen.
Wie ist denn TCopyDataStruct deklariert? (Strg+Linkklick aka "Deklaration suchen")

[Kas Ob.]

Zitat von EscapedFromMatrix:

Da gibt es Abweichungen.

showmessage(inttostr(sizeof(aCopyData)));

D11
x64=24
x86=12

D12
x64=8
x86=4

That can't be right.

First i put SizeOf(TCopyDataStruct) not sizeof(aCopyData), why it is important because 8 and 4 are the size of single and simple pointer, not a record (struct), and 8 and 4 looks like a pointer something like PCopyDataStruct not TCopyDataStruct, or you just used @aCopyData by mistake.
Second as rule of thumb, never ever use with SendMessage, PostMessage... parameters other than WPARAM and LPARAM, or just cast them.

[EscapedFromMatrix]

[QUOTE=Kas Ob.;1533652]

Zitat von EscapedFromMatrix:

First i put SizeOf(TCopyDataStruct) not sizeof(aCopyData)...

Sorry, my mistake:

showmessage(inttostr(sizeof(TCopyDataStruct)));
D11, x86= 12
D11, x64= 24

D12, x86= 12
D12, x64= 24

[himitsu]

SizeOf(Variable) ist nicht falsch.
Der Typ und die Variable müssten sowieso gleich groß sein, da die Variable ja den "selben" Typ hätte.

Das sieht mehr wie ein Pointer aus (4 Byte = 32 Bit und 8 Byte = 64 Bit)
z.B. PCopyDataStruct statt TCopyDataStruct
aber auch da wären SizeOf(PCopyDataStruct) und SizeOf(Variable) // var Variable: PCopyDataStruct; gleich.

[Kas Ob.]

Zitat von himitsu:

SizeOf(Variable) ist nicht falsch.
Der Typ und die Variable müssten sowieso gleich groß sein, da die Variable ja den "selben" Typ hätte.

Das sieht mehr wie ein Pointer aus (4 Byte = 32 Bit und 8 Byte = 64 Bit)
z.B. PCopyDataStruct statt TCopyDataStruct
aber auch da wären SizeOf(PCopyDataStruct) und SizeOf(Variable) // var Variable: PCopyDataStruct; gleich.

You are right, but for best practice i prefer never to use variable, to avoid situations like the following

Code:

type
  PMyRecord = ^TMyRecord;

  TMyRecord = record
    Buffer: array[0..31] of Byte;
  end;

  TMyClass = class
  public
    Rec1: TMyRecord;
    Rec2: PMyRecord;
  end;
var
  C:TMyClass;
begin
  Writeln(IntToStr(SizeOf(C.Rec1)));   // 32 
  Writeln(IntToStr(SizeOf(C.Rec2)));   // 4 on 32bit, 8 on 64bit
  Readln;
end.

This thing will be dangerous or more impactful when TMyRecord is small like 4 or 8 and pass on one platform to fail on the other, can happen when updating legacy code or just redesigning data structures.

[dummzeuch]

Zitat von Kas Ob.:

You are right, but for best practice i prefer never to use variable, to avoid situations like the following

Code:

type
  PMyRecord = ^TMyRecord;

  TMyRecord = record
    Buffer: array[0..31] of Byte;
  end;

  TMyClass = class
  public
    Rec1: TMyRecord;
    Rec2: PMyRecord;
  end;
var
  C:TMyClass;
begin
  Writeln(IntToStr(SizeOf(C.Rec1)));   // 32 
  Writeln(IntToStr(SizeOf(C.Rec2)));   // 4 on 32bit, 8 on 64bit
  Readln;
end.

This thing will be dangerous or more impactful when TMyRecord is small like 4 or 8 and pass on one platform to fail on the other, can happen when updating legacy code or just redesigning data structures.

Unfortunately that opens the possibility for a different kind of error:
You check the size of the type you are using at some time and later on change the variable declaration to a different type. SizeOf(VariableName) will then automatically reflect that change while SizOf(TOldType) will still return the size of the original type. If you don't catch that, your code will be wrong. That's the reason I prefer using the variable instead of the type.