Re: [fpc-pascal] Error: Can't take the address of constant expressions

2012-09-26 Thread Jonas Maebe 

On 26 Sep 2012, at 07:58, Vincent Snijders wrote:

> 2012/9/25 Bernd :
>> 2012/9/25 patspiper :
>>> procedure test;
>>> begin
>>>  Move(MyClass1.Ref.Data^, MyClass2.Ref.Data^, 1);
>>> end;
>> 
>> and if you cast it to some other pointer type before dereferencing the
>> error goes away:
>> 
>> procedure test;
>> begin
>>  Move(MyClass1.Ref.Data^, PByte(MyClass2.Ref.Data)^, 1);
>> end;
>> 
>> But this should not be necessary.
> 
> Why not?  The error is correct. By using the type cast you tell the
> compiler you know what you are doing and that is should not bother
> doing the sanity check.

If that were true, then using a local variable that is an untyped pointer would 
also have to fail. It is in fact a compiler bug.


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Re: [fpc-pascal] Error: Can't take the address of constant expressions

2012-09-26 Thread patspiper 

On 26/09/12 08:58, Vincent Snijders wrote:

2012/9/25 Bernd:

2012/9/25 patspiper:

procedure test;
begin
   Move(MyClass1.Ref.Data^, MyClass2.Ref.Data^, 1);
end;

and if you cast it to some other pointer type before dereferencing the
error goes away:

procedure test;
begin
   Move(MyClass1.Ref.Data^, PByte(MyClass2.Ref.Data)^, 1);
end;

But this should not be necessary.

Why not?  The error is correct. By using the type cast you tell the
compiler you know what you are doing and that is should not bother
doing the sanity check.

So IMO, not a bug.

Can anybody test under Delphi? The complete unit is in the OP.

Stephano


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Re: [fpc-pascal] Error: Can't take the address of constant expressions

2012-09-25 Thread Vincent Snijders 
2012/9/25 Bernd :
> 2012/9/25 patspiper :
>> procedure test;
>> begin
>>   Move(MyClass1.Ref.Data^, MyClass2.Ref.Data^, 1);
>> end;
>
> and if you cast it to some other pointer type before dereferencing the
> error goes away:
>
> procedure test;
> begin
>   Move(MyClass1.Ref.Data^, PByte(MyClass2.Ref.Data)^, 1);
> end;
>
> But this should not be necessary.

Why not?  The error is correct. By using the type cast you tell the
compiler you know what you are doing and that is should not bother
doing the sanity check.

So IMO, not a bug.

Vincent
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Re: [fpc-pascal] Error: Can't take the address of constant expressions

2012-09-25 Thread patspiper 

On 25/09/12 20:43, Bernd wrote:

2012/9/25 patspiper :

procedure test;
begin
   Move(MyClass1.Ref.Data^, MyClass2.Ref.Data^, 1);
end;

and if you cast it to some other pointer type before dereferencing the
error goes away:

procedure test;
begin
   Move(MyClass1.Ref.Data^, PByte(MyClass2.Ref.Data)^, 1);
end;

But this should not be necessary.

Thanks for the feedback. Submitted as:
http://bugs.freepascal.org/view.php?id=22979

Stephano
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Re: [fpc-pascal] Error: Can't take the address of constant expressions

2012-09-25 Thread Bernd 
2012/9/25 patspiper :
> procedure test;
> begin
>   Move(MyClass1.Ref.Data^, MyClass2.Ref.Data^, 1);
> end;

and if you cast it to some other pointer type before dereferencing the
error goes away:

procedure test;
begin
  Move(MyClass1.Ref.Data^, PByte(MyClass2.Ref.Data)^, 1);
end;

But this should not be necessary.
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Re: [fpc-pascal] Error: Can't take the address of constant expressions

2012-09-25 Thread Bernd 
2012/9/25 patspiper :
> Hi,
>
> Despite
> http://wiki.freepascal.org/User_Changes_2.4.0#Treating_direct-mapped_properties_as_regular_fields,
> shouldn't the following be legal? I tested under FPC 2.6.1 and 2.7.1.

This shouldn't even matter here since IMHO it should work even if Ref
were a function (and it works if Ref is a function), it should always
work as long as the expression before the ^ is a pointer type.

And interestingly this works also (as it should):

type
  TMyClass = class
  private
FRef: Pointer;
  public
property Ref: Pointer read FRef write FRef;
  end;

var
  MyClass1, MyClass2: TMyClass;

procedure test;
begin
  Move(MyClass1.Ref^, MyClass2.Ref^, 1);
end;

but

Move(MyClass1.Ref, MyClass2.Ref, SizeOf(TMyClass.Ref));

will give an error (as it should), no matter how its internally
represented because the code that is using this property should not be
expected to make assumptions about internal compiler optimizations, it
should always treat it like a property.

But your example should work, IMHO you have found a bug.
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[fpc-pascal] Error: Can't take the address of constant expressions

2012-09-25 Thread patspiper 

Hi,

Despite 
http://wiki.freepascal.org/User_Changes_2.4.0#Treating_direct-mapped_properties_as_regular_fields, 
shouldn't the following be legal? I tested under FPC 2.6.1 and 2.7.1.


  TMyRecord = record
Data: pointer;
  end;

  TMyClass = class
  private
FRef: TMyRecord;
  public
property Ref: TMyRecord read FRef write FRef;
  end;

var
  MyClass1, MyClass2: TMyClass;

procedure test;
begin
  Move(MyClass1.Ref.Data^, MyClass2.Ref.Data^, 1);
end;

The complete program is attached.

Thanks,
Stephano
program constaddresstest;

{$IFDEF FPC}
{$mode delphi}
{$ENDIF}
{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes
  { you can add units after this };

type

  TMyRecord = record
Data: pointer;
  end;

  TMyClass = class
  private
FRef: TMyRecord;
  public
property Ref: TMyRecord read FRef write FRef;
  end;

var
  MyClass1, MyClass2: TMyClass;

procedure test;
begin
  Move(MyClass1.Ref.Data^, MyClass2.Ref.Data^, 1);
end;

begin
end.

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Re: [fpc-pascal] Error: Can't take the address of constant expressions

2011-02-21 Thread Jonas Maebe 

On 21 Feb 2011, at 16:59, Roland Turcan wrote:

> type TMyObj = class
>  private
>MyPWord:PWord;
>...
>  end;
> 
> procedure TMyObj.Some;
> begin
>  ...
>  Inc (Cardinal (MyPWord), 2);
>  ...
> end;
> 
> and compiler says %subj%
> 
> This code works fine on 32bit compiler, but what should I change to get
> this running on 64bit and get the code still compatible with 32bit
> compiler as well.

Change
 Inc (Cardinal (MyPWord), 2);
into
 Inc (MyPWord);

(note: *without* the "2"; that is implicit because MyPWord points to data items 
of size 2)


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[fpc-pascal] Error: Can't take the address of constant expressions

2011-02-21 Thread Roland Turcan 
Hello all,

I have this code:

type TMyObj = class
  private
MyPWord:PWord;
...
  end;

procedure TMyObj.Some;
begin
  ...
  Inc (Cardinal (MyPWord), 2);
  ...
end;

and compiler says %subj%

This code works fine on 32bit compiler, but what should I change to get
this running on 64bit and get the code still compatible with 32bit
compiler as well.

Thanks.

-- 
Best regards, TRoland
http://www.rotursoft.sk
http://exekutor.rotursoft.sk

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