equivalent to C/C++ "offsetof" ?

[jamie]

I used to be able to do something like this:

     UintPtr(@TSomeRecord(Nil).AmemberField);

I could of use "Integer" as the cast instead, can't remember but, it will give me the offset value of the field.

Jamie

[Fibonacci]

Code: Pascal  [Select][+][-]

1. writeln(UintPtr(@TSomeRecord(Nil^).AmemberField)); // objfpc
2. writeln(OffsetOf(TSomeRecord.AmemberField));       // unleashed  

[jamie]

Looks interesting. The unleased FPC compiler, that is.

[creaothceann]

*unleashed

[jamie]

*unleashed

As Elvis Presley would say! "Thank you, Thank you very much"

Jamie

[jamie]

Code: Pascal  [Select][+][-]

1. writeln(UintPtr(@TSomeRecord(Nil^).AmemberField)); // objfpc
2. writeln(OffsetOf(TSomeRecord.AmemberField));       // unleashed  

 I am kind of curious as about that "offsetof", its a compiler intrinsic? what I mean by that, can it evaluate values at compile time when building Enumerators and sets?

Example

Code: Pascal  [Select][+][-]

1. Const
2.   Enums:Array[0..4] of Integer = (OffsetOf(TRect.Left),offsetOf(TRect.top),offsetOf(TRrect.Right),offsetOf(TRect.Bottom), 10);
3.  
4. //Etc.
5.  

The same would hold true for defining enum types etc.

Jamie

[Fibonacci]

I am kind of curious as about that "offsetof", its a compiler intrinsic? what I mean by that, can it evaluate values at compile time when building Enumerators and sets?

Yes - it's a compiler intrinsic that const-folds to a plain integer at compile time, so it works anywhere a constant expression is allowed. It's part of the Composable Records feature - OffsetOf() and BitOffsetOf().

Code: Pascal  [Select][+][-]

1. const
2.   Enums: Array[0..4] of Integer = (OffsetOf(TRect.Left),offsetOf(TRect.top),offsetOf(TRect.Right),offsetOf(TRect.Bottom), 10);
3.  
4. begin
5.   for var i := 0 to high(Enums) do writeln('Enums[', i, '] = ', Enums[i]);

Code: Text  [Select][+][-]

1. Enums[0] = 0
2. Enums[1] = 4
3. Enums[2] = 8
4. Enums[3] = 12
5. Enums[4] = 10

Give it (Unleashed) a try - you might find you like it Install is super simple: use the installer, or fpcupdeluxe after adding 2 lines to the INI. It's recently synced with upstream FPC, with loads of features on top. And if you think this particular feature (these intrinsics) would be useful in stock FPC, go ahead and open a feature-request issue on GitLab - the code's ready, and the FPC team is free to take any part of it into stock FPC if they want.

[Thaddy]

I can confirm everybody should try it and the installation is a doddle.
I hesitate to use it for production code, though.
Features like above are strong additions as is some of the Warfeley code that are dangling merge requests in main and committed in unleashed. These could be committed in main as-is.

[Thaddy]

But unleashed has the adagium: commit now, debug later