[fpc-devel] Allow record helper inheritance in Delphi mode

Ondrej Pokorny lazarus at kluug.net
Thu Aug 31 15:54:58 CEST 2017

On 31.08.2017 14:55, Sven Barth via fpc-devel wrote:
> > Yeah, they might enable record helper inheritance for example :P 
> (Record helper inheritance was documented to work for about 7 years 
> since Delphi 2007 until XE6 
> http://docwiki.embarcadero.com/RADStudio/XE6/en/Class_and_Record_Helpers_(Delphi) 
> <http://docwiki.embarcadero.com/RADStudio/XE6/en/Class_and_Record_Helpers_%28Delphi%29> 
> ).
> >
> Huh? I had developed the feature while testing with Delphi XE and 
> there record helpers did not support inheritance, only class helpers 
> did. So as long as you don't provide prove I'd say that this is a 
> documentation bug.

That's exactly what I say: record helpers don't support inheritance but 
the documentation (until XE6) says nothing about this restriction, on 
the contrary. Only in XE7 they added the "It [the ancestor list] can be 
specified only for class helper." line. See:


It is a matter of point of view if it was a documentation bug or a 
compiler bug. Embarcadero shared your opinion with "documentation bug". 
(My personal opinion is that they just forgot about inheritance when 
they implemented record helpers and then instead of fixing the compiler 
they fixed the docs - yeah because it's easier.)


I remember a compiler bug in class destructor order call in Delphi: 

There were several issue reports about it in Embarcadero Quality Central 
(which is now down, so I can't provide the links), all resolved as 
"won't fix". Embarcadero always claimed this was by design.

But when they introduced ARC they suddendly couldn't justify the design 
flaw because consequently class objects were not available in class 
destructors in ARC mode but they were available in non-ARC mode. So they 
decided to fix the order just like lots of people requested from the 
very beginning. IMO it was VERY embarrassing for Embarcadero.

By the way, FPC is affected by the very same bug: 
https://mantis.freepascal.org/view.php?id=29334 .


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