On 29.01.2011 17:35, Paul Ishenin wrote:
29.01.2011 19:25, Sven Barth wrote:
Does someone know a good place to link this page from? Maybe something
where other language/compiler features are referenced from or can be
linked to in the future.
http://wiki.freepascal.org/delphi_language_features_which_fpc_does_not_have
http://wiki.freepascal.org/FPC_New_Features_Trunk
Ok, thanks.
* I have yet to test whether the restriction "Create must be first
statement in constructors" holds true (I've found a code sample that
suggests its not true)
"If a class helper has a constructor the first statement in that
constructor must be a call to the parameterless constructor." I think
this is a copy-paste from some delphi .net or c# help where
"parameterless constructor" has some special meaning.
Could be.
Regarding the algorithm I use to find the last available class helper
(this is implemented in
compiler/symtable.pas/search_last_objectpascal_classhelper):
Delphi uses the last class helper that is available in the current
scope for method resolution (and the "parents" of that class helper).
For this I walk the symtable stack and search for a def where
is_objectpascal_classhelper returns "true". This can potentially lead
to a bad runtime behavior if a project does not use any class helpers,
but includes many units (the compiler is a good example of that).
Do you (especially @Devs) think that this is a sufficient approach or
should this be done another way? (Note: I have not yet profiled
compiling the compiler once with that search enabled and once without)
Maybe to speedup the search we can mark the symtable with a flag that if
it contains a class helper? Other flags can come in future - like has
type definitions - to speedup type searches.
Perhaps searching for class helpers should be made dependent on a
modeswitch? E.g. "useclasshelpers"
That might lead to the potentially confusing behavior that a class
helper is not even found in its own unit though, although I think that
this would be a consequent behavior (the switch needs to be documented
good enough though ^^).
This switch could be enabled by default in mode Delphi.
objfpc also allows final methods and sealed classes so it needs class
helpers too. Better to allow them for all modes which support classes I
think.
I didn't say that ObjFPC should not be able to use class helpers. I only
wanted to mention the possibility to make the search for class helpers
optional in that mode. But your suggestion regarding a flag might make
this idea obsolete.
Don't forget about record helpers. And I also noticed that in delphi
class helpers and record helpers are synonims so you can define a class
helper for a record and a record helper for a class - I think FPC should
be more restrictive here.
At first I forgot them, but currently I think that I'll only finish
class helpers for now as record helpers might prove a bit more complex:
In normal classes most problems are taken care of because the extended
class is the real parent of the class helper class. I don't have that
inheritance in records though, so here one must approach that differently.
But I agree that FPC should be more strict regarding the separation of
class helper <-> record helper.
Regards,
Sven
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