[fpc-devel] OSX: Setting up parameters to objc_msgSend()

[Sven Barth]

Dmitry Boyarintsev <skalogryz.lists at gmail.com> schrieb am Sa., 13. Okt.
2018, 01:57:

> On Fri, Oct 12, 2018 at 6:48 PM Sven Barth via fpc-devel <
> fpc-devel at lists.freepascal.org> wrote:
>
>> Not quite: the Boolean16, Boolean32 and Boolean64 types were introduced
>> because the libraries provided by GTK required a 4-Byte boolean type that
>> worked like Object Pascal's Boolean.
>>
> That's interesting.
> Let me ask a couple of things here:
>
> 1) gboolean is a size of int (
> https://www.gtk.org/api/2.6/glib/glib-Basic-Types.html#gboolean)
> where FALSE is 0 and TRUE is not FALSE.
> https://www.gtk.org/api/2.6/glib/glib-Standard-Macros.html#TRUE:CAPS
> so, it's more -1, rather than 1 and it doesn't quite maps to Boolean
> and/or Boolean32. It's matches to LongBool.
>
> var
>   b : Boolean;
>   lb : LongBool;
>   b32 : Boolean32;
> begin
>   b := true;
>   lb := true;
>   b32 := true;
>   writeln(byte(b),' ',LongWord(b32),' ',LongWord(lb));
>   writeln(ord(b),' ',Ord(b32),' ',Ord(lb));
> end.
> Results in:
> 1 1 4294967295
> 1 1 -1
> (matches documentation)
>

This was the reason they were added:
https://bugs.freepascal.org/view.php?id=17400


> 2) why the were they named booleanN rather than gtkboolean or something?
> (I'm referring to the suggestion of using objcbool name. It seem to fit)
>

They're an extension of the existing Boolean type with merely a different
size, so why should they be named any differently? (in addition to what
Michael wrote)


>
>> Then maybe it's an issue about the ABI (maybe all values with a size < 4
>> need to be correctly extended due to the ABI).
>>
>
> I think Jonas clearly stated that ABI call works properly (to the word of
> the specification)
> The issues is that BOOL in objective-C is for Intel (macOS) is not _Bool
> but rather a signed char.
>
> As of today, Pascal doesn't provide Boolean type that behaves like a
> signed char in ABI terms.
> (Boolean, and Boolean8 are size of _Bool which matched the size of signed
> char, though treated are passed as "_Bool" following ABI rules)
>

Then maybe the type used to represent that BOOL should be a "type char"
alias instead of using one of the build in Boolean types.

Regards,
Sven

>
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