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

Sven Barth pascaldragon at googlemail.com
Fri Oct 12 21:51:13 CEST 2018

On 10/12/18 7:21 PM, Dmitry Boyarintsev wrote:
> On Fri, Oct 12, 2018 at 1:07 PM Sven Barth via fpc-devel
> <fpc-devel at lists.freepascal.org <mailto:fpc-devel at lists.freepascal.org>>
> wrote:
>     Dmitry Boyarintsev <skalogryz.lists at gmail.com
>     <mailto:skalogryz.lists at gmail.com>> schrieb am Fr., 12. Okt. 2018,
>     17:26:
>         Maybe "Boolean8"  type should help instead? 
>         David, could you please test with Boolean8 instead of ByteBool?
>     Boolean8 is an alias to Boolean. But if you need to work with 1 and
>     0, but have 4 Byte width then you could try Boolean32. 
> Hmm, this is odd.
> https://www.freepascal.org/docs-html/ref/refsu4.html
> Boolean8, size=1, ord=1 
> "In addition to the simple Boolean type, the additional Boolean8,
> Boolean16, Boolean32 and Boolean64 types exist. There are in fact
> integer types, which are assignment-compatible with the simple boolean
> type. As an integer, the values for True and False are 1 and 0. This can
> be used to interfac with C code that defines a boolean of this size with
> values 0 and 1."
> Boolean8 is not exactly an alias to Boolean, as it's expected to act as
> an integer, rather than _Bool. (and would be expected? to be passed an
> integer).
> However, fpc 3.0.4 doesn't have Boolean8 as builtin type. Instead it
> provides Boolean16+ only.  Maybe it's available in trunk only.

All the Pascal Boolean types are not "Integer types". You can't assign
any of them to a Integer or whatever without typecasting. They *all*
behave like Boolean, because that was the way they were added. They are
all 1-bit zero extended to the specified size. Look at the compiler
sources, they are all implemented as pasboolSIZE, including Boolean. The
documentation simply is *wrong* here.
Compare this to the *Bool family of types that are 1-bit *sign*-extended
to the specified size.

Now for the problem at hand the question is either if the ABI is
implemented incorrectly or that a new kind of Boolean type is required
to correctly represent the _Bool type needed by Objective C.


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