Re: Exclusive file access

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sun, 30 Aug 2015 13:35:16 +0200, Florian Weimer wrote:

> * Dmitry A. Kazakov:
> 
>> No, I meant Wide_Wide_String.
>>
>> Ada's Wide_String is legally UCS-2. Windows is UTF-16. The only full
>> Unicode string type is Wide_Wide_String. For an Indo-European language
>> there is no difference, of course.
> 
> GNAT's Wide_String should be compatible with UTF-16.

In the sense that Wide_String is an array of 0..2**16-1 units of the
endianness compatible to UTF-16, yes. However the standard is silent about
endianness and alignment (a DSP processor might deploy 32-bit units per
unit)

Semantically no. Wide_String according to RM 3.5.2 (3/3) represents a
narrower set of Unicode than UTF-16.

> Wide_Wide_String definitely is not.

Definitely is. Both are to represent arrays of same sets of Unicode
characters. The representation of Wide_Wide_String is of course irrelevant
when used to specify an external file name, right?

>> Under Linux most applications simply ignore Ada standard and use String
>> encoded in UTF-8. I suppose that under Linux GNAT calmly passes String file
>> names as-is, i.e. as UTF-8 [*].
> 
> I think GNAT just passes around bytes, it does not care if it's UTF-8
> or a legacy encoding.

Yes, which is clearly against RM 3.5.2 (2/3) as the example illustrates.
The point is that the behavior one would imply from 3.5.2 and Ada.Text_IO
specification would be useless.

> As long as you don't use Wide_String—if you do use that, things get rather messy.

Both are messy. Character and Ada.Text_IO was designed prior to Unicode.
Later amendments were futile attempts to repair what needed no repair.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de