Re: A smaller self contained test case. Was: Compiler Bug or what I'm doing wrong?

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

On 24 Jun 2006 14:27:16 +0200, M E Leypold wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
> 
>> ARM 13.13.2 (9) reads:
>> 
>>    "If T is a discriminated type, discriminants are included only if they
>> have defaults."
> 
> I understood it like this: If the discrimant has defaults the type is
> definite (translate that as "has fixed memory allocation
> requirements"). Then 'Read is expected to handle the type. Else (no
> default discriminant) the type is indefinite ("no fixed memory
> allocation requirement") and 'Input would be the appropriate function
> to read from a Stream, but it would essentially read the discriminats,
> allocate memory and then invoke 'Read. 

Input is always appropriate, Read only if constraints are fixed during
object life time [informally].

BTW, I wouldn't use discriminants with defaults, and in any case, would use
Input for them. Further, in this particular case, I'd expect Read be less
effective than Input:

1. You have the discriminant stored anyway (that was the choice about
having the defaults), so you cannot use one stored value of the
discriminant for all 400 fields, even if they had it same.

2. Read means that you have one extra initialize / finalize pair. Input
does not:

declare
   X : Foo renames Foo'Input (S); -- Initializes only once
begin

[...]
> The hypothesis that the wrong finalizers are being run could be tested
> of course (by using a custom controlled type), but I haven't done it
> yet (fixing my application or getting a new Gnat as obviously
> priority).

My experience with GNAT tells me: slowly, don't hurry. You never know which
new bug it could have. (:-()

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