Re: 'Size hack for enumerated types

[Victor Porton <porton@narod.ru>]

AdaMagica wrote:

> On Monday, July 7, 2014 10:23:06 PM UTC+2, Victor Porton wrote:
>> Simon Wright wrote:
>> > Victor Porton <porton@narod.ru> writes:
>> >> Where in the Reference Manual it is said that Ada enumeration types
>> >> are "equivalent" to C int (=enum) type?
>> > Annex B.1 (http://www.ada-auth.org/standards/12rm/html/RM-B-1.html),
>> > 2  The Convention aspect is used to indicate that an Ada entity should
>> >    use the conventions of another language.
>> > 21 If the Convention aspect is specified for a type, then the type
>> > shall
>> >    either be compatible with or eligible for the specified convention.
>> No reason to assume either of:
>> 1. Ada enumeration is compatible with C int/enum.
>> 2. Ada enumeration is eligible for the specified convention (the
>> convention C).
>> This is a work for a future standard.
>> It seems that the current one does not assert neither 1 neither 2. :-(
> 
> B.1(21/3) says "shall", so RM 1.1.5(3) applies. The compiler must reject
> the code if the enumeration is not compatible with C.

It could be able to meaningfully reject the code, only it knew the C 
function profile. But what it known about the C function profile is only 
what is provided in our pragma. Certainly the C function profile which we 
provide is compatible with itself :-)

So, the C code is compatible with some Ada function profile, but not 
necessarily with one we provide.

Just logic.

> B.1(2/3) only says "should". So what does this mean? I gather together
> with (21), we're safe to assume it works.

-- 
Victor Porton - http://portonvictor.org