pragma Convention ignored (sometimes)

[Anonymous Coward <bogus_addy@bogus_domain.net>]

In article <wccbr11gx1l.fsf@shell01.TheWorld.com>, Robert A Duff wrote:
> Colin Paul Gloster <Colin_Paul_Gloster@ACM.org> writes:
> 
>> A compiler is not obliged to implement a pragma.
> 
> Compilers are obliged to implement the language defined pragmas as
> specified in the RM.   What this means in practise depends on the
> pragma.  

What about Pragma Convention?

I've noticed that gnat will sometimes honor a pragma convention on an
enumerated type (which means extending the size to 32 bits on an x86
platform), but in other cases it seems to ignore the pragma
convention.  ie, the following code:

  type Some_Enum_Type is (one, two, three);

  pragma Convention (Convention => C, Entity => Some_Enum_Type);

should create a 32 bit enum, but in fact doing a 'size reveals that
it's 2 bits!