Re: [RFA/sparc64] internal-error printing return value (Ada array)

Joel Brobecker
2006-11-12T00:22:15Z

> > 2006-11-10 Joel Brobecker <brobecker@adacore.com>
> >
> > * sparc64-tdep.c (sparc64_structure_or_union_p): Accept array
> > types if the type length is 32 bytes or less.
> >
> > Fixes the two FAILs above, no regression.
> > OK to apply?
>
> I don't think this is the right fix; the length check almost cetainly is.
>
> To decide what is the right fix, we need to investigate this a bit further.
> I suspect that Ada arrays arereally treated as structures where all members
> have the same type.

In Ada, arrays can take many forms, and as a result, you have
3 types of arrays:

. statically known arrays (where the array bounds are known at
compile time), are implemented using a memory buffer. This is
our case here.

. Then we have fat pointers: This is a structure that contains
two pointers, one to a structure containing the array bounds,
and one pointer to the memory buffer itself. We use that for
arrays whose bounds are not known at compile time.

. Lastly, we have thin pointers: This is a pointer to the second
field of a structure that resembles the fat pointer.

> So the first question I have is whether these indeed
> have "fields".

Is this question still relevant after the description above?
I am not sure I understand it.

> You should also check how small arrays are passed as arguments to a
> function.

This is described by the Ada Reference Manual: Arrays are always
passed by reference. So a function taking a parameter of our static
array type will have the array passed by reference. As a result,
the the array parameter will be a REF to a TYPE_CODE_ARRAY.

> Here the magic length will be 16 bytes instead of 32 bytes.

I don't understand this part. Why 16 bytes instead of 32?
If the total size of the array is 32 bytes, shouldn't the compiler
return it through %o0 - %o7?

--
Joel