[Bug ada/21937] Member record alignment triggering an ICE

[macro at linux-mips dot org]

------- Additional Comments From macro at linux-mips dot org  2005-06-07 12:14 -------
> That's not quite true, the type is not the same.

 It's hard to argue for me as Ada is not a language I'm familiar with, but
the problematic assignment is:

return Ch.Attr;

in Get_Character_Attribute() and both Ch.Attr and the return value of the
function are declared as Character_Attribute_Set, so I guess they are both
of the same type, aren't they.

> How does that change the ABI for the containing record type?  The type is laid
> out only once.  As for members, this is only done for non-aliased members so ABI
> considerations are irrelevant.

 Of course it changes the ABI -- if any member of a record (which is an
equivalent to a C structure) gets its alignment increased, then the alignment
of the containing record (structure) gets adjusted appropriately.  Otherwise
the member's record alignment requirement couldn't possibly be satisfied at
the link time.  And of course the alignment does matter for platforms that
care about alignment as different machine code may be needed to access data.

> > 2005-06-07  Maciej W. Rozycki  <macro@linux-mips.org>
> > 
> >         * ada/decl.c (make_packable_type): Use the same alignment for the new
> >         type.
> 
> That would defeat the purpose of make_packable_type.

 If I understand code correctly compute_record_mode() should still be able to
use one of the integer modes for platforms that don't care about alignment.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21937