Re: Sorry to mention aliasing again, but is the standard IN6_ARE_ADDR_EQUAL really wrong?

[Laurent GUERBY]

On Sun, 2010-01-10 at 15:46 +0100, Eric Botcazou wrote:
> > The aliasing rules treat "char" specially because char is a bit like a
> > "poor main's void".
> 
> Not symmetrically though, only for the type of the lvalue expression used to 
> access the object (C99 6.5.7).

BTW in Ada if one uses address clause to overlay a 16 character string
and a 4 4-byte integer array (both aliased) which is then accessed what
can we expect GCC-wise? Are we safe from aliasing related optimizations?

FWIW the program below seems to work as expected.

Laurent

procedure P is
  subtype String16 is String (1 .. 16);
  S16 : aliased String16;
  for S16'alignment use Integer'Alignment;
  type Int4 is array (1 .. 4) of Integer;
  I4 : aliased Int4;
  for I4'Address use S16'Address;
  X : constant := 1 + 256 + 256*256 + 256*256*256;
begin
  S16 := (others => Character'Val (1));
  if I4 /= (X, X, X, X) then
     raise Program_Error;
  end if;
end P;