Semantics of MODIFY_EXPR with CONSTRUCTOR rhs

[Laurent GUERBY]

Source from the ACATS testcase:
     TEST ( "C52010A" ,  "CHECK THAT RECORD ASSIGNMENTS USE ""COPY""" &
                         " SEMANTICS" );

     DECLARE
          TYPE  REC  IS
               RECORD
                    X , Y  :  INTEGER ;
               END RECORD;
          R  :  REC ;
     BEGIN

          R  :=  ( 5 , 8 ) ;
          R  :=  ( X => 1 , Y => R.X ) ;
          IF  R  /=  ( 1 , 5 )  THEN
               FAILED ( "WRONG VALUE  (1)" );
          END IF;

There's nothing "undefined" in Ada in the second assignment, and that's
what the test is checking.

Laurent

On Mon, 2004-08-02 at 10:15, Gabriel Dos Reis wrote:
> | On Sun, Aug 01, 2004 at 11:20:06PM -0400, Richard Kenner wrote:
> | > Suppose we have this in .t03.original:
> | > 
> | >   r = {.x=5, .y=8};
> | >   r = {.x=1, .y=r.x};
> | > 
> | > Is the second statement valid?
> 
> The second statement is valid.  The syntactic and grammatical validity
> is no valid different from the situation 
> 
>    struct S {
>       void* data;
>    };
> 
>    strust S s = { &s.data };
> 
> | ...
> | > What's supposed to be happening here?
> 
> My understanding is that it is a behvaiour unspecified by the C99
> standard, 6.7.8 Initialization:
> 
>        [#23] The order in which any side effects  occur  among  the
>        initialization list expressions is unspecified.130)
> 
> Footnote 130 says:
> 
>        130In  particular, the evaluation order need not be the same
>           as the order of subobject initialization.
> 
> 
> I would suggest we warn user, and let optimizer decides ;-)
> 
> -- Gaby
> 
>