Re: 83/95 issue, bad code or compiler bug

[stt@houdini.camb.inmet.com (Tucker Taft)]

Jeff Creem (jeffrey.m.creem@lmco.com) wrote:


: type My_Record is
:   record
:     My_Field    : My_Subtype;
:     Other_Field : My_Integer_Type;
:   end record;

: for My_Record use
:   record
:     My_Field    at 0 range 0 .. 31;
:     Other_Field at 4 range 0 .. 31; 
:   end record;

: for My_Record'size use 2 * 32;



: with the old compiler the My_Subtype was still using all 32 bits so
: that if we had a record with My_Field := 1 and Other_Field := 2 and
: we looked at the bytes in memory associated with this record we would see


: 00 00 00 01
: 00 00 00 02

: But with this new compiler (happens to be ada 95) I get

: 01 00 00 00
: 00 00 00 02

: I suspect that the compiler is seeing that the 'size of My_Subtype is 8 and
: so then even though I have the record rep-spec it does not feel constrained to
: put this 8 bit value in any particular place in the 32 bits I have given it
: since the field is larger than the subtype requires. 


: Yuck.

This is a bug.  You should ask your compiler vendor whether a fix
is available.  The repclause clearly indicates that My_Field should occupy
4 bytes, and that means it should not just be using the high 8 bits of
the word.

: Thanks,
: Jeff

--
-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
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