------- Comment #6 from burnus at gcc dot gnu dot org 2007-12-06 21:34 -------
> > but the committee seems the have lost track of why programs need specific
> > bit patterns and how they are used.
>
> See the TRANSFER intrinsic. I think J3 recognized the problems with
> specify a bit pattern. J3 also appears to have recognized the limitations
> on TRANSFER because they have allowed BOZ to appear in REAL, INT, DBLE, and
> COMPLX. Unfortunately, J3 didn't define what this means!
Well, if they had specified what it means, having different hard ware (e.g.
decimal numbers in silicon) would have been more complicated.
> > How about adding something like a "-fhex" enhancement
> > that does this ?
> This is a very nontrivial option to add, and it opens the
> door to (mis)feature creep of a extension.
Well, to allow BOZ in DATA statements (for non-integers) and for
real r = 'b0'z
it is relatively easy.
> What happens with
> x = y + Z'deadbeef' + 42
> Is Z'deadbeef' an integer or a real?
With my patch, it is an integer, only in
variable = boz
boz might be a real/complex bit patter. As soon as you have expressions on the
right-hand side, the boz is regarded as integer.
I find this clear than all the "boz + integer" is "integer+integer" but "boz +
1.0" is "real+real" convention some compilers have.
> call whoops(Z'deadbeef') ! Is this an integer or real???
With my patch it is an integer (no assignment and not in a DATA statement).
> I suppose that one can argue that gfortran can restrict BOZ to
> the simplest form of an initialization expression.
>
> real, parameter :: x = z'deadbeef' ! Allowed real bit pattern
> real, parameter :: y = z'deadbeef'+1. ! Not allowed, BOZ in a RHS expression
This plus BOZ in DATA statements is what my patch (to be submitted in a moment)
does. (Well, it does not reject the second version but regards it as integer
pattern.) The patch also gives some better diagnostic with -std=f95 and
-Wsurprising.
--
burnus at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |burnus at gcc dot gnu dot
|dot org |org
Status|UNCONFIRMED |ASSIGNED
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2007-12-06 21:34:52
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34345
