(j3.2006) Fwd: BOZ incompatiability in Fortran standards

[Dan Nagle]

Hi,

With Steve's permission, this may be of interest.

> Begin forwarded message:
> 
> From: "Steven G. Kargl" <kargl at troutmask.apl.washington.edu>
> Subject: BOZ incompatiability in Fortran standards
> Date: October 4, 2017 at 13:26:12 MDT
> To: danlnagle at me.com
> Reply-To: kargl at uw.edu
> 
> Hi Dan,
> 
> I know/suspect that you are busy with finalizing F2015.  I just
> noticed a major incompatibility for BOZ in a data-statement between
> F95 and F03 and the later standards F08 and F15.  Neither F08
> nor F15 acknowledge this problem.  Here are the excerpts:
> 
> F95, p. 63
> 
>  If a data-statement-constant is a boz-literal-constant, the corresponding
>  object shall be of type integer.  A data-stmt-constant that is a
>  boz-literal-constant is treated as if the constant were an int-literal-
>  constant with a kind-param that specifies the representation method with
>  the largest decimal exponent range supported by the processor.
> 
> F2003, p. 89
> 
>  If a data-stmt-constant is a boz-literal-constant, the corresponding
>  variable shall be of type integer.  The boz-literal-constant is treated
>  as if it were an int-literal-constant with a kind-param that specifies
>  the representation method with the largest decimal exponent range
>  supported by the processor.
> 
> F2008, p. 106
> 
>  If a data-stmt-constant is a boz-literal-constant, the corresponding
>  variable shall be of type integer.  The boz-literal-constant is treated
>  as if it were converted by the intrinsic function INT (13.7.81) to type
>  integer with the kind type parameter of the variable.
> 
> F2015, p. 117
> 
>  If a data-stmt-constant is a boz-literal-constant, the corresponding
>  variable shall be of type integer.  The boz-literal-constant is treated
>  as if it were converted by the intrinsic function INT (16.9.100) to type
>  integer with the kind type parameter of the variable.
> 
> For this discussion, assume the kind type parameters for two integer
> types are enumerated with 4 and 8.  Further, assume that INTEGER(8)
> has a larger decimal exponent range than INTEGER(4).  Then, the above
> statements, changes how a Fortran processor interprets 
> 
>   INTEGER(4) I          ! Yes, the 4 is nonstandard, but used for discussion.
>   DATA I/Z'FFFFFFFFF'/  ! F95/F03 treat BOZ as INTEGER(8),
>   PRINT *, I
>   END
> 
> In F95 and F03, Z'FF' is converted/treated as an INTEGER(8).  In F08
> and F15, Z'FF' is converted directly to INTEGER(4). 
> 
> For gfortran the current behavior gives
> 
> troutmask:sgk[248] gfortran6 -static -o z b.f90 -Wall && ./z
> b.f90:2:23:
> 
>    data i /z'fffffffff'/
>                       1
> Error: Arithmetic overflow converting INTEGER(16) to INTEGER(4) at (1).
> This check can be disabled with the option '-fno-range-check'
> 
> -- 
> Steve
> http://troutmask.apl.washington.edu/~kargl/


--

Cheers!
Dan Nagle




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