On Fri, Jan 26, 2024 at 11:38:01PM +0100, FX Coudert wrote:
> > Interesting example.
> >
> > % gfcx -o z a.f90 && ./z
> > -128
> > % gfcx -o z -pedantic a.f90 && ./z
> > a.f90:5:20:
> >
> > 5 | data j /-128_int8/
> > | 1
> > Error: Integer too big for its kind at (1). This check can be disabled with
> > the option ‘-fno-range-check’
>
> That qualifies as a compiler bug, I think. Our documentation for -pedantic
> states: “Issue warnings for uses of extensions to Fortran.” and "Valid
> Fortran programs should compile properly with or without this option.”
>
> The same is true of the following, which is also valid Fortran since 95 :
>
> use iso_fortran_env
> implicit none
> complex, parameter :: z = (-128_int8, -128_int8)
> print *, z
> end
>
> Right now it fails to compile with -pedantic.
>
> Or are they illegal because of how the range should be be symmetric? I can’t
> quite find the language in the standard for that, actually. To me, they’re
> valid signed-int-literal-constant.
>
Symmetry comes from the definition of a model integer number
in 16.3.3 "Bit sequences as arguments to INT and REAL". If
'i' and 'j' are INTEGER(1), then this leads to something like
'j = abs(i)' being comforming except if 'i = -128'.
As far as literal constants, one has from Fortran 2023 p. 66
R707 signed-int-literal-constant is [ sign ] int-literal-constant
R708 int-literal-constant is digit-string [ _ kind-param ]
R709 kind-param is digit-string
R710 signed-digit-string is [ sign ] digit-string
R711 digit-string is digit [ digit ] ...
R712 sign is +
or -
I cannot find in the Standard any statement about the conversion
of a digit-string to an internal representation. I suspect it
depends on the path through the compiler. In assignments, the
signed-digit-string is likely handled as a unary operator and
operand.
--
Steve
