Re: [Plplot-devel] Recent f77 changes

[Arjen M. <arj...@de...>]

Hi Alan,

I get an error message with gfortran 4.6, but not with ifort.
The value is -2147483648, which is the largest negative number
that actually fits into a 32-bits twos-complement integer.

I think this is a bug in gfortran:

setting PL_FCI_MARK to -2147483647 and then printing PL_FCI_MARK-1
gives the original value but printing PL_FCI_MARK-2 produces a
compile error:

program boz
integer, parameter :: PL_FCI_MARK = -2147483647
integer, parameter :: PL_FCI_SERIF = z'1'
write(*,*) PL_FCI_MARK-1
write(*,*) PL_FCI_MARK-2
end program

produces:

boz.f90:8.10:

write(*,*) PL_FCI_MARK-2
           1
Error: Arithmetic overflow at (1)

I will report this. Meanwhile the solution would be to add the option 
-fno-range-check.

Regards,

Arjen



On 2011-01-27 11:11, Alan W. Irwin wrote:
> On 2011-01-27 01:20-0800 Alan W. Irwin wrote:
> 
>> Hi Arjen:
>>
>> I have the sed script almost working for f95.  The only problematic
>> statement generated is
>>
>>       integer, parameter :: PL_FCI_MARK = z'80000000'
>>
>> That z'80000000' causes an integer overflow.  The problem is that
>> z'80000000' is not a normal 4-byte integer.  Assuming twos-complement
>> integers, then the negative of that number is also z'80000000'.  That
>> is, it is a "negative" zero or zero with the sign bit set. Do you know
>> how to put that exact pattern of bits into a 4-byte integer in fortran?
>>
>> For now, I have simply dropped PL_FCI_MARK (since it is not used in
>> any of the examples), but it would be nice to include it for
>> completeness if you can figure out an equivalent of the above
>> parameter statement that will put that exact pattern into the
>> PL_FCI_MARK 4-byte integer.
>>
>> Also, could you comment on BOZ constants used in parameter statements
>> such as
>>
>> integer, parameter :: PL_FCI_SERIF = z'1'
>>
>> gfortran is happy to accept those, but I am not sure other Fortran
>> compilers are able to.  The issue is that hexadecimal constants are
>> sometimes used in plplotcapi.i (and the equivalent #defines in
>> include/plplot.h) so I have converted those to the BOZ form using the
>> sed script.  If the BOZ form is not acceptable to some Fortran
>> compilers in the above context, then I could use a python script to do
>> the conversions from hexadecimal constants to decimal constants.
>>
>> Further changes to the Fortran 95 examples are required by this sed
>> script approach since you cannot have local parameters in the examples
>> trying to override the parameter values set by the module.  So with
>> luck it should only be a matter of removing all those local parameters
>> that are set in the Fortran 95 examples, testing to make sure
>> everything works as before, then doing the commit. I plan to continue
>> with those steps after I get some sleep.
> 
> Hi Arjen:
> 
> Well, I stayed up a bit later and I finished these described Fortran
> 95 changes as of revision 11511.  So please take a look at the
> generated bindings/f95/plplot_parameters.h and let me know if there
> are any concerns about the BOZ form (actually just Z form) used to
> define the values of some of the parameters there. And the above
> question about a Fortran method of setting the negative zero bit
> pattern for PL_FCI_MARK still remains as well.
> 
> Aside from these questions and committing the sed script and
> a CMake custom target to use that script appropriately, I am
> done with Fortran 95 for a while.  Also, the only thing
> left on my Fortran 77 agenda is an equivalent sed-script
> approach there for generating bindings/f77/plplot_parameters.h.
> 
> Alan
> __________________________
> Alan W. Irwin
> 
> Astronomical research affiliation with Department of Physics and Astronomy,
> University of Victoria (astrowww.phys.uvic.ca).
> 
> Programming affiliations with the FreeEOS equation-of-state implementation
> for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
> package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
> Linux Links project (loll.sf.net); and the Linux Brochure Project
> (lbproject.sf.net).
> __________________________
> 
> Linux-powered Science
> __________________________
> 
 

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