type arange = -1..5;
...
b := max(a-1,-1);         /* keep b in range */

max(a-1,0)  => a-min(1,a);

The following program behaves differently under 32-bit and 64-bit
compilation.  In 64-bit the "max()" function returns a large integer
when a value is sent out of bounds (output not shown).  The point of the
max() is to keep a value from going out of bounds.  This problem does
not occur in 32-bit code.  To make sure that range checking was on in
both cases I set "a" out of range after the max().

Is this a feature of the cpu option? And/or is there a more robust way
of keeping within range?

Thanks for any help.


P.S.  I've already received the following response from Frank.

I'm not using a 64 bit machine myself, so I can only speculate. I
hope Waldek can say more about it.

I think the problem might be that GPC treats "arange" internally as
an unsigned type (i.e., as a subrange of "Cardinal", not "Integer")
and on the 64 bit machine performs the "a - 1" unsigned which causes
the range error. (On the 32 bit machine it can do it in LongestInt
which covers the range of "Cardinal" as well as negative values, but
on 64 bit, it currently doesn't support larger integer types. This
might explain the different behaviour.)

Of course, this is a GPC bug as, according to ISO, your program is
perfectly valid (given a suitable definition of "Max" which isn't
part of ISO).

So the bugfix might be to make subrange types signed when the range
allows (which would always be the case in valid ISO programs).

Frank

--------------------
program test(input,output);

type arange = 0..5;

var a,b : arange;

begin
   a:= 0;
   b := max(a-1,0);         /* keep b in range */
  writeln('here ',b,' now really go out of range ');
  a := b-1;                      /* take a out of range to make sure
range checking is on */
  writeln('there ',a);
end.

--------------------

Output

32-bit:
       here 0 now really go out of range
       a.out: value out of range (error #300 at 180e3)

64-bit
   a.out: value out of range (error #300 at 100009d2b)

32-bit compilation
   gpc maxtest.pas

64-bit
   gpc $g64pth $m64opt maxtest.pas

where $m64opt= "-mcpu=ultrasparc3 -m64"

---------------------
Here is the version output

hpc1014@sfnode0$ gpc -v
Reading specs from
/opt/gpc/20051104/lib/gcc/sparc-sun-solaris2.10/3.4.3/specs
Configured with: ../gcc-3.4.3/configure --prefix=/opt/gpc/20051104
--enable-languages=pascal
Thread model: posix
gpc version 20051104, based on gcc-3.4.3



-- Chris
Christopher Ferrall <http://econ.queensu.ca/%7Eferrall/>
Associate Professor of Economics
Department of Economics <http://www.econ.queensu.ca>
Queen's University <http://www.queensu.ca>
Kingston, Ontario
CANADA K7L 3N6     ferrallc AT post.queensu.ca
Mackintosh-Corry Rm A519
ph: 613-533-6658
fx: 613-533-6668