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Date: Thu, 23 May 2013 09:09:25 -0700 (PDT)
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Subject: Re: Simple loop with a strange output
From: Luca Cappelletti <luca.cappelletti@gmail.com>
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Xref: number.nntp.dca.giganews.com comp.lang.ada:181733
Date: 2013-05-23T09:09:25-07:00
List-Id: <comp.lang.ada>

Il giorno gioved=EC 23 maggio 2013 16:41:24 UTC+2, Adam Beneschan ha scritt=
o:
> On Thursday, May 23, 2013 7:37:24 AM UTC-7, Adam Beneschan wrote:
>=20
> > On Thursday, May 23, 2013 6:53:19 AM UTC-7, Luca Cappelletti wrote:
>=20
> =20
>=20
> > > do you know what's happening?
>=20
> =20
>=20
> > Overflow.
>=20
> >=20
>=20
> > The largest possible value of an "integer" type on this platform is (2*=
*31)-1.  So when X hits 2**30 and then you double it, the actual value, 2**=
31, won't fit in an integer.  If you use the right flags when compiling (I =
don't remember what they are),=20
>=20
>=20
>=20
> OK, if you compile with -gnato, it will do the check, and now the program=
 will die on a Constraint_Error instead of getting into an infinite loop.
>=20

Yes this is the new output:

$ gnatmake -gnato hello.adb=20
gcc-4.4 -c -gnato hello.adb
gnatbind -x hello.ali
gnatlink hello.ali
$ ./hello
Start counting

          1
          2
          4
          8
         16
         32
         64
        128
        256
        512
       1024
       2048
       4096
       8192
      16384
      32768
      65536
     131072
     262144
     524288
    1048576
    2097152
    4194304
    8388608
   16777216
   33554432
   67108864
  134217728
  268435456
  536870912
 1073741824

raised CONSTRAINT_ERROR : hello.adb:9 overflow check failed

do you know why the overflow checking is off by default?
I mean I expect gnat force me to understand my errors via it's own debug me=
ssages instead works closed how gcc do for C leaving developer into the dar=
k

thank you very much

Luca