On Jan 29, 2013, at 5:02 PM, Orion Poplawski wrote:
> On 01/29/2013 03:21 AM, Jerry wrote:
>>
>> Hi Orion,
>>
>> This is puzzling. I can't see what could possibly be causing this. (By
>> "this" I mean the x02.adb example, as I haven't looked any of the others.) I
>> have not set ranges for any of the entities involved. (In Ada, you can
>> specify an allowed range for a variable. For instance, one could specify
>> that r1 is constrained between 0.0 and 1.0 and any attempt to assign a value
>> outside that range would raise an overflow (I think) exception.) So I don't
>> see where there is an opportunity to overflow either r1, a 64-bit float or
>> r( ), a 32-bit integer.
>>
>> FWIW, GNAT does something a little controversial--it defaults to disabling
>> overflow checking. The controversy is that this compiler is then, by
>> default, not an Ada compiler. But I don't see how that is apropos to this
>> situation.
>>
>> Can you try running this program and report the results?
>>
>>
>> with Ada.Text_IO; use Ada.Text_IO;
>> procedure Test_Overflow is
>> r : Integer;
>> r1 : Long_Float := 0.3;
>> begin
>> Put_Line("Running....");
>> r := Integer((r1 * 255.001) - 0.499999999999999);
>> end Test_Overflow;
>>
>>
>> Compile and run:
>>
>> $ gnatmake Test_Overflow.adb
>> $./test_overflow
>>
>> I also tried it with overflow checking turned on:
>>
>> $ gnatmake -gnato Test_Overflow.adb
>> $./test_overflow
>>
>> It works either way on my system.
>
>
> [orion@vmrawhide ~]$ gnatmake Test_Overflow.adb
> gcc -c Test_Overflow.adb
> Test_Overflow.adb:2:11: warning: file name does not match unit name, should
> be "test_overflow.adb"
> gnatbind -x Test_Overflow.ali
> gnatlink Test_Overflow.ali
>
> [orion@vmrawhide ~]$ ./Test_Overflow
> Running....
>
> raised CONSTRAINT_ERROR : Test_Overflow.adb:7 overflow check failed
> [[orion@vmrawhide ~]$ rm Test_Overflow Test_Overflow.o Test_Overflow.ali
> [orion@vmrawhide ~]$ gnatmake -gnato Test_Overflow.adb
> gcc -c -gnato Test_Overflow.adb
> Test_Overflow.adb:2:11: warning: file name does not match unit name, should
> be "test_overflow.adb"
> gnatbind -x Test_Overflow.ali
> gnatlink Test_Overflow.ali
> [orion@vmrawhide ~]$ ./Test_Overflow
> Running....
>
> raised CONSTRAINT_ERROR : Test_Overflow.adb:7 overflow check failed
>
>
> --
> Orion Poplawski
> Technical Manager 303-415-9701 x222
> NWRA, Boulder Office FAX: 303-415-9702
> 3380 Mitchell Lane or...@nwra.com
> Boulder, CO 80301 http://www.nwra.com
Orion:
I've queried the oracle (comp.lang.ada).
Jerry
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