Integer overflow bug in windows

[Marco Leise]

Am 10.11.2011, 00:07 Uhr, schrieb Alex Rønne Petersen  
<xtzgzorex at gmail.com>:

> On 09-11-2011 23:49, bearophile wrote:
>> Kagamin:
>>
>>> http://blogs.technet.com/b/srd/archive/2011/11/08/assessing-the-exploitability-of-ms11-083.aspx
>>
>> I'd like a runtime error when an integral overflows (unsigned numbers  
>> too, the C99 Standard is not a religion book for me), unless where  
>> asked otherwise.
>>
>> Bye,
>> bearophile
>
> If anything, we should do it like C#: have checked/unchecked arithmetic  
> blocks.
>
> - Alex

I know that the article was meant to start this discussion, but no checked  
arithmetic could have found this bug while debugging. And if it the check  
is kept even in release mode - which is untypical for asserts - the  
question is, if an exception or termination of the program would have been  
handled gracefully.

On the other hand I wouldn't mind checked arithmetic, especially since  
there are assembly instructions like JO. Could this also be used to  
execute a different branch when an overflow occurs? I mean: Would some  
code become faster and cleaner? I am so used to not having any checking  
that I cannot remember any such cases from the top of my head.

In any case blocks are the way to go, because the overflow flag is  
manipulated by too many instructions as to just write "if (overflow())  
{...}" after a statement. I don't know if we always want an Exception as  
in C# though, if people find it useful for general code flow.