It depends on the context. In the patches, `a' is known to be
non-negative, so `INT_MAX - a' cannot overflow. If you ignore the
context and talk about the general case, then it can.
- xi
On Sat, Feb 23, 2013 at 12:25 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Greg Stark <stark@mit.edu> writes:
>> He's changing things to do
>
>> if (INT_MAX - a > b)
>> PG_THROW ("a+b would overflow")
>> else
>> x=a+b;
>
>> Why would a smarter compiler be licensed to conclude that it can
>> optimize away anything? "INT_MAX-a > b" is always well defined.
>
> Really? Can't "INT_MAX - a" overflow?
>
> regards, tom lane