[Bug c/56917] -ftrapv detects a overflow wrongly.

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56917

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-11-03
                 CC|                            |mpolacek at gcc dot gnu.org
   Target Milestone|---                         |5.0
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed, this can be seen with ubsan as well.  The issue is that fold changes
-(long int) (ul - 1) - 1
into
(-long int) ul
For e.g. ul = LONG_MAX+1 that shouldn't be done, I'm afraid.