optimisation of overflowing integers

[Steve Kargl]

On Tue, Mar 18, 2014 at 07:53:04AM +0100, Tobias Burnus wrote:
> N.M. Maclaren wrote:
> > The errors occur at run-time - NAG Fortran is the only currently active
> > Fortran compiler that checks for such things (and you need -C=all).
> > So the answers are "no" and "no".
> 
> Try GCC/gfortran 4.9 (with the bug fix patch to PR60557), namely:
> 
> $ gfortran -fsanitize=undefined bar.f90
> $ ./a.out
> bar.f90:19: runtime error: signed integer overflow: 809078955 * 65539 
> cannot be represented in type 'integer(kind=4)'
>    0.290384561       623596113
> 

It appears that if one builds gcc without libsantize, one gets ICEs.


troutmask:sgk[204] gfc4x -o z -fsanitize=undefined ffo1.f90 
ffo1.f90: In function 'ribm':
ffo1.f90:14:0: internal compiler error: Segmentation fault
   subroutine ribm(rndm,ial)
 ^
no stack trace because unwind library not available

troutmask:sgk[206] gfc4x -o z -O2 -fsanitize=signed-integer-overflow ffo1.f90 
ffo1.f90: In function 'testribm':
ffo1.f90:18:0: internal compiler error: Segmentation fault
     ial=ial*65539
 ^
no stack trace because unwind library not available

-- 
Steve