ieee_get_flag behavior varies for externally linked procedures?

Hello all, 

I have noticed a wierd behavior when using ieee_get_flag.

As an example consider the following.

Compiling the following as a whole (from a single .f90 file, without any compilation options), gives a False for the ieee_invalid flag for 0/0 [ attached file test2.f90 ]:

 
module my_subs
implicit none
contains
subroutine NaNsub(r1)
real,intent(out) :: r1
r1 = 0./0.
end subroutine NaNsub
end module my_subs
program test2
use ieee_exceptions
use my_subs
implicit none
logical :: NaN_found
real :: r1
call NaNsub(r1)
call ieee_get_flag(ieee_invalid,NaN_found)
print *, NaN_found
end program test2

However, if I put the module in a seperate file [test3.f90 + NaNsub.f90] compile it and link it to the main code the answer flag becomes true (no compilation options). So I think that something strange happens. Could you please check if you can reproduce this ? Could this behavior be related to the default optimizations used? I'm using v13.1.2 running in Ubuntu 13.01. 

Many Thanks,

Kostas