https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126799
Bug ID: 126799
Summary: Misuse of span as element size in shmem collective
subroutines implementation
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: mikael at gcc dot gnu.org
Target Milestone: ---
In collsub_reduce_array, the span is used to initialize the array element size:
elem_size = GFC_DESCRIPTOR_SPAN (desc);
which is then used to dispatch to specific evaluation and assignment functions.
This is wrong, the span is the memory address difference between two
consecutive elements, the element size itself may well be smaller than that.
Testcase, fails with the shared memory coarray implementation:
program prog
implicit none
integer, parameter :: k = 2, n = 5
type t
integer(kind=k) :: c1, c2
end type
type(t), target :: x(n)
integer(kind=k), pointer :: p(:)
integer :: i, icount
icount = num_images()
x = [ (t(i*this_image(),i+this_image()), i=1,n) ]
p => x%c1
call summation(p)
print *, icount
print *, x%c1
if (any(x%c1 /= [ ((icount * (icount + 1) / 2) * i, i=1,n) ])) error stop 1
contains
subroutine summation(a)
integer(kind=k), pointer, intent(in) :: a(:)
call co_sum(a)
end subroutine
end program
Output:
8
8
8
8
8
8
8
36 0 108 0 180
36 0 108 0 180
36 0 108 0 180
36 0 108 0 180
36 0 108 0 180
36 0 108 0 180
36 0 108 0 180
ERROR STOP 1
ERROR STOP 1
ERROR STOP 1
ERROR STOP 1
ERROR STOP 1
ERROR STOP 1
ERROR STOP 1
8
36 0 108 0 180
ERROR STOP 1
Expected output:
8
8
8
8
36 72 108 144 180
36 72 108 144 180
36 72 108 144 180
36 72 108 144 180
8
8
8
8
36 72 108 144 180
36 72 108 144 180
36 72 108 144 180
36 72 108 144 180
