a.f90

program exceptions
use iso_fortran_env, only: Out_of_memory
implicit none
integer :: s

block enable (Out_of_memory)
    ! Possible failure will be caught in the `handle` block
    call mysum(5, s)
    print *, s
end block


! Possible failure will cause the program to stop here with a stacktrace at
! runtime, because `mysum` is not called within a `block enable` block
call mysum(5, s)
print *, s


handle Out_of_memory
    error stop

contains

    subroutine mysum(n, s) enable(Out_of_memory)
    integer, intent(in) :: n
    integer, intent(out) :: s
    integer, allocatable :: A(:)
    integer :: i
    call myallocate(n, A)
    do i = 1, n
        A(i) = i
    end do
    s = sum(A)
    end subroutine

    subroutine myallocate(n, A) enable(Out_of_memory)
    integer, intent(in) :: n
    integer, allocatable, intent(out) :: A(:)
    ! Can raise the Out_of_memory exception
    allocate(A(n), failing=.true.)
    end subroutine

end