a.f90

program exceptions
implicit none
integer :: s, stat

try
    ! Possible failure will be caught in the `catch default` block
    call mysum(5, s)
catch default
    error stop
end try
print *, s    

! The `fallible` subroutine cannot be called outside an error handling context, so this will give a compiler error
! if uncommented:
!call mysum(5, s)

contains

    fallible subroutine mysum(n, s)
    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

    fallible subroutine myallocate(n, A)
    integer, intent(in) :: n
    integer, allocatable, intent(out) :: A(:)
    allocate(A(n), failing=.true.)
    end subroutine

end