add_str Subroutine

    subroutine add_str(me,str)

    class(pyplot),    intent(inout) :: me  !! pyplot handler
    character(len=*), intent(in)    :: str !! str to be added to pyplot handler buffer

    integer :: n_old !! current `me%str` length
    integer :: n_str !! length of input `str`
    character(len=:),allocatable :: tmp !! tmp string for building the result

    ! original
    !me%str = me%str//str//new_line(' ')

    if (len(str)==0) return

    ! the above can sometimes cause a stack overflow in the
    ! intel Fortran compiler, so we replace with this:
    if (allocated(me%str)) then
        n_old = len(me%str)
        n_str = len(str)
        allocate(character(len=n_old+n_str+1) :: tmp)
        tmp(1:n_old) = me%str
        tmp(n_old+1:) = str//new_line(' ')
        call move_alloc(tmp, me%str)
    else
        allocate(me%str, source = str//new_line(' '))
    end if

    end subroutine add_str