Character array constructor with len=* bug?

I am running version: ifort (IFORT) 12.1.5 20120612

My problem is basically that when characters are passed to a subroutine with len=*, the array constructor does not automatically take the maximum length as specified, but instead uses the length of the last argument to specify the type. This leads to truncated strings in some cases. If the lengths of a and b in the code snippet below are explicitly specified in the declaration, the constructor works correctly. If the constructor is explicitly typed, the constructor also works correctly.

Example Code:

module tst_char
 contains
    subroutine write_char(a, b)
    character(len=8), dimension(2) :: chars
    character(len=*), intent(in) :: a
    character(len=*), intent(in) :: b

    chars = (/ a , b /)
    write(*,*) 'array first element; auto constructor: ', chars
    chars = (/ character(len=20) :: a , b /)
    write(*,*) 'array first element; specified constructor: ', chars
    write(*,*) '-----'
    end subroutine write_char
end module tst_char

program run_char
    use tst_char
    call write_char('short', 'longer')
    call write_char('longer', 'short')
    call write_char('longer', 's')
end program run_char

Output:

 array first element; auto constructor: short   longer  

 array first element; specified constructor: short   longer  

 -----

 array first element; auto constructor: longe   short   

 array first element; specified constructor: longer  short   

 -----

 array first element; auto constructor: l       s       

 array first element; specified constructor: longer  s       

 -----

The snippet is also attached for convenience.

Patrick