[cffi-devel] CFFI and FORTRAN CHARACTER*(*)

[Martin Simmons]

>>>>> On Mon, 7 Jun 2010 11:12:47 -0600, Mark Hoemmen said:
> 
> On Mon, Jun 7, 2010 at 10:56, Martin Simmons <martin at lispworks.com> wrote:
> >>>>>> On Sat, 5 Jun 2010 16:12:58 +0200, Juan Jose Garcia-Ripoll said:
> >>
> >> CHARACTERs in Fortran are just pointers of type char*, just like in C, and
> >> just like any other fortran array. There is no terminating null and the
> >> fortran functions get the length either from some argument or because they
> >> assume a given size (for instance in Lapack it is a one-character string
> >> what the function expects)
> >
> > Are you sure about?  I think the lengths are passed as implicit arguments at
> > the end of the argumwnt list.
> 
> Not on any Fortran compilers I've seen, at least when dealing with
> LAPACK.  Replacing CHARACTER*(*) with "char* const" when calling
> LAPACK routines that take CHARACTER*(*) arguments works perfectly fine
> with all the Fortran compilers I've encountered (e.g., gfortran, Intel
> Fortran compiler, IBM's xlf).

Maybe LAPACK is compiled with options that make this work (or nothing looks at
the length arguments), but when I compile the code below with gfortran it
clearly passes the string lengths 4 and 3 as extra arguments.

      INTEGER FUNCTION ILAENV( NAME , NN )
      CHARACTER*( * )    NAME, NN
      ILAENV = ICHAR( NAME( 1: 1 ) )
      RETURN
      END

      INTEGER FUNCTION ZZZ( )
      ZZZ = ILAENV("fooo", "bar")
      RETURN
      END


	movl	$3, %ecx
	movl	$4, %edx
	movl	$.LC0, %esi
	movl	$.LC1, %edi
	call	ilaenv_


-- 
Martin Simmons
LispWorks Ltd
http://www.lispworks.com/