From rz48@rz.uni-karlsruhe.de Wed Oct 2 10:52:27 1996 Received: from nz11.rz.uni-karlsruhe.de (nz11.rz.uni-karlsruhe.de [129.13.64.7]) by dkuug.dk (8.6.12/8.6.12) with ESMTP id KAA28663 for ; Wed, 2 Oct 1996 10:51:36 +0100 Message-Id: <199610020951.KAA28663@dkuug.dk> Received: from ry73.rz.uni-karlsruhe.de by nz11.rz.uni-karlsruhe.de with SMTP (PP); Wed, 2 Oct 1996 11:47:29 +0200 Received: by ry73.rz.uni-karlsruhe.de (1.37.109.16/16.2) id AA126119645; Wed, 2 Oct 1996 11:47:25 +0200 Subject: N1229 (96-153) To: SC22WG5@dkuug.dk Date: Wed, 2 Oct 1996 11:47:24 +0200 (CES) Cc: sc22wg5-interop@ncsa.uiuc.edu From: hennecke@rz.uni-karlsruhe.de (Michael Hennecke) Reply-To: hennecke@rz.uni-karlsruhe.de (Michael Hennecke) X-Mailer: ELM [version 2.4 PL23] Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Content-Length: 7406 Hello! enclosed is WG5/N1229, also known as X3J3/96-153. Mallory - please store this on the J3 server. Miles - I'm still trying to upload this on your server... Jerry - if you have time at the next J3 meeting, it would be very helpful if X3J3 could review this document. Best regards, Michael ====================================================================== Michael Hennecke http://www.uni-karlsruhe.de/~Michael.Hennecke/ ---------------------------------------------------------------------- University of Karlsruhe RFC822: hennecke@rz.uni-karlsruhe.de Computing Center (G20.21 R210) No longer on BITNET :-( Zirkel 2 * P.O. Box 69 80 Phone: +49 721 608-4862 D-76128 Karlsruhe Fax: +49 721 32550 ====================================================================== ISO/IEC JTC1/SC22/WG5/N1229 X3J3/96-153 1996-09-30 From: Michael Hennecke To: WG5, X3J3 Subject: Support for C variable argument lists Reference: WG5/N1178 (X3J3/96-069) I would like to exchange the text concerning support which is in N1178 (96-069) with the following solution. The current text which uses OPTIONAL parameters on the Fortran side was a half-hearted approach, and will almost surely not work for general applications. Support of in its most general form seems to be necessary since some important application programming interfaces make heavy use of variable argument lists, e.g. all procedures with names XtVa* in the X Toolkit Intrinsics. The new solution does not need a of C_STDARG, which will be deleted from the spec of the BIND attribute in 3.1. (This also makes many "or BIND(C_STDARG)" clauses in the text superfluous.) Section 3.3.2 will be replaced by the following text: " 3.3.2 Support for variable argument lists C procedures may be called with a variable number of arguments of varying type. The argument list in the function prototype of such a procedure must contain one or more parameters followed by an #...#. The called procedure may access the varying number of actual arguments by facilities defined in the standard header ##. Fortran does not directly support this kind of procedure interfaces. NOTE: The Fortran concept of OPTIONAL arguments is less flexible. It requires the specification of all possible combinations of arguments at compile time, including their types. To provide a Fortran interface to an external procedure defined by means of C which contains an , an intrinsic module ISO_C_STDARG_H shall be provided. This module shall provide access to the following: * A derived type definition with C_VA_LIST. This type has the BIND(C) attribute and PRIVATE components. NOTE: The type C_VA_LIST defined in the Fortran binding is only used by the Fortran processor to build up the variable length argument list and pass it to the C procedure. It is not a translation of the C type #va-list# defined in ##. This latter type and the associated macros are only used in the definition of the callee, and are not required on the Fortran side. * A named constant C_VA_EMPTY of TYPE(C_VA_LIST). The value of this constant shall be distinct from any value that may result from an argument list construction by means of OPERATOR(//). * ASSIGNMENT(=) for s and s of TYPE(C_VA_LIST). The assignment shall perform a true copying of the derived type components, rather than using pointer assignments and reference counts. * An extension of the OPERATOR(//) to operands of TYPE(C_VA_LIST). may be of any type corresponding to a C data type, as specified in section 3.2 of this TR. The result is of TYPE(C_VA_LIST). Paranteses used to specify the order of evaluation have no effect on the value of the result. EDITOR'S NOTE: How restrictive should the TR be on the type of ? Only types? Arrays? Structures? C_VA_LIST objects??? * A function C_VA_ARG (AP, MOLD, POS) Description. Extract argument of type MOLD from position POS of a varying length argument list AP. Class. Transformational function. Arguments. AP shall be scalar and of type C_VA_LIST. It is an INTENT(IN) argument. It holds the internal representation of a varying length argument list. MOLD shall be of any type which is valid for in the above OPERATOR(//) extension. It is an INTENT(IN) argument. POS shall be scalar and of type default integer, with a value greater than zero. It is an INTENT(IN) argument. Result Characteristics. The result is of the same type and type parameters as MOLD. Result value. Case (i): If the element in position POS of the varying length argument list AP has the same type and type parameters as MOLD, the result value is that of this element. Case (ii): Otherwise, the result value is undefined. Elements with a value of C_VA_EMPTY are not taken into account when determining the position of an element in a varying length argument list AP. Example. If AP is C_VA_EMPTY // 5_c_int // 2.0_c_dbl // 7_c_long, then C_VA_ARG(AP,0.0_c_dbl,2) is of type REAL(c_dbl) and has the value 2.0_c_dbl. NOTE: The function C_VA_ARG is not a translation of the macro #va_arg# defined in ##. It accesses the Fortran processor's intermediate representation of the varying length argument list, not the C processor's representation as viewed in the callee. The that specifies a Fortran interface to a C procedure containing an shall specify the dummy arguments as in 3.3.1, and shall specify an additional dummy argument of TYPE(C_VA_LIST) in the position of the . INTENT shall not be specified for this argument. To indicate an empty argument list, C_VA_EMPTY shall be used as actual argument in a procedure reference. To pass a non-empty list of arguments, C_VA_EMPTY shall be concatenated by the OPERATOR(//) with the list of required arguments. C_VA_EMPTY shall be the leftmost operand of this concatenation, all other operands shall be specified from left to right corresponding to their respective position in a C procedure reference. The Fortran processor translates the intermediate representation stored in the C_VA_LIST argument into the representation expected by the C processor at a procedure reference. If the C procedure modifies its varying arguments, the object of type C_VA_LIST is modified, not the operands of the OPERATOR(//) from which it was constructed. The modified values in a C_VA_LIST data object can be extracted after the call by using the function C_VA_ARG. "