mixed.doc

汇编&c语言code

		Converting Mixed-Language Source Files

This directory contains	mixed-language example programs	and macros.

The following source files are the sample programs from	Chapter	6,
"Assembly-to-High-Level Interface," of the Mixed-Language Programming
Guide:

   BA.ASM	    Assembly module to be called from BASIC
   CA.ASM	    Assembly module to be called from C
   FA.ASM	    Assembly module to be called from FORTRAN
   PA.ASM	    Assembly module to be called from Pascal
   BAMAIN.BAS	    BASIC main program that calls assembly module
   CAMAIN.C	    C main program that	calls assembly module
   FAMAIN.FOR	    FORTRAN main program that calls assembly module
   PAMAIN.PAS	    Pascal main	program	that calls assembly module

In addition, the following files are provided:

   POWER2.ASM	    Macro version of assembly module that can be called
		    from BASIC,	C, FORTRAN, or Pascal.
   MIXED.INC	    Mixed language macros.
   MIXED.DOC	    This file.

The version of MIXED.INC provided with MASM 5.1	is smaller than	the
MASM 5.0 version because most of the functionality has now been	built
into MASM and the macros are no	longer needed. The following macros
are still supported in MIXED.INC:

       Macro	      Purpose

       ifFP	      Assembles	statement if the memory	model uses far data

       FP	      Provides ES override if the memory model uses far	data

       pLes	      Loads data (through ES for far data)

       pLds	      Loads data (through DS for far data)

To use these macros with MASM 5.1, you should include MIXED.INC	after
using .MODEL. The macro	syntax is shown	below:

ifFP  statement

  Assembles the	statement if the memory	model uses far data. This
  macro	can be used to push segment registers or take other
  action that is only required for far data. For example,

      ifFP     push  ds

  pushes the DS	register in compact, large, and	huge memory
  models, but has no effect in small and medium	models.

FPoperand

  Gives	an ES override if the memory model uses	far data. In
  models that use near data, FP	is null. For example,

      mov      ax,FP[bx]

  assembles as

      mov      ax,es:[bx]

  in compact, large, and huge memory models, but as

      mov      ax,[bx]

  in small and medium models.

pLes  register,address
pLds  register,address

  Loads	a pointer from the specified address to	the specified
  register. If the memory model	uses far data, the segment
  portion of the address will be moved into ES or DS, depending
  on the macro used. For example,

      pLes    bx,arg1

  is assembled as

      les     bx,arg1

  in compact, large, and huge memory models, but as

      mov     bx,arg1

  in small and medium models.

The other macros in the	MASM 5.0 version of MIXED.INC are provided for
compatibility with MASM	5.0, but are not documented. The rest of this
file discusses compatibility options for source	code that uses 5.0
high-level-language macros. If you did not own MASM 5.0, you should
ignore the rest	of this	file. Do not use the other macros in
MIXED.INC.

You can	use the	following macros if you	have source code that uses the
macros provided	with MASM 5.0.

       Macro	      Purpose

       setModel	      Sets memory model	passed from a DOS command line.
		      No longer	needed because the expression operator
		      now enables you to evaluate text macros passed
		      from the command line directly.

       hProc	      Initializes a procedure. Replaced	by new
		      attributes of the	PROC directive when you
		      specify a	language argument to the .MODEL
		      directive.

       hLocal	      Initializes local	variables. Replaced by new
		      functionality of the LOCAL directive.

       hRet	      Returns from a procedure.	Replaced by new
		      functionality of the RET instruction.

       hEndp	      Terminates a procedure. Replaced by new
		      functionality of the ENDP	directive.

The 5.1	versions of these macros are different than the	MASM 5.0
versions. The new macros use new MASM features to simulate the same
functionality more efficiently.	Do not use the MIXED.INC provided with
MASM 5.0. It will not work under MASM 5.1.

Rather than use	the old	macros,	you may	want to	convert	your source
files to use the built-in mixed	language features of MASM 5.1. The
conversion is straightforward and can be done easily with a text
editor.

The following changes can be made to source files that use macros from
the 5.0	MIXED.INC. The source file POWER2.ASM on the MASM 5.1
distribution disk is an	example	of a converted source file. You	can
compare	it with	the POWER2.ASM supplied	with MASM 5.0.

  o You	must define a a	memory model argument and a language argument
    to the .MODEL directive to use the new mixed-language features of
    MASM 5.1. You can do this within the source	file:

      .MODEL small, c

    Alternately, you can pass the arguments in from the	command	line
    using /D. In MASM 5.0, you had to use the setModel macro to
    receive a model argument passed on the command line. You only
    needed to define the language symbol "cLang" for C;	no
    definition was needed for other languages.

    The	5.0 source line	to accept the argument would be:

       setModel

    For	MASM 5.1, change to:

       %      .MODEL model,lang

    Notice that	the expression operator	(%) is required	so that	MASM
    can	evaluate text arguments	passed from the	command	line.

    The	5.0 command line to define C small model would be:

       MASM /MX	/Dmodel=small /DcLang power2;

    For	MASM 5.1, change this to:

       MASM /MX	/Dmodel=small /Dlang=C power2;

  o Replace references to the hProc macro with the PROC	directive.
    Remember, new features of the PROC directive only work when	a
    language argument is given for the .MODEL directive. The 5.0
    macro syntax was:

       hProc  <name [NEAR|FAR]> [,<USES reglist>] [,arglist]

    The	5.1 syntax is:

       name PROC [NEAR|FAR] [,USES reglist] [,arglist]

    The	syntax for each	MASM 5.0 argument in the arglist was

       argument[:[NEAR|FAR] type]

    where the type could be BYTE, WORD,	DWORD, FWORD, QWORD, TBYTE, or
    PTR	(to indicate that the variable is a pointer).

    The	syntax for each	MASM 5.1 argument is:

       argument[:[[NEAR|FAR] PTR] type]

    where the type can be BYTE,	WORD, DWORD, FWORD, QWORD, TBYTE, or a
    structure type. Note that structure	types can now be given.	Also,
    PTR	is part	of the syntax rather than a type. If PTR is given with
    a type, then it means that the variable is a pointer to a variable
    of the given type. This information	makes no difference in what
    MASM assembles, but	it can be used by the CodeView debugger.

    For	example, consider the following	MASM 5.0 source	line:

       hProc   <doTask FAR>, <USES si di>, count:BYTE, array:PTR, number

    It should be changed to the	following for MASM 5.1:

       doTask  PROC FAR	USES si	di, count:BYTE,	array:PTR WORD,	number

    Notice that the array is now declared as pointer to a word (or an
    array of words). In the 5.0 syntax it was simply a pointer to an
    object of undefined size.

  o Replace references to the hLocal macro with	the LOCAL directive.
    The	syntax for the 5.0 hLocal macro	was:

       hLocal  varlist

    The	MASM 5.1 syntax	is:

       LOCAL   varlist

    The	syntax for each	5.0 variable was:

       variable[:[NEAR|FAR] type]

    The	syntax for each	5.1 variable is:

       variable[[count]][:[[NEAR|FAR] PTR] type]

    The	difference is the same as the difference for arguments to the
    PROC directive. In addition, you can allocate local	arrays by
    specifying a count (in brackets) following the variable name. For
    example:

       LOCAL   work[20]:WORD, string:PTR BYTE

    This allocates a local array of 20 words called "work" and a
    pointer to byte (called "string").

  o Replace references to the hRet macro with the RET instruction.

  o Replace references to the hEndp macro with the ENDP	directive
    preceded by	the procedure name. For	example, change

       hEndp

    to
       procname	ENDP

  o Under MASM 5.1, labels within a procedure are local	to the
    procedure if the language argument is given	for the	.MODEL
    directive. For example, if you use the label "exit:" in one
    procedure, you can use it again in another procedure. A label
    inside a procedure can be made global to the source file by
    putting two colons after it (example, "glabel::"). Under MASM
    5.0 all labels were global to the source file.

  o Note that the 5.0 macros did not automatically handle 80386
    features such as 32-bit pointers. The 5.1 features do. For
    example, if	you use	the .386 directive before the .MODEL directive
    to enable 32-bit segments, near pointers declared with PTR will be
    32 bits wide and far pointers will be 48 bits wide.