개요

• 솔라나라에 설명된 어플리케이션에 대해 맨 페이지를 찾아 출력한다.
• MAN 페이지에 대한 설명은 윈디하나의 솔라나라: MAN 페이지을 참고하자.
• svcadm(8)을 검색하려면 섹션에서 8 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.

va_start(9f)

va_arg(9F)                     Kernel Functions                     va_arg(9F)

NAME
       va_arg, va_start, va_copy, va_end - handle variable argument list

SYNOPSIS
       #include <sys/varargs.h>

       void va_start(va_list pvar, name);


       (type) va_arg(va_list pvar, type);


       void va_copy(va_list dest, va_list src);


       void va_end(va_list pvar);

INTERFACE LEVEL
       Solaris DDI specific (Solaris DDI).

PARAMETERS
   va_start()
       pvar    Pointer to variable argument list.


       name    Identifier of rightmost parameter in the function definition.


   va_arg()
       pvar    Pointer to variable argument list.


       type    Type name of the next argument to be returned.


   va_copy()
       dest    Destination variable argument list.


       src     Source variable argument list.


   va_end()
       pvar    Pointer to variable argument list.


DESCRIPTION
       This  set of macros allows portable procedures that accept variable ar‐
       gument lists to be written. Routines that have variable argument  lists
       but  do not use the varargs macros are inherently non-portable, as dif‐
       ferent machines use different  argument-passing  conventions.  Routines
       that  accept  a variable argument list can use these macros to traverse
       the list.


       va_list is the type defined for the variable used to traverse the  list
       of arguments.


       va_start()  is  called to initialize pvar to the beginning of the vari‐
       able argument list. va_start() must be invoked before any access to the
       unnamed arguments. The parameter name is the identifier of  the  right‐
       most  parameter  in the variable parameter list in the function defini‐
       tion (the one just before the ", ..."). If this parameter  is  declared
       with  the  register  storage class or with a function or array type, or
       with a type that is not compatible with the type that results after ap‐
       plication of the default argument promotions,  the  behavior  is  unde‐
       fined.


       va_arg()  expands  to  an expression that has the type and value of the
       next argument in the call. The parameter pvar must  be  initialized  by
       va_start().  Each invocation of va_arg() modifies pvar so that the val‐
       ues of successive arguments are returned in turn. The parameter type is
       the type name of the next argument to be returned. The type  name  must
       be  specified  in such a way that the type of pointer to an object that
       has the specified type can be obtained by postfixing a *  to  type.  If
       there is no actual next argument, or if type is not compatible with the
       type  of the actual next argument (as promoted according to the default
       argument promotions), the behavior is undefined.


       The va_copy() macro saves the state represented by  the  va_listsrc  in
       the va_list  dest. The va_list passed as dest should not be initialized
       by a previous call to va_start() It then must be passed to va_end() be‐
       fore being reused as a parameter to va_start() or as the dest parameter
       of  a subsequent call to va_copy(). The behavior is undefined if any of
       these restrictions are not met.


       The va_end() macro is used to clean up. It  invalidates  pvar  for  use
       (unless va_start() is invoked again).


       Multiple  traversals,  each  bracketed  by  a  call  to  va_start() and
       va_end(), are possible.

EXAMPLES
       Example 1 Creating a Variable Length Command



       The following example uses these routines to create a  variable  length
       command.  This  might  be useful for a device that provides for a vari‐
       able-length command set. ncmdbytes is the number of bytes in  the  com‐
       mand. The new command is written to cmdp.




         static void
         xx_write_cmd(uchar_t *cmdp, int ncmdbytes, ...)
         {
                 va_list   ap;
                 int  i;

                     /*
                  * Write variable-length command to destination
                      */
                  va_start(ap, ncmdbytes);
                  for (i = 0; i < ncmdbytes; i++) {
                           *cmdp++ = va_arg(ap, uchar_t);
                      }
                  va_end(ap);
         }



SEE ALSO
       vcmn_err(9F), vsprintf(9F)

NOTES
       It  is up to the calling routine to specify in some manner how many ar‐
       guments there are, since it is not always  possible  to  determine  the
       number of arguments from the stack frame.


       Specifying a second argument of char or short to va_arg makes your code
       non-portable,  because  arguments  seen  by the called function are not
       char or short. C converts char and short arguments to int before  pass‐
       ing them to a function.

Oracle Solaris 11.4               12 Oct 2016                       va_arg(9F)