From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/MAN/va_start.htm | 159 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 159 insertions(+) create mode 100644 reference/C/MAN/va_start.htm (limited to 'reference/C/MAN/va_start.htm') diff --git a/reference/C/MAN/va_start.htm b/reference/C/MAN/va_start.htm new file mode 100644 index 0000000..a35845f --- /dev/null +++ b/reference/C/MAN/va_start.htm @@ -0,0 +1,159 @@ +va_start + +
+
+
+
+
+
STDARG(3)           Linux Programmer's Manual           STDARG(3)
+

+
+
NAME
+
       stdarg - variable argument lists
+
+
SYNOPSIS
+
       #include <stdarg.h>
+
+       void va_start( va_list ap, last);
+       typeva_arg( va_list ap, type);
+       void va_end( va_list ap);
+
+
DESCRIPTION
+
       A  function  may  be called with a varying number of argu-
+       ments  of  varying  types.   The  include  file   stdarg.h
+       declares a type va_list and defines three macros for step-
+       ping through a list of arguments whose  number  and  types
+       are not known to the called function.
+
+       The called function must declare an object of type va_list
+       which is used by the macros va_start, va_arg, and  va_end.
+
+       The  va_start  macro  initializes ap for subsequent use by
+       va_arg and va_end, and must be called first.
+
+       The parameter last is  the  name  of  the  last  parameter
+       before  the variable argument list, i.e., the last parame-
+       ter of which the calling function knows the type.
+
+       Because the address of  this  parameter  is  used  in  the
+       va_start  macro,  it  should not be declared as a register
+       variable, or as a function or an array type.
+
+       The va_start macro returns no value.
+
+       The va_arg macro expands to an  expression  that  has  the
+       type  and  value  of  the  next argument in the call.  The
+       parameter ap is the va_list ap  initialized  by  va_start.
+       Each  call  to  va_arg  modifies  ap so that the next call
+       returns the next argument.  The parameter type is  a  type
+       name  specified so that the type of a pointer to an object
+       that has the specified type  can  be  obtained  simply  by
+       adding a * to type.
+
+       If there is no next argument, or if type is not compatible
+       with the type of the actual  next  argument  (as  promoted
+       according  to  the  default  argument  promotions), random
+       errors will occur.
+
+       The first use of  the  va_arg  macro  after  that  of  the
+       va_start  macro  returns the argument after last.  Succes-
+       sive invocations return the values of the remaining  argu-
+       ments.
+
+       The va_end macro handles a normal return from the function
+       whose variable argument list was initialized by  va_start.
+
+
+
+
BSD MANPAGE              29 November 1993                       1
+

+
+
+
+
+
STDARG(3)           Linux Programmer's Manual           STDARG(3)
+

+
+       The va_end macro returns no value.
+
+
EXAMPLES
+
       The  function  foo takes a string of format characters and
+       prints out the argument associated with each format  char-
+       acter based on the type.
+              void foo(char *fmt, ...)
+              {
+                   va_list ap;
+                   int d;
+                   char c, *p, *s;
+
+                   va_start(ap, fmt);
+                   while (*fmt)
+                        switch(*fmt++) {
+                        case 's':           /* string */
+                             s = va_arg(ap, char *);
+                             printf("string %s\n", s);
+                             break;
+                        case 'd':           /* int */
+                             d = va_arg(ap, int);
+                             printf("int %d\n", d);
+                             break;
+                        case 'c':           /* char */
+                             c = va_arg(ap, char);
+                             printf("char %c\n", c);
+                             break;
+                        }
+                   va_end(ap);
+              }
+
+
STANDARDS
+
       The  va_start,  va_arg,  and va_end macros conform to ANSI
+       C3.159-1989 (``ANSI C'').
+
+
COMPATIBILITY
+
       These macros are not compatible with the  historic  macros
+       they  replace.  A backward compatible version can be found
+       in the include file varargs.h.
+
+
BUGS
+
       Unlike the varargs macros, the stdarg macros do not permit
+       programmers  to  code  a function with no fixed arguments.
+       This problem generates work mainly when converting varargs
+       code  to stdarg code, but it also creates difficulties for
+       variadic functions that wish to pass all  of  their  argu-
+       ments on to a function that takes a va_list argument, such
+       as vfprintf(3).
+
+
+
+
+
+
+
+
+
+
BSD MANPAGE              29 November 1993                       2
+

+
+
+

+

+

+

+ + + + +
+Top + +Master Index + +Keywords + +Functions +
+
+

+

+ +This manual page was brought to you by mjl_man V-2.0 -- cgit v1.2.3-54-g00ecf