minix/include/stdarg.h

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2005-04-21 16:53:53 +02:00
/* The <stdarg.h> header is ANSI's way to handle variable numbers of params.
* Some programming languages require a function that is declared with n
* parameters to be called with n parameters. C does not. A function may
* called with more parameters than it is declared with. The well-known
* printf function, for example, may have arbitrarily many parameters.
* The question arises how one can access all the parameters in a portable
* way. The C standard defines three macros that programs can use to
* advance through the parameter list. The definition of these macros for
* MINIX are given in this file. The three macros are:
*
* va_start(ap, parmN) prepare to access parameters
* va_arg(ap, type) get next parameter value and type
* va_end(ap) access is finished
*
* Ken Thompson's famous line from V6 UNIX is equally applicable to this file:
*
* "You are not expected to understand this"
*
*/
#ifndef _STDARG_H
#define _STDARG_H
#ifdef __GNUC__
/* The GNU C-compiler uses its own, but similar varargs mechanism. */
typedef char *va_list;
/* Amount of space required in an argument list for an arg of type TYPE.
* TYPE may alternatively be an expression whose type is used.
*/
#define __va_rounded_size(TYPE) \
(((sizeof (TYPE) + sizeof (int) - 1) / sizeof (int)) * sizeof (int))
#if __GNUC__ < 2
#ifndef __sparc__
#define va_start(AP, LASTARG) \
(AP = ((char *) &(LASTARG) + __va_rounded_size (LASTARG)))
#else
#define va_start(AP, LASTARG) \
(__builtin_saveregs (), \
AP = ((char *) &(LASTARG) + __va_rounded_size (LASTARG)))
#endif
void va_end (va_list); /* Defined in gnulib */
#define va_end(AP)
#define va_arg(AP, TYPE) \
(AP += __va_rounded_size (TYPE), \
*((TYPE *) (AP - __va_rounded_size (TYPE))))
#else /* __GNUC__ >= 2 */
#ifndef __sparc__
#define va_start(AP, LASTARG) \
(AP = ((char *) __builtin_next_arg ()))
#else
#define va_start(AP, LASTARG) \
(__builtin_saveregs (), AP = ((char *) __builtin_next_arg ()))
#endif
void va_end (va_list); /* Defined in libgcc.a */
#define va_end(AP)
#define va_arg(AP, TYPE) \
(AP = ((char *) (AP)) += __va_rounded_size (TYPE), \
*((TYPE *) ((char *) (AP) - __va_rounded_size (TYPE))))
#endif /* __GNUC__ >= 2 */
#else /* not __GNUC__ */
typedef char *va_list;
#define __vasz(x) ((sizeof(x)+sizeof(int)-1) & ~(sizeof(int) -1))
#define va_start(ap, parmN) ((ap) = (va_list)&parmN + __vasz(parmN))
#define va_arg(ap, type) \
(*((type *)((va_list)((ap) = (void *)((va_list)(ap) + __vasz(type))) \
- __vasz(type))))
#define va_end(ap)
#endif /* __GNUC__ */
#endif /* _STDARG_H */