| 1 | /* The <stdarg.h> header is ANSI's way to handle variable numbers of params.
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| 2 | * Some programming languages require a function that is declared with n
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| 3 | * parameters to be called with n parameters. C does not. A function may
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| 4 | * called with more parameters than it is declared with. The well-known
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| 5 | * printf function, for example, may have arbitrarily many parameters.
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| 6 | * The question arises how one can access all the parameters in a portable
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| 7 | * way. The C standard defines three macros that programs can use to
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| 8 | * advance through the parameter list. The definition of these macros for
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| 9 | * MINIX are given in this file. The three macros are:
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| 10 | *
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| 11 | * va_start(ap, parmN) prepare to access parameters
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| 12 | * va_arg(ap, type) get next parameter value and type
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| 13 | * va_end(ap) access is finished
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| 14 | *
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| 15 | * Ken Thompson's famous line from V6 UNIX is equally applicable to this file:
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| 16 | *
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| 17 | * "You are not expected to understand this"
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| 18 | *
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| 19 | */
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| 20 |
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| 21 | #ifndef _STDARG_H
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| 22 | #define _STDARG_H
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| 23 |
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| 24 | #ifdef __GNUC__
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| 25 | /* The GNU C-compiler uses its own, but similar varargs mechanism. */
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| 26 |
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| 27 | typedef char *va_list;
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| 28 |
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| 29 | /* Amount of space required in an argument list for an arg of type TYPE.
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| 30 | * TYPE may alternatively be an expression whose type is used.
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| 31 | */
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| 32 |
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| 33 | #define __va_rounded_size(TYPE) \
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| 34 | (((sizeof (TYPE) + sizeof (int) - 1) / sizeof (int)) * sizeof (int))
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| 35 |
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| 36 | #if __GNUC__ < 2
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| 37 |
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| 38 | #ifndef __sparc__
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| 39 | #define va_start(AP, LASTARG) \
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| 40 | (AP = ((char *) &(LASTARG) + __va_rounded_size (LASTARG)))
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| 41 | #else
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| 42 | #define va_start(AP, LASTARG) \
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| 43 | (__builtin_saveregs (), \
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| 44 | AP = ((char *) &(LASTARG) + __va_rounded_size (LASTARG)))
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| 45 | #endif
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| 46 |
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| 47 | void va_end (va_list); /* Defined in gnulib */
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| 48 | #define va_end(AP)
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| 49 |
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| 50 | #define va_arg(AP, TYPE) \
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| 51 | (AP += __va_rounded_size (TYPE), \
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| 52 | *((TYPE *) (AP - __va_rounded_size (TYPE))))
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| 53 |
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| 54 | #else /* __GNUC__ >= 2 */
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| 55 |
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| 56 | #ifndef __sparc__
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| 57 | #define va_start(AP, LASTARG) \
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| 58 | (AP = ((char *) __builtin_next_arg ()))
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| 59 | #else
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| 60 | #define va_start(AP, LASTARG) \
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| 61 | (__builtin_saveregs (), AP = ((char *) __builtin_next_arg ()))
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| 62 | #endif
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| 63 |
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| 64 | void va_end (va_list); /* Defined in libgcc.a */
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| 65 | #define va_end(AP)
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| 66 |
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| 67 | #define va_arg(AP, TYPE) \
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| 68 | (AP = ((char *) (AP)) += __va_rounded_size (TYPE), \
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| 69 | *((TYPE *) ((char *) (AP) - __va_rounded_size (TYPE))))
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| 70 |
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| 71 | #endif /* __GNUC__ >= 2 */
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| 72 |
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| 73 | #else /* not __GNUC__ */
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| 74 |
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| 75 | typedef char *va_list;
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| 76 |
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| 77 | #define __vasz(x) ((sizeof(x)+sizeof(int)-1) & ~(sizeof(int) -1))
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| 78 |
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| 79 | #define va_start(ap, parmN) ((ap) = (va_list)&parmN + __vasz(parmN))
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| 80 | #define va_arg(ap, type) \
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| 81 | (*((type *)((va_list)((ap) = (void *)((va_list)(ap) + __vasz(type))) \
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| 82 | - __vasz(type))))
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| 83 | #define va_end(ap)
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| 84 |
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| 85 | #endif /* __GNUC__ */
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| 86 |
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| 87 | #endif /* _STDARG_H */
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