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