Zilog Z8F0130 - Manual (Page 448)

Appendix B. C Standard Library UM013037-1212
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A function can be called with a variable number of arguments of varying types. The Func-
tion Definitions parameter list contains one or more parameters. The rightmost parameter
plays a special role in the access mechanism and is designated parmN in this description.
Type
Variable Argument List Access Macros and Function
The va_start and va_arg macros described in this section are implemented as macros, not
as real functions. If
#undef is used to remove a macro definition and obtain access to a
real function, the behavior is undefined.
Functions
Standard Definitions
The following types and macros are defined in several headers referred to in the descrip-
tions of the functions declared in that header, as well as the common <
stddef.h > stan-
dard header.
Macros
Types
va_list An array type suitable for holding information needed by the macro va_arg
and the va_end function. The called function declares a variable (referred to
as ap in this section) having type va_list. The variable ap can be passed as
an argument to another function.
void va_start(va_list ap, parmN); Sets ap to the beginning of argument list.
type va_arg (va_list ap, type); Returns the next argument from list.
void va_end(va_list ap); Should mark the end of usage of ap (but has no
effect in Zilog implementation).
NULL Expands to a null pointer constant.
offsetof (type,
identifier) Expands to an integral constant expression that has type size_t
and provides the offset in bytes, from the beginning of a structure
designated by type to the member designated by identifier.
ptrdiff_t Signed integral type of the result of subtracting two pointers.