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.\" @(#)varargs.3 6.4 (Berkeley) 5/14/90
.TH VARARGS 3 "May 14, 1990"
varargs \- variable argument lists
va_start(va_list ap, last);
va_arg(va_list ap, type);
A function may be called with a varying number of arguments of varying
declares a type (\fIva_list\fP) and defines three macros for stepping
through a list of arguments whose number and types are not known to
The called function must declare an object of type
which is used by the macros
and must be called first.
is the name of the last parameter before the variable argument list,
i.e. the last parameter of which the calling function knows the type.
Because the address of this parameter is used in the
macro, it should not be declared as a register variable, or as a
macro expands to an expression that has the type and value of the next
so that the next call returns the next argument.
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
If there is no next argument, or if
is not compatible with the type of the actual next argument
(as promoted according to the default argument promotions),
random errors will occur.
macro returns the argument after
Successive invocations return the values of the remaining
macro handles a normal return from the function whose variable argument
macros are ANSI C compatible.
compatible with the historic macros they replace.
A backward compatible version can be found in the include
takes a string of format characters and prints out the argument
associated with each format character based on the type.
printf("string %s\en", s);