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32 .\" @(#)stdarg.3 8.1 (Berkeley) 6/5/93
33 .\" $FreeBSD: src/share/man/man3/stdarg.3,v 1.15 2005/01/21 08:36:36 ru Exp $
34 .\" $DragonFly: src/share/man/man3/stdarg.3,v 1.3 2005/11/20 11:05:44 swildner Exp $
41 .Nd variable argument lists
45 .Fn va_start "va_list ap" last
47 .Fn va_arg "va_list ap" type
49 .Fn va_copy "va_list dest" "va_list src"
51 .Fn va_end "va_list ap"
53 A function may be called with a varying number of arguments of varying
59 and defines three macros for stepping
60 through a list of arguments whose number and types are not known to
63 The called function must declare an object of type
65 which is used by the macros
80 and must be called first.
84 is the name of the last parameter before the variable argument list,
85 i.e., the last parameter of which the calling function knows the type.
87 Because the address of this parameter is used in the
89 macro, it should not be declared as a register variable, or as a
90 function or an array type.
94 macro returns no value.
98 macro expands to an expression that has the type and value of the next
110 so that the next call returns the next argument.
113 is a type name specified so that the type of a pointer to an
114 object that has the specified type can be obtained simply by
119 If there is no next argument, or if
121 is not compatible with the type of the actual next argument
122 (as promoted according to the default argument promotions),
123 random errors will occur.
127 macro after that of the
129 macro returns the argument after
131 Successive invocations return the values of the remaining
136 macro copies a variable argument list, previously initialized by
142 The state is preserved such that it is equivalent to calling
144 with the same second argument used with
148 the same number of times as called with
153 macro returns no value.
157 macro handles a normal return from the function whose variable argument
158 list was initialized by
163 macro returns no value.
167 takes a string of format characters and prints out the argument
168 associated with each format character based on the type.
169 .Bd -literal -offset indent
170 void foo(char *fmt, ...)
179 case 's': /* string */
180 s = va_arg(ap, char *);
181 printf("string %s\en", s);
185 printf("int %d\en", d);
188 /* Note: char is promoted to int. */
190 printf("char %c\en", c);
199 compatible with the historic macros they replace.
200 A backward compatible version can be found in the include
217 macros do not permit programmers to
218 code a function with no fixed arguments.
219 This problem generates work mainly when converting
224 but it also creates difficulties for variadic functions that
225 wish to pass all of their arguments on to a function