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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 $
40 .Nd variable argument lists
44 .Fn va_start "va_list ap" last
46 .Fn va_arg "va_list ap" type
48 .Fn va_copy "va_list dest" "va_list src"
50 .Fn va_end "va_list ap"
52 A function may be called with a varying number of arguments of varying
58 and defines three macros for stepping
59 through a list of arguments whose number and types are not known to
62 The called function must declare an object of type
64 which is used by the macros
79 and must be called first.
83 is the name of the last parameter before the variable argument list,
84 i.e., the last parameter of which the calling function knows the type.
86 Because the address of this parameter is used in the
88 macro, it should not be declared as a register variable, or as a
89 function or an array type.
93 macro returns no value.
97 macro expands to an expression that has the type and value of the next
109 so that the next call returns the next argument.
112 is a type name specified so that the type of a pointer to an
113 object that has the specified type can be obtained simply by
118 If there is no next argument, or if
120 is not compatible with the type of the actual next argument
121 (as promoted according to the default argument promotions),
122 random errors will occur.
126 macro after that of the
128 macro returns the argument after
130 Successive invocations return the values of the remaining
135 macro copies a variable argument list, previously initialized by
141 The state is preserved such that it is equivalent to calling
143 with the same second argument used with
147 the same number of times as called with
152 macro returns no value.
156 macro handles a normal return from the function whose variable argument
157 list was initialized by
162 macro returns no value.
166 takes a string of format characters and prints out the argument
167 associated with each format character based on the type.
168 .Bd -literal -offset indent
169 void foo(char *fmt, ...)
178 case 's': /* string */
179 s = va_arg(ap, char *);
180 printf("string %s\en", s);
184 printf("int %d\en", d);
187 /* Note: char is promoted to int. */
189 printf("char %c\en", c);
198 compatible with the historic macros they replace.
213 macros do not permit programmers to
214 code a function with no fixed arguments.
215 This problem generates work mainly when converting
220 but it also creates difficulties for variadic functions that
221 wish to pass all of their arguments on to a function