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36 .\" @(#)stdarg.3 8.1 (Berkeley) 6/5/93
43 .Nd variable argument lists
45 .Fd #include <stdarg.h>
47 .Fn va_start "va_list ap" last
49 .Fn va_arg "va_list ap" type
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
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 handles a normal return from the function whose variable argument
136 list was initialized by
141 macro returns no value.
145 takes a string of format characters and prints out the argument
146 associated with each format character based on the type.
147 .Bd -literal -offset indent
148 void foo(char *fmt, ...)
157 case 's': /* string */
158 s = va_arg(ap, char *);
159 printf("string %s\en", s);
163 printf("int %d\en", d);
166 c = va_arg(ap, char);
167 printf("char %c\en", c);
184 compatible with the historic macros they replace.
185 A backward compatible version can be found in the include
193 macros do not permit programmers to
194 code a function with no fixed arguments.
195 This problem generates work mainly when converting
200 but it also creates difficulties for variadic functions that
201 wish to pass all of their arguments on to a function