Variadic functions are functions (e.g. printf) which take a variable number of arguments.
The declaration of a variadic function uses an ellipsis as the last parameter, e.g. int printf(const char* format, ...);. See variadic arguments for additional detail on the syntax and automatic argument conversions.
Accessing the variadic arguments from the function body uses the following library facilities:
Macros |
|
Defined in header <stdarg.h> |
|
|---|---|
| enables access to variadic function arguments (function macro) |
|
| accesses the next variadic function argument (function macro) |
|
|
(C99) | makes a copy of the variadic function arguments (function macro) |
| ends traversal of the variadic function arguments (function macro) |
|
Type |
|
| holds the information needed by va_start, va_arg, va_end, and va_copy (typedef) |
|
Print values of different types.
#include <stdio.h>
#include <stdarg.h>
void simple_printf(const char* fmt, ...)
{
va_list args;
va_start(args, fmt);
while (*fmt != '\0') {
if (*fmt == 'd') {
int i = va_arg(args, int);
printf("%d\n", i);
} else if (*fmt == 'c') {
// A 'char' variable will be promoted to 'int'
// A character literal in C is already 'int' by itself
int c = va_arg(args, int);
printf("%c\n", c);
} else if (*fmt == 'f') {
double d = va_arg(args, double);
printf("%f\n", d);
}
++fmt;
}
va_end(args);
}
int main(void)
{
simple_printf("dcff", 3, 'a', 1.999, 42.5);
}Output:
3 a 1.999000 42.50000
| C++ documentation for Variadic functions |
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