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In computer programming, a variable argument macro, or varargs macro, is a feature of the C programming language which permits preprocessor macros to accept a varying number of arguments. Their syntax is similar to that of variable argument functions: The special sequence "..." is used to indicate one or more arguments. The identifier __VA_ARGS__ in the macro definition is then substituted by these arguments.
For example, if a printf-like function dprintf() were desired, which would pass the file and line number from which it was called as arguments, the following macro might be used:
void realdprintf (char const *file, int line, char const *fmt, ...);
#define dprintf(...) realdprintf(__FILE__, __LINE__, __VA_ARGS__);
dprintf() could then be called as:
dprintf("Hello, world");
/* Expands to:
* realdprintf(__FILE__, __LINE__, "Hello, world");
*/
or:
dprintf("%d + %d = %d", 2, 2, 5);
/* Expands to:
* realdprintf(__FILE__, __LINE__, "%d + %d = %d", 2, 2, 5);
*/
Variable argument macros are supported in the C language since ISO/IEC 9899:1999, C99.
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