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I've always wondered where a single function such as printf(); can take in variable parameters and provide the right results. For example,

printf("Number is %d",a);

which has two parameters, and

printf("Numbers are %d and %d",a,b);

which has three variables. So, is there any possibilities for creating a user-defined function like these functions in C? If so, how can i do it? Thanks in advance.

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Interestingly, the C standard defines what variadic function declarations should look like, but no guidance in how to implement them.

The mechanics for accessing arguments to variadic functions are therefore implementation-dependent. GNU C provides this via stdarg.h.

  • There is a small example on the va_start man page. – ott-- Mar 9 '15 at 15:44
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    Actually, the macros in stdarg.h are the standard way for accessing arguments in variadic functions. The thing left open by the standard is how those macros should be implemented. – Bart van Ingen Schenau Mar 9 '15 at 16:57
  • (and the macros are guaranteed to be provided by a compliant compiler, so you don't need to worry about it - writing and using variadic functions is perfectly well-defined) – Thomas Mar 10 '15 at 0:55

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