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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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It is known as a variadic function. –  MichaelT Mar 9 at 14:50
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Related. –  Blrfl Mar 9 at 17:19

1 Answer 1

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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.

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There is a small example on the va_start man page. –  ott-- Mar 9 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 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 at 0:55

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