Missing header files

I want to use variable number of arguments for functions.

I wrote a sample application for this using va_list, va_start etc.

But It showd following errors :
i) va_list is out of scope/ not declared.
ii) Reference to ‘va_start’ has no corresponding prototype.

I found that stdarg.lib or stdarg.h (which we use for normal C program ) file is not available under “LIB” directory.

So which header file or library is to be #use 'd to run the program.

Please suggest solution/comments to the problem.

Thanks in advance.