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int printf(const char* fmt, ...);

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void using_var_args(int num_args, ...)
{
   va_list args;
   int i = 0;
   va_start(args, num); /* the first argument is a va_list. The second is the last non ... argument to a function */
   printf("the numbers passed are : ");
   for(;i < num_args;i++) {
       int cur = va_arg(args, int); /* the first argument is a va_list. The second is the type to return */
       printf("%d,", cur);
   }
   /* finally remember to call va_end */
  va_end(args);
}

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#include <stdarg.h>

...

void X86StackFrame::construct(ProcessorState &state,
                              uintptr_t returnAddress,
                              unsigned int nParams,
                              ...)
{
  // Obtain the stack pointer.
  uintptr_t *pStack = reinterpret_cast<uintptr_t*> (state.getStackPointer());
  
  // How many parameters do we need to push?
  // We push in reverse order but must iterate through the va_list in forward order,
  // so we decrement the stack pointer here.
  pStack -= nParams+1; // +1 for return address.
  uintptr_t *pStackLowWaterMark = pStack;
  
  *pStack++ = returnAddress;
  
  va_list list;
  va_start(list, nParams);
  
  for(int i = nParams-1; i >= 0; i--)
  {
    *pStack++ = va_arg(list, uintptr_t);
  }
  
  va_end(list);
  
  // Write the new stack pointer back.
  state.setStackPointer(reinterpret_cast<uintptr_t> (pStackLowWaterMark));
}

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#define va_start(v,l)   __builtin_va_start(v,l)
#define va_end(v)       __builtin_va_end(v)
#define va_arg(v,l)     __builtin_va_arg(v,l)

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#ifndef RC_INVOKED
#include_next<stdarg.h>
#endif

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/usr>find -iname 'stdarg.h'
./lib/gcc/i686-pc-mingw32/3.4.4/include/stdarg.h