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Passing variable arguments to another function that accepts a variable argument list

Asked 2010-08-20T12:22:06.363
184

So I have 2 functions that both have similar arguments

void example(int a, int b, ...);
void exampleB(int b, ...);

Now example calls exampleB, but how can I pass along the variables in the variable argument list without modifying exampleB (as this is already used elsewhere too).

c++ variadic-functions
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Incidentally, many C implementations have an internal v?printf variation which IMHO should have been part of the C standard. The exact details vary, but a typical implementation will accept a struct containing a character-output function pointer and information saying what's supposed to happen. This allows printf, sprintf, and fprintf to all use the same 'core' mechanism. For example, vsprintf might be something like:

void s_out(PRINTF_INFO *p_inf, char ch)
{
  (*(p_inf->destptr)++) = ch;
  p_inf->result++;
}

int vsprintf(char *dest, const char *fmt, va_list args)
{
  PRINTF_INFO p_inf;
  p_inf.destptr = dest;
  p_inf.result = 0;
  p_inf.func = s_out;
  core_printf(&p_inf,fmt,args);
}

The core_printf function then calls p_inf->func for each character to be output; the output function can then send the characters to the console, a file, a string, or something else. If one's implementation exposes the core_printf function (and whatever setup mechanism it uses) one can extend it with all sorts of variations.

answered 2010-08-20T14:34:37.467

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