Re: Is there any way to receive or pass an argument of C type "va_list"?

[T Lee Davidson <t.lee.davidson@xxxxxxxxx>]

On 4/4/24 18:01, Jussi Lahtinen wrote:
>     If not possible in Gambas, would a C program be able to process a va_list if it's pointer was passed to it?
>
>
> I'm a bit confused...  the example you sent (TestCommandical) used "va_list" to interact with Gambas side.
> What exactly do you mean?
>
>
> Jussi

No, it used a function that accepted variadic arguments to receive an integer, the array of structs, and OPTION_END. It's 
signature consisted of one parameter plus variadic parameters.

int parse_options (int count, ...)
{
  va_list ap;
  int ret;

  va_start (ap, count);
  ret = parse_options_va (count, ap);
  va_end (ap);
  return ret;
}

That function then slurped the variadic arguments into a va_list and passed that to parse_options_va().

int parse_options_va (int count, va_list ap)
{
  ...
}

I need to know if there is a way, or not, to pass or receive a va_list type directly to an external function or by a Gambas 
function (a callback). If not in Gambas, then perhaps I could write my own shared C library to do va_list conversions.

According to this /old/ StackOverflow post [1], "The va_list type is an array containing a single element of one structure 
containing the necessary information to implement the va_arg macro." I'm guessing that I could pass a pointer to a C function 
that would parse the va_list for me, but I am unsure about that.

[1] https://stackoverflow.com/questions/4958384/what-is-the-format-of-the-x86-64-va-list-structure


--
Lee

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