register_printf_specifier

[Geoff Winkless <geoff at defgeoff dot co dot uk>]

Hi

I'm working on a printf hook and the example code
https://sourceware.org/bugzilla/attachment.cgi?id=3874 is very useful;
however I'm a little confused by the xmm_ais function - it doesn't
seem to be checking info->user for any of the modifier values.

I was expecting something like:

static int
xmm_ais (const struct printf_info *info, size_t n, int *argtype, int *size)
{
  if (info->user & mod_v4f) {
    argtype[0] = pa_xmm;
    size[0] = sizeof (__m128);
    return 1;
  } else if (info->user & mod_v2d) {
    argtype[0] = pa_xmm;
    size[0]=sizeof(__m128d);
  } else if /* other mod_ checks here */ .... {

// now do the original sizes

  } else if (info->is_long_double) {
    argtype[0]=PA_DOUBLE | PA_FLAG_LONG_DOUBLE;
    size[0]=sizeof(long double);
  } else if (info->is_long) {
    argtype[0]=PA_DOUBLE;
    size[0]=sizeof(double);
  } else {
    argtype[0]=PA_FLOAT;
    size[0]=sizeof(float);
  }
  return 1;
}


Is this simply because the arginfo function doesn't need to be
accurate as long as the argtype is as large as the largest possible
expected value?

My question really is, can I rely on this behaviour going forward and
simply set size[0] to the maximum I expect?

Apologies if this is either the wrong place for this question or it's
answered elsewhere, I really have spent quite some time searching for
answers on the Right Way to use these hooks.

Thanks!

Geoff