/* Need -0.0 for SvNVX to preserve IEEE FP "negative zero" because
   +0.0 + -0.0 => +0.0 but -0.0 + -0.0 => -0.0 */
#  define SvIVX(sv) (0 + ((XPVIV*) SvANY(sv))->xiv_iv)
#  define SvUVX(sv) (0 + ((XPVUV*) SvANY(sv))->xuv_uv)
#  define SvNVX(sv) (-0.0 + ((XPVNV*) SvANY(sv))->xnv_u.xnv_nv)

##</code><code>##

#ifdef __GNUC__
		/* to work round a gcc/x86 bug; don't use SvNV */
		anv.nv = sv_2nv(fromstr);
#else
		anv.nv = SvNV(fromstr);
#endif

##</code><code>##

Perl_sv_2nv_flags(pTHX_ SV *const sv, const I32 flags)
{
    dVAR;
    if (!sv)
	return 0.0;
    if (SvGMAGICAL(sv) || SvVALID(sv) || isREGEXP(sv)) {
	/* FBMs use the space for SvIVX and SvNVX for other purposes, and use
	   the same flag bit as SVf_IVisUV, so must not let them cache NVs.
	   Regexps have no SvIVX and SvNVX fields.  */
	const char *ptr;
	if (flags & SV_GMAGIC)
	    mg_get(sv);
	if (SvNOKp(sv))
	    return SvNVX(sv);

##</code><code>##

#! perl -slw
use strict; use Config;
use Inline C => Config => BUILD_NOISY => 1, CCFLAGS => $Config{ccflags}." -DDEBUG=1";
use Inline C => <<'END_C',  NAME => 'ICexample', CLEAN_AFTER_BUILD =>0;

static const unsigned __int64 i = 0x7ff0000000000001;

SV*get_snan() {
    SV *nv = newSVnv(0.0);
    *(unsigned __int64*)&( ((XPVNV*) SvANY(nv))->xnv_u.xnv_nv ) = i;
    return nv;
}

END_C

sub doubleToHex { scalar reverse unpack 'h16', pack 'd', $_[0] }

my $snan = get_snan();

printf "%f\n", $snan;

print doubleToHex( $snan );