#! 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*snan3() {
    // Allocate a new SvPV with some junk pv data
    SV *ret = newSVpvn( "JustJunk", 8 );

    // Assign the SNaN bit pattern directly to the NV field bypassing any dodgy macros
    *(unsigned __int64*)&( ( (XPVNV*)ret->sv_any )->xnv_u.xnv_nv ) = i;

    // Set the NOK flag
    SvNOK_on( ret );

    // Now point the PV pointer directly at the NV memory so we can access it
    // (the NV) from perl without going through pack 'd'/'F'
    // once again bypassing the API.
    (ret)->sv_u.svu_pv = (char*)&( ( (XPVNV*)ret->sv_any )->xnv_u.xnv_nv );

    // make it persist
    SvREFCNT_inc_void_NN( ret );

    // Make sure noone can mess with it.
    SvREADONLY( ret );
    return ret;
}


END_C
use Devel::Peek;
## Get an SNAN.
my $snan = snan3();

##Print its numeric value AND its bit pattern bypassing SVNV?()
printf "%f\n%x\n", $snan, unpack 'Q', $snan;

## Same thing as the printf '%x', unpack 'Q' above
## that *might* work on 32-bit that doesn't have Q
print scalar reverse unpack 'h*', $snan;

Dump( $snan );

__END__
C:\test>snan-ic.pl
...
Finished Build Compile Stage

1.#SNAN0
7ff0000000000001
7ff0000000000001
SV = PV(0xfbf60) at 0x157bc8
  REFCNT = 1
  FLAGS = (PADMY,NOK,POK,pNOK,pPOK)
  PV = 0x3db5d68 "\1\0\0\0\0\0\360\177"\0
  CUR = 8
  LEN = 16