Moreover when you do:

/* Something Perl shouldn't free */
static char s[4] = "\x11\x11\x11\x11";

SV* fetch() {
   SV* sv = newSV_type(SVt_PV);
   SvPV_set(sv, s);
   SvPOK_on(sv);
   SvLEN_set(sv, 0);
   SvCUR_set(sv, 4);
   return newRV_noinc(sv);
}
[download]

The Devel::Peek::Dump shows:

SV = IV(0x8add89c) at 0x8add8a0
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  RV = 0x8abf520
  SV = PV(0x8abc700) at 0x8abf520
    REFCNT = 1
    FLAGS = (POK,pPOK)
    PV = 0xb7d0e06c "\21\21\21\21"
    CUR = 4
    LEN = 0
[download]

However for my set of

 
          SV * sv = newSV_type(SVt_PV);
          SvPV_set(sv, surface->pixels);
          SvPOK_on(sv);
          SvLEN_set(sv, 0);
          SvCUR_set(sv, surface->format->BytesPerPixel * surface->w * 
+surface->h);
          RETVAL = newRV_noinc(sv);
[download]

The surface Devel::Peek::Dump has different types:

SV = RV(0x142b330) at 0x142b324
 REFCNT = 1
 FLAGS = (TEMP,ROK) 
 RV = 0x3e90fc
 SV = PV(0x1287a9c) at 0x3e90fc
   REFCNT = 1
   FLAGS = (POK,pPOK)
   PV = 0xcea408 "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
   CUR = 16
   LEN = 0
[download]

Why is the type a RV and not IV?