Why is a memory leak not reported when compiling perl with `DEBUG_LEAKING_SCALARS`?

Question

I compile perl with DEBUG_LEAKING_SCALARSas described here

CASE 1
I follow this DOC to check for memory leak:

env PERL_DESTRUCT_LEVEL=2 valgrind perl -e '@x; $x[0]=\@x'
==7216== Memcheck, a memory error detector
==7216== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==7216== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==7216== Command: perl -e @x;\ $x[0]=\\@x
==7216== 
==7216== 
==7216== HEAP SUMMARY:
==7216==     in use at exit: 0 bytes in 0 blocks
==7216==   total heap usage: 1,310 allocs, 1,310 frees, 171,397 bytes allocated
==7216== 
==7216== All heap blocks were freed -- no leaks are possible
==7216== 
==7216== For counts of detected and suppressed errors, rerun with: -v
==7216== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Nothing is reported.

CASE 2
I even in my approach XS this thing . Exactly:

#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include "XSUtils.h"
#include "ppport.h"

void
call_perl() {
    SV *sv;
    sv =  sv_2mortal( newSVpv( "XS::Utils::hello", 0 ) );

    newSViv( 323 );     //<<<< SHOULD LEAK
    printf( "Hi 3\n" );

    ENTERSCOPE;
    CALLPERL( sv , G_DISCARD|G_NOARGS );
    LEAVESCOPE;
}

MODULE = XS::Utils                    PACKAGE = XS::Utils

void
test()
    CODE:
        call_perl();

Link to REPO

$ env PERL_DESTRUCT_LEVEL=2 valgrind perl -Iblib/arch/ -Iblib/lib -MXS::Utils -e 'XS::Utils::test()' 
==7308== Memcheck, a memory error detector
==7308== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==7308== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==7308== Command: perl -Iblib/arch/ -Iblib/lib -MXS::Utils -e XS::Utils::test()
==7308== 
Hi 3
Hello
==7308== 
==7308== HEAP SUMMARY:
==7308==     in use at exit: 1,502 bytes in 5 blocks
==7308==   total heap usage: 12,876 allocs, 12,871 frees, 1,945,298 bytes allocated
==7308== 
==7308== LEAK SUMMARY:
==7308==    definitely lost: 0 bytes in 0 blocks
==7308==    indirectly lost: 0 bytes in 0 blocks
==7308==      possibly lost: 0 bytes in 0 blocks
==7308==    still reachable: 1,502 bytes in 5 blocks
==7308==         suppressed: 0 bytes in 0 blocks
==7308== Rerun with --leak-check=full to see details of leaked memory
==7308== 
==7308== For counts of detected and suppressed errors, rerun with: -v
==7308== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Nothing reported

CASE 3
I am fixing the Devel :: LeakTrace module ( FIX )

$ perl -MDevel::LeakTrace -Iblib/arch/ -Iblib/lib -MXS::Utils -e 'XS::Utils::test()' 
Hi 3
Hello

Nothing reported

CASE 4
I found Test :: LeakTrace to do my job:

$ perl -MTest::LeakTrace::Script=-verbose -Iblib/arch/ -Iblib/lib -MXS::Utils -e 'XS::Utils::test()' 
Hi 3
Hello
leaked SCALAR(0x208e1c0) from -e line 1.
ALLOCATED at -e:1 by entersub (parent 0x0); serial 9642
SV = IV(0x208e1b0) at 0x208e1c0
  REFCNT = 1
  FLAGS = (IOK,pIOK)
  IV = 323

Why doesn't the perl native tool report a leak?
What am I wrong? How to debug a memory leak with a tool DEBUG_LEAKING_SCALARS?

Answer 1

, :

DEBUG_LEAKING_SCALARS -
(!!)
, refcount . : SV , ; SV, ( Devel:: Peek).

, , , - . CASE 1 3, . , :

newSViv( 323 );

.

, DEBUG_LEAKING_SCALARS

perl commit:

- [24088] : davem 2005/03/28 21:38:44
- Log: expand -DDEBUG_LEAKING_SCALARS SV

.