使用`DEBUG_LEAKING_SCALARS`编译perl时,为什么不报告内存泄漏？

Question

我DEBUG_LEAKING_SCALARS按照这里描述编译perl

案例1
我按照此DOC测试内存泄漏报告:

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)

没有报道.

情况2
我甚至在我的XS sub中做了这件事.究竟:

#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();

链接到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)

也没有报道

案例3
我修复了模块Devel :: LeakTrace(The FIX):

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

也没有报道

案例4
我只发现Test :: LeakTrace完成它的工作:

$ 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

为什么在perl中内置工具报告没有泄漏？
我错了什么？如何使用DEBUG_LEAKING_SCALARS工具调试泄漏的内存？

Answer 1

实际上不是答案，而是戴夫·米切尔（Dave Mitchell）的答案：

DEBUG_LEAKING_SCALARS 的主要目的不是列出泄漏的标量
（！！）
，而是帮助跟踪通常与泄漏标量和引用计数问题相关的事情。它的两个主要特点是，它将 SV 分配从宏变为函数，以便您可以轻松附加断点；并且它向每个 SV 添加了检测，显示它的分配位置（如 Devel::Peek 显示的）。

但我不知道要调试什么，因为我不知道有什么东西泄漏了。就像上面描述的CASE 1 到3一样。我确信：

newSViv( 323 );

没有泄漏。

所以DEBUG_LEAKING_SCALARS 应该列出泄漏的标量

我还在 perl 提交历史中找到了这个评论：

-[ 24088] 作者： davem on 2005/03/28 21:38:44
- 日志：展开 -DDEBUG_LEAKING_SCALARS 来检测每个 SV 的创建

在我看来，这对于这项任务非常有用。