[perl #114566] Dealing With Freeded Memory Bugs in General in the Interp

# New Ticket Created by  bulk 88 
# Please include the string:  [perl #114566]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=114566 >




This is a bug report for perl from bulk88@hotmail.com,
generated with the help of perlbug 1.39 running under perl 5.12.3.


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[Please describe your issue here]

Please ignore the perl version in this ticket, I am talking about 5.17 here.

This is a continuation of the discussion/issues I brought up in RT #114496.

In some places, memory is freed, but the pointers are never set to NULL,
potentially causing freed memory bugs. For example S_nuke_stacks.
In other places, like in perl_destruct, Safefrees are followed by NULLing.

At the moment, there is the PERL_POISON flag. Mingw/VC Win32 builds with 
DEBUGGING do not currently turn on PERL_POISON. Some of the POSIX smokes,
such as http://www.nntp.perl.org/group/perl.daily-build.reports/2012/08/msg126373.html
do smoke with PERL_POISON on. I don't know if that is the smoke owner's choice
or its coming from the POSIX Perl build system.

So the issues are, should perl_destruct really be that aggressive in 
NULLing out on non-DEBUGGING builds or should it NULL often for perf reasons?

Should perl_destruct or S_nuke_stacks NULL out even more than before
in all build options?

Should Win32 Perls have PERL_POISON on with DEBUGGING/Cfg=Debug so
smoke tests will catch Win32 exclusive bugs such as #114496?

I noticed in RT #114496 that allocating a SV after perl_destruct "worked"
without any superficial errors (segvs/panics). Maybe that is a bug in and 
of itself.



[Please do not change anything below this line]
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---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.12.3:

Configured by gecko at Wed Feb  9 14:35:46 2011.

Summary of my perl5 (revision 5 version 12 subversion 3) configuration:
   
  Platform:
    osname=MSWin32, osvers=5.2, archname=MSWin32-x86-multi-thread
    uname=''
    config_args='undef'
    hint=recommended, useposix=true, d_sigaction=undef
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cl', ccflags ='-nologo -GF -W3 -MD -Zi -DNDEBUG -O1 -DWIN32 -D_CONSOLE -DNO_STRICT 

-DHAVE_DES_FCRYPT -DUSE_SITECUSTOMIZE -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS 

-DUSE_PERLIO -D_USE_32BIT_TIME_T -DPERL_MSVCRT_READFIX',
    optimize='-MD -Zi -DNDEBUG -O1',
    cppflags='-DWIN32'
    ccversion='15.0.30729', gccversion='', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=8
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='__int64', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='link', ldflags ='-nologo -nodefaultlib -debug -opt:ref,icf  

-libpath:"C:\Perl\lib\CORE"  -machine:x86'
    libpth=\lib
    libs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib  comdlg32.lib 

advapi32.lib shell32.lib ole32.lib oleaut32.lib  netapi32.lib uuid.lib ws2_32.lib mpr.lib 

winmm.lib  version.lib odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
    perllibs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib  comdlg32.lib 

advapi32.lib shell32.lib ole32.lib oleaut32.lib  netapi32.lib uuid.lib ws2_32.lib mpr.lib 

winmm.lib  version.lib odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
    libc=msvcrt.lib, so=dll, useshrplib=true, libperl=perl512.lib
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -debug -opt:ref,icf  

-libpath:"C:\Perl\lib\CORE"  -machine:x86'

Locally applied patches:
    ACTIVEPERL_LOCAL_PATCHES_ENTRY
    c6fbf28 [perl #71806] perldb does not setup %dbline with the shebang option -d
    1fd8fa4 Add Wolfram Humann to AUTHORS
    f120055 make string-append on win32 100 times faster
    a2a8d15 Define _USE_32BIT_TIME_T for VC6 and VC7
    007cfe1 Don't pretend to support really old VC++ compilers
    6d8f7c9 Get rid of obsolete PerlCRT.dll support
    d956618 Make Term::ReadLine::findConsole fall back to STDIN if /dev/tty can't be opened
    321e50c Escape patch strings before embedding them in patchlevel.h

---
@INC for perl 5.12.3:
    C:/Perl/site/lib
    C:/Perl/lib
    .

---
Environment for perl 5.12.3:
    CYGWIN=tty
    HOME (unset)
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    

PATH=C:\Perl\site\bin;C:\Perl\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:

\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin;C:\Program Files (x86)\Microsoft 

Visual Studio 9.0\VC;
    PERL_BADLANG (unset)
    PERL_JSON_BACKEND=JSON::XS
    PERL_YAML_BACKEND=YAML
    SHELL (unset)

 		 	   		  

• [perl #114566] Dealing With Freeded Memory Bugs in General in the Interp by bulk 88