From @dur-randir

Created by @dur-randir

commit eacbb37
Author​: Daniel Dragan <bulk88@​hotmail.com>
Date​: Fri Oct 31 03​:23​:17 2014 -0400

  free up CvPADLIST slot for XSUBs for future use

broke Devel​::FindRef for perls compiled with -DDEBUGGING with the
following assertion failure​:

perl​: FindRef.xs​:180​: XS_Devel__FindRef_find_​: Assertion
`!(((XPVCV*)({ void *_p = (((CV*)(sv))->sv_any); _p; }))->xcv_flags &
0x0008)' failed.

While a patch for Devel​::FindRef is quite trivial, I'd like to know,
are there any plans for CvPADLIST slots in XSUBs? Or isn't this
assertion obsolete now?

Flags:
    category=core
    severity=low

Site configuration information for perl 5.27.9:

Configured by dur-randir at Wed Jan 31 10:14:37 MSK 2018.

Summary of my perl5 (revision 5 version 27 subversion 9) configuration:
  Commit id: 577d3e04be845580196418dd9df1575e2cb4c0b6
  Platform:
    osname=darwin
    osvers=13.4.0
    archname=darwin-2level
    uname='darwin isengard.local 13.4.0 darwin kernel version 13.4.0:
mon jan 11 18:17:34 pst 2016; root:xnu-2422.115.15~1release_x86_64
x86_64 '
    config_args='-de -Dusedevel'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='cc'
    ccflags ='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.9
-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include
-DPERL_USE_SAFE_PUTENV'
    optimize='-O3'
    cppflags='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.9
-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion=''
    gccversion='4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.56)'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='cc'
    ldflags =' -mmacosx-version-min=10.9 -fstack-protector -L/usr/local/lib'
    libpth=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/6.0/lib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/lib
/usr/local/lib /usr/lib
    libs=-lpthread -lgdbm -ldbm -ldl -lm -lutil -lc
    perllibs=-lpthread -ldl -lm -lutil -lc
    libc=
    so=dylib
    useshrplib=false
    libperl=libperl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=bundle
    d_dlsymun=undef
    ccdlflags=' '
    cccdlflags=' '
    lddlflags=' -mmacosx-version-min=10.9 -bundle -undefined
dynamic_lookup -L/usr/local/lib -fstack-protector'



@INC for perl 5.27.9:
    lib
    /usr/local/lib/perl5/site_perl/5.27.9/darwin-2level
    /usr/local/lib/perl5/site_perl/5.27.9
    /usr/local/lib/perl5/5.27.9/darwin-2level
    /usr/local/lib/perl5/5.27.9


Environment for perl 5.27.9:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/dur-randir
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/Users/dur-randir/perlbrew/bin:/Users/dur-randir/perlbrew/perls/perl-5.22.1/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/texbin
    PERLBREW_BASHRC_VERSION=0.80
    PERLBREW_HOME=/Users/dur-randir/.perlbrew
    PERLBREW_MANPATH=/Users/dur-randir/perlbrew/perls/perl-5.22.1/man
    PERLBREW_PATH=/Users/dur-randir/perlbrew/bin:/Users/dur-randir/perlbrew/perls/perl-5.22.1/bin
    PERLBREW_PERL=perl-5.22.1
    PERLBREW_ROOT=/Users/dur-randir/perlbrew
    PERLBREW_VERSION=0.80
    PERL_BADLANG (unset)
    SHELL=/usr/local/bin/zsh

From @iabyn

On Mon, Apr 23, 2018 at 04​:52​:26AM -0700, Sergey Aleynikov wrote​:

commit eacbb37
Author​: Daniel Dragan <bulk88@​hotmail.com>
Date​: Fri Oct 31 03​:23​:17 2014 -0400

free up CvPADLIST slot for XSUBs for future use

broke Devel​::FindRef for perls compiled with -DDEBUGGING with the
following assertion failure​:

perl​: FindRef.xs​:180​: XS_Devel__FindRef_find_​: Assertion
`!(((XPVCV*)({ void *_p = (((CV*)(sv))->sv_any); _p; }))->xcv_flags &
0x0008)' failed.

While a patch for Devel​::FindRef is quite trivial, I'd like to know,
are there any plans for CvPADLIST slots in XSUBs? Or isn't this
assertion obsolete now?

I think Daniel would have to be the one to answer that question,
but in general, freeing up a slot in CV for potential future new uses
seems like a Good Thing, and so the assertion isn't obsolete.

(Since this change was in 5.22.0, I'm removing this ticket from the 5.28
blockers list.)

--
In England there is a special word which means the last sunshine
of the summer. That word is "spring".

The RT System itself - Status changed from 'new' to 'open'

From @bulk88

On Wed, 25 Apr 2018 03​:56​:42 -0700, davem wrote​:

On Mon, Apr 23, 2018 at 04​:52​:26AM -0700, Sergey Aleynikov wrote​:

commit eacbb37
Author​: Daniel Dragan <bulk88@​hotmail.com>
Date​: Fri Oct 31 03​:23​:17 2014 -0400

free up CvPADLIST slot for XSUBs for future use

broke Devel​::FindRef for perls compiled with -DDEBUGGING with the
following assertion failure​:

perl​: FindRef.xs​:180​: XS_Devel__FindRef_find_​: Assertion
`!(((XPVCV*)({ void *_p = (((CV*)(sv))->sv_any); _p; }))->xcv_flags &
0x0008)' failed.

While a patch for Devel​::FindRef is quite trivial, I'd like to know,
are there any plans for CvPADLIST slots in XSUBs? Or isn't this
assertion obsolete now?

I think Daniel would have to be the one to answer that question,
but in general, freeing up a slot in CV for potential future new uses
seems like a Good Thing, and so the assertion isn't obsolete.

(Since this change was in 5.22.0, I'm removing this ticket from the 5.28
blockers list.)

The assertion stops XS code from reading the "padlist" of an XSUB. There is no legitimate reason to read the "padlist" of an XSUB since XSUBs dont have any and the proc will probably SEGV. The padlist slot in XSUBs is used on unthreaded perl to pass a magic unique value that must round trip from the caller (IE libperl) of the XSUB, through the XSUB and back into libperl. This stops a scenario where an XS SO/DLL compiled against another perl version, is loaded by one perl (a PATH/CWD/PERL5DB/PERL5LIB/sitecustomize/@​INC/didnt delete "site/lib/auto" dir when upgrading perl/copy paste XS binaries mistake), and that XS SO/DLL then loads its original compiled against libperl into the process, and takes data structs from the caller libperl and passes them to the second libperl and there is a SEGV inside the 2nd libperl.

Fixing Devel​::FindRef is very easy. I did see the assert failure. But it was easy to fix.

  case SVt_PVCV​:
  {
  if(!CvISXSUB(sv)){<<<<<<<<<<<ADDD THIS
  PADLIST *padlist = CvPADLIST (sv);

  if (padlist)

and add a matching "}" after the end of "if (padlist)"'s "}".

This is more crude but also works.

  case SVt_PVCV​:
  {
  PADLIST *padlist = CvISXSUB(sv) ? NULL : CvPADLIST (sv);

  if (padlist)

--
bulk88 ~ bulk88 at hotmail.com

I was able to install Devel::FindRef on a debugging build of perl 5 blead today on each of Linux and FreeBSD.

Is this ticket closable? If not, what are the criteria which must be met in order to close it?

Thank you very much.
Jim Keenan

It can be closed.