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Thread-Topic: [PHP-DEV] Re: PHP 5.6 static access valgrind issue
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Date: Thu, 10 Nov 2016 08:05:38 +0000
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Subject: Re: [PHP-DEV] Re: PHP 5.6 static access valgrind issue
From: dmitry@zend.com (Dmitry Stogov)

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On Nov 9, 2016 20:45, Derick Rethans <derick@php.net> wrote:
>
> On Wed, 9 Nov 2016, Nikita Popov wrote:
>
> > On Wed, Nov 9, 2016 at 4:09 PM, Derick Rethans <derick@php.net> wrote:
> >
> > > On Wed, 9 Nov 2016, Christoph M. Becker wrote:
> > >
> > > > On 09.11.2016 at 15:21, Derick Rethans wrote:
> > >
> > > <snip>
> > >
> > > > > And running it with "valgrind php -n index.php", produces:
> > > > >
> > > > >     root@debian-8-64bit:/home/derick/xdebug-issue-1185# valgrind =
php -n index.php
> > > > >     =3D=3D760=3D=3D Memcheck, a memory error detector
> > > > >     =3D=3D760=3D=3D Copyright (C) 2002-2013, and GNU GPL'd, by Ju=
lian Seward et al.
> > > > >     =3D=3D760=3D=3D Using Valgrind-3.10.0 and LibVEX; rerun with =
-h for copyright info
> > > > >     =3D=3D760=3D=3D Command: php -n index.php
> > > > >     =3D=3D760=3D=3D
> > > > >     =3D=3D760=3D=3D Conditional jump or move depends on uninitial=
ised value(s)
> > > > >     =3D=3D760=3D=3D    at 0x797992: zend_std_get_static_method (z=
end_object_handlers.c:1261)
> > > > >     =3D=3D760=3D=3D    by 0x7B66FE: ZEND_INIT_STATIC_METHOD_CALL_=
SPEC_CONST_CONST_HANDLER (zend_vm_execute.h:3887)
> > > > >     =3D=3D760=3D=3D    by 0x7A379F: execute_ex (zend_vm_execute.h=
:363)
> > > > >     =3D=3D760=3D=3D    by 0x76E2AF: zend_execute_scripts (zend.c:=
1341)
> > > > >     =3D=3D760=3D=3D    by 0x70CC87: php_execute_script (main.c:26=
13)
> > > > >     =3D=3D760=3D=3D    by 0x81A990: do_cli (php_cli.c:998)
> > > > >     =3D=3D760=3D=3D    by 0x431996: main (php_cli.c:1382)
> > > > >     =3D=3D760=3D=3D
> > >
> > > > zend_std_get_static_method() declares use_heap[1] (if there's suppo=
rt
> > > > for alloca), but doesn't initialize it with SET_ALLOCA_FLAG()[2].  =
It
> > > > seems to me that ALLOCA_FLAG()[3] should be defined like so:
> > > >
> > > >   # define ALLOCA_FLAG(name) \
> > > >     zend_bool name =3D 0;
> > >
> > > That sounds about right - Dmitry, Nikita?
> >
> > This shouldn't be a problem. alloca is only used in the !key branches, =
in
> > which case the flag is initialized by do_alloca.
>
> However, it is a problem as my valgrind note says. However, I wouldn't
> be surprised if this was a (Debian) GCC bug. I can't reproduce this when
> I change -O2 to -O0 in the Makefile.
>
> In the past, I have found a similar issue in Xdebug, where it was really
> something Xdebug was doing wrong, but in a very vague way
> (https://github.com/xdebug/xdebug/commit/c36ea38141cb9403ff4bf72602fcf4ae=
62e5ba1e).
>
> However, right now, it's a bug with this GCC version.
>

This is possible.
In this backtracked "key" has to be not NULL, and the line 1261 shouldn't b=
e reached at all.

Thanks. Dmitry.

> cheers,
> Derick
>
> --
> https://derickrethans.nl | https://xdebug.org | https://dram.io
> Like Xdebug? Consider a donation: https://xdebug.org/donate.php
> twitter: @derickr and @xdebug

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