Edit report at https://bugs.php.net/bug.php?id=46311&edit=1
ID: 46311
Comment by: olemar...@php.net
Reported by: anton at samba dot org
Summary: Pointer aliasing issue results in miscompile on
gcc4.4
Status: Assigned
Type: Bug
Package: Compile Failure
Operating System: RHEL5.2 / PowerPC64
PHP Version: 5.2.9
Assigned To: dmitry
Block user comment: N
Private report: N
New Comment:
The Gentoo patchset has been running with this for years now. Any reason why
this
has not been resolved yet?
Previous Comments:
------------------------------------------------------------------------
[2010-07-25 02:17:06] mabi at gentoo dot org
There are Gentoo downstream bugs related to this issue:
https://bugs.gentoo.org/show_bug.cgi?id=295682
https://bugs.gentoo.org/show_bug.cgi?id=329753
I'd love to see this fixed upstream, but will ship a custom patch to get this
more testing shortly.
------------------------------------------------------------------------
[2008-10-16 09:35:17] johan...@php.net
Dmitry, can you check this?
------------------------------------------------------------------------
[2008-10-16 05:54:12] anton at samba dot org
To clarify... the Zend code reads via zval *, not long *. The cut down test
case I submitted was simplified to use a long *.
------------------------------------------------------------------------
[2008-10-16 03:20:35] anton at samba dot org
I can't work out how to attach things in this tool. Here is a copy and paste of
it and a non whitespace damaged version can be found at:
http://ozlabs.org/~anton/junkcode/php_fix_aliasing.patch
Index: php-5.2.6/Zend/zend_execute.h
===================================================================
--- php-5.2.6.orig/Zend/zend_execute.h 2007-12-31 02:20:02.000000000 -0500
+++ php-5.2.6/Zend/zend_execute.h 2008-10-15 23:03:01.000000000 -0400
@@ -150,7 +150,7 @@
EG(argument_stack).top -= (delete_count+2);
while (--delete_count>=0) {
- zval *q = *(zval **)(--p);
+ zval *q = *(--p);
*p = NULL;
zval_ptr_dtor(&q);
}
------------------------------------------------------------------------
[2008-10-16 03:16:05] anton at samba dot org
Description:
------------
A recent checkout of gcc4.4 miscompiles php on PowerPC64. The following
function reads from p via long * and stores to p via void * which violates
aliasing rules:
static inline void zend_ptr_stack_clear_multiple(TSRMLS_D)
{
void **p = EG(argument_stack).top_element-2;
int delete_count = (int)(zend_uintptr_t) *p;
EG(argument_stack).top -= (delete_count+2);
while (--delete_count>=0) {
zval *q = *(zval **)(--p);
*p = NULL;
zval_ptr_dtor(&q);
}
EG(argument_stack).top_element = p;
}
More details can be found at:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37824
We can remove the (zval **) cast so that we read and write via void *p and fix
the aliasing issue. I will attach a patch.
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