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Date: Fri, 7 Mar 2008 12:17:13 +0200
Message-ID: <06B0D32C7A96544490D18AF653D6BDE50261886E@il-ex1.zend.net>
Thread-Topic: Patch for opcode caches
Thread-Index: AciAPF3aX6ZEvYErSGWi6AAar2KG7g==
To: "internals Mailing List" <internals@lists.php.net>
Cc: "Andi Gutmans" <andi@zend.com>,
	"Stas Malyshev" <stas@zend.com>,
	"phpxcache" <phpxcache@gmail.com>
Subject: Patch for opcode caches
From: dmitry@zend.com ("Dmitry Stogov")

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Hi,

The attached patch for PHP_5_3 is going to provide general solution to
control some aspects of PHP compilation. It is absolutely necessary for
all opcode caches to make cached scripts work exactly in the same way as
non-cached.
The problem occurs because early binding of inherited classes is not
possible for cached scripts. As result inheritance is handled in
run-time and classes might be created in wrong order. Most opcode caches
do some tricks to resolve this issue, but all of them fail to do it
right way.

The patch introduces CG(compiler_options), which is a set of compiler
flags that can be used by some extensions as opcode caches and
debuggers. Such flags change the process of compilation a bit.

For example to solve inherence early binding problem the opcode cache
need to compile file with additional flags=20

extension_compile_file() {
  ...
  orig_compiler_options =3D CG(compiler_options);
  CG(compiler_options) |=3D ZEND_COMPILE_IGNORE_INTERNAL_CLASSES |
ZEND_COMPILE_DELAYED_BINDING;
  orig_compile_file();
  CG(compiler_options) =3D orig_compiler_options;
  ...
}

And then during restoration from cache call
zend_do_delayed_early_binding().
This way even with cache all classes will be created exactly in the same
order.

The same CG(compiler_options) might be used to change other aspects of
compilation in the future.

The patch also optimizes ZEND_FETCH_CLASS+ZEND_ADD_INTERFACE opcodes
into single ZEND_ADD_INTERFACE, and makes verification of abstract
classes with interfaces only once.

I'm going to commit the patch on Monday or Tuesday.

Thanks. Dmitry.

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