Enable FFI+Opcache preload optimization

[lisachenko]

Loading/parsing definition of C headers in runtime is not good, also, ffi.enable is equal to preload by default, thus, to make this library active by default, preloading of C headers should be added.

Ideally, this requires some infrastructure support to activate FFI preloading.

• Wait for integration of preloading into composer [RFC] Preloading support composer/composer#7777
• Add cache-warming script that loads definition of headers during preload stage and compiles all library classes to be available by default to reduce class-loading time and compilation.
• Check long-running scripts (FPM, Standalone server) to ensure that there are no memory leaks and segfaults
• Wait for PHP7.4.2 to have a bug fix for: https://bugs.php.net/bug.php?id=78918
• For Windows platform, preloading is not available anymore since 7.4.2 Remove support for preloading on Windows php/php-src#4999

[lisachenko]

Preloading suffers from cyclic dependencies and could not preload classes that depend on each other. Let's say that class A contains a property with type B, which is initialized in constructor. Class B accepts link to the class A (aka parent instance) and stores it in his private typed property. Classes A and B are stored in different files.

In this case preload will fail...

[lisachenko]

There is a bug in preload + pointer casting that results in memory heap corruption: https://bugs.php.net/bug.php?id=78761

[lisachenko]

To make preloading work, all FFI calls should be only within the Core class, it will be preloaded by PHP, otherwise calls to FFI are restricted by the ffi.enable option.

[lisachenko]

Preload mode will only work in following releases of PHP7.4 (RC5 doesn't contain a patch for https://bugs.php.net/bug.php?id=78761)

[lisachenko]

Opcache preloading is broken, need at least PHP7.4.2 to include a bug fix for https://bugs.php.net/bug.php?id=78918

[lisachenko]

Windows doesn't support opcache preloading as of 7.4.2. Support was removed by @nikic in php/php-src@59c3dda due to ASLR restrictions for internal classes.

Additional details can be found here: php/php-src#4999

[nikic]

Note that you can use ffi.preload instead. It works on Windows.

[lisachenko]

Note that you can use ffi.preload instead. It works on Windows.

Thank you for replying, Nikita! I know about this configuration option, but my header file contains some macros which should be resolved in runtime accordind to platfrom, for example ZEND_FASTCALL, thus ffi.preload can't be used for this library.