PHP RFC: 64 bit platform improvements for PHP-NG

• Version: 0.9
• Date: 2014-05-20
• Author: Nikita Popov nikic@php.net
• Status: Draft

This RFC describes the decisions reached regarding improved 64bit support, following the discussion of the previous size_t_and_int64_next RFC.

The 64bit changes described in the following will be added to the phpng branch once it is more stable.

The following changes will be made:

• 64bit integers (in zvals and related areas) will be used on Win64 and other LLP64 platforms. This means that many current uses of long will be replaced with a type like zend_long which is 64bit large on all 64bit platforms.
• size_t will be used for string lengths in zend_string. This means that string sizes will be 64bit on 64bit platforms.
• 64bit sizes/integers may be used in some other places as well, as long as the usage does not significantly increase memory usage. E.g. file/stream offsets and ini settings like memory_limit should support 64bit numbers.

The following changes will not be made:

• Use of size_t for all lengths. In particular hashtables will always use 32bit lengths. Line numbers will be stored in a 32bit type. Special names (like argument or class names) will also use 32bit lengths, where possible.

The expected memory impact of these changes is around 1%. We are okay with that.

Unclear as of now: Will we be performing renames like IS_LONG to IS_INT along the way? I prefer not (Nikita).

Do you agree that 64bit platform improvements as described above should be implemented?