FFI::cast() from pointer returns new value instead of reference.

Description

Hi!
I'm also not sure it's a bug, but documentation says: FFI::cast() creates a new FFI\CData object, that references the same C data structure, but is associated with a different type.

The following code:

<?php

$val = FFI::new('char[8]');
FFI::memcpy($val, implode('', range('a', 'h')), 8);

var_dump($val);

$firstInt = FFI::cast('int32_t', $val);
var_dump($firstInt);
$firstInt->cdata = 0;
var_dump($val);

$secondInt = FFI::cast('int32_t', $val + 4);
var_dump($secondInt);
$secondInt->cdata = 0;
var_dump($val);

Resulted in this output:

object(FFI\CData:char[8])#1 (8) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
  [3]=>
  string(1) "d"
  [4]=>
  string(1) "e"
  [5]=>
  string(1) "f"
  [6]=>
  string(1) "g"
  [7]=>
  string(1) "h"
}
object(FFI\CData:int32_t)#2 (1) {
  ["cdata"]=>
  int(1684234849)
}
object(FFI\CData:char[8])#1 (8) {
  [0]=>
  string(1) ""
  [1]=>
  string(1) ""
  [2]=>
  string(1) ""
  [3]=>
  string(1) ""
  [4]=>
  string(1) "e"
  [5]=>
  string(1) "f"
  [6]=>
  string(1) "g"
  [7]=>
  string(1) "h"
}
object(FFI\CData:int32_t)#4 (1) {
  ["cdata"]=>
  int(721424396)
}
object(FFI\CData:char[8])#1 (8) {
  [0]=>
  string(1) ""
  [1]=>
  string(1) ""
  [2]=>
  string(1) ""
  [3]=>
  string(1) ""
  [4]=>
  string(1) "e"
  [5]=>
  string(1) "f"
  [6]=>
  string(1) "g"
  [7]=>
  string(1) "h"
}

But I expected this output instead:

object(FFI\CData:char[8])#1 (8) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
  [3]=>
  string(1) "d"
  [4]=>
  string(1) "e"
  [5]=>
  string(1) "f"
  [6]=>
  string(1) "g"
  [7]=>
  string(1) "h"
}
object(FFI\CData:int32_t)#2 (1) {
  ["cdata"]=>
  int(1684234849)
}
object(FFI\CData:char[8])#1 (8) {
  [0]=>
  string(1) ""
  [1]=>
  string(1) ""
  [2]=>
  string(1) ""
  [3]=>
  string(1) ""
  [4]=>
  string(1) "e"
  [5]=>
  string(1) "f"
  [6]=>
  string(1) "g"
  [7]=>
  string(1) "h"
}
object(FFI\CData:int32_t)#4 (1) {
  ["cdata"]=>
  int(721424396)
}
object(FFI\CData:char[8])#1 (8) {
  [0]=>
  string(1) ""
  [1]=>
  string(1) ""
  [2]=>
  string(1) ""
  [3]=>
  string(1) ""
  [4]=>
  string(1) ""
  [5]=>
  string(1) ""
  [6]=>
  string(1) ""
  [7]=>
  string(1) ""
}

PHP Version

PHP 8.1.1

Operating System

No response

首先运行提供的 PHP 8.1.1 FFI::cast() 复现代码，并比较从 $val 进行的指针转换与从 $val + 4 进行的转换。然后检查 FFI::cast() 的入口点以及相关测试（如果存在）。当文档中记录的共享引用行为对于两种转换都保持一致，或文档明确反映已验证的行为时，即视为完成。