Description:
------------
returning and directly using the result of a \FFI::cdef() function ends up in a void pointer.


php-src/ext/ffi/ffi.c:1990: zend_ffi_cdata_get_debug_info: Assertion `0' failed.
https://github.com/php/php-src/blob/9d7e03c325473024e54c864f0379efc1bbf03e72/ext/ffi/ffi.c#L1990


it's easy to reproduct with the same structs used here:

https://github.com/php/php-src/commit/05f3cd23ed61d800a861f2dd057ed56e783ea6f1#diff-3ea95b4dc57e34c882215bcc36f84551


i am not sure if this is a bug or a very consusing api limitation related to the livetime of zvals.




Test script:
---------------
// php code that SEGFAULTS
function ffi()
{
    return \FFI::cdef(
        file_get_contents(__DIR__ . '/example.h'),
        __DIR__ . '/lib.so'
    );
}

$res = ffi()->bug79096();
var_dump($res);


// php code that WORKS

// same as above
$ffi = ffi();
$res = $ffi->bug79096();

// c code
struct bug79096 bug79096(void)
{
  struct bug79096 b;

  b.a = 1;
  b.b = 1;
  return b;
}

// header 
struct bug79096 {
	uint64_t a;
	uint64_t b;
};

struct bug79096 bug79096(void);


Expected result:
----------------
object(FFI\CData:struct bug79096)#9 (2) {
  ["a"]=>
  int(1)
  ["b"]=>
  int(1)
}