var_dump() and debug_zval_dump() print the full anonymous class name with a raw NUL byte #25418

Description

Since 5ed6625 (#23143, %pS migration of ext/standard), var_dump() and debug_zval_dump() print the internal name of an anonymous class, including the NUL byte and the defining file path. PHP 8.5 printed class@anonymous.

The following code:

<?php
$o = new class { public $a = 1; private $p; };
var_dump($o);
print_r($o);

Resulted in this output (\0 is a raw NUL byte):

object(class@anonymous\0/in/test.php:2$0)#1 (2) {
  ["a"]=>
  int(1)
  ["p":"class@anonymous":private]=>
  NULL
}
class@anonymous Object
(
    [a] => 1
    [p:class@anonymous:private] =>
)

But I expected this output instead (as in PHP 8.5):

object(class@anonymous)#1 (2) {
  ["a"]=>
  int(1)
  ["p":"class@anonymous":private]=>
  NULL
}
class@anonymous Object
(
    [a] => 1
    [p:class@anonymous:private] =>
)

The commit changed php_printf("...object(%s)...", ZSTR_VAL(class_name)) to %pS, which prints the whole zend_string. The private property label (zend_unmangle_property_name() + %s) and print_r() still stop at the NUL, so the same dump now shows two different names for one class. The change is in 8.6.0RC6/RC7.

The full name is a deliberate consequence of treating NUL truncation as a bug (#23142), but for dumpers it was not discussed: #23143 had no review, the change is not in NEWS or UPGRADING, and labels and print_r() were left truncated. For 8.6 I suggest restoring %s for the two object headers in ext/standard/var.c (8.5 output); printing the full name consistently in dumps could be discussed for master. @DanielEScherzer, what do you think?

PHP Version

PHP 8.6.0RC7 (PHP-8.6 and master also affected)

Operating System

No response