Fixed bug #78589

Don't protect GC while destroying zvals. We may need to add GC
roots during this phase.

Author: nikic

Zend/tests/bug78589.phpt

@@ -0,0 +1,19 @@
+--TEST--
+Bug #78589: Memory leak with GC + __destruct()
+--FILE--
+<?php
+
+class Test {
+    public function __destruct() {}
+}
+
+$test = new Test;
+$test->foo = [&$test->foo];
+$ary = [&$ary, $test];
+unset($ary, $test);
+gc_collect_cycles();
+
+?>
+===DONE===
+--EXPECT--
+===DONE===

Zend/zend_gc.c

@@ -1549,7 +1549,6 @@ ZEND_API int zend_gc_collect_cycles(void)
 
 		/* Destroy zvals */
 		GC_TRACE("Destroying zvals");
-		GC_G(gc_protected) = 1;
 		current = GC_IDX2PTR(GC_FIRST_ROOT);
 		last = GC_IDX2PTR(GC_G(first_unused));
 		while (current != last) {
@@ -1600,7 +1599,6 @@ ZEND_API int zend_gc_collect_cycles(void)
 
 		GC_TRACE("Collection finished");
 		GC_G(collected) += count;
-		GC_G(gc_protected) = 0;
 		GC_G(gc_active) = 0;
 	}