Throw error for recursive comparison, instead of fatal (#14989)

I don't understand the rationale of fatal erroring here. It seems this should
properly unprotect the compared elements when returning up the stack.

Related to GH-14980

NEWS

@@ -4,6 +4,8 @@ PHP                                                                        NEWS
 
 - Core:
   . Fix GH-14978 (The xmlreader extension phpize build). (Peter Kokot)
+  . Throw Error exception when encountering recursion during comparison, rather
+    than fatal error. (ilutov)
 
 - BCMath:
   . Adjust bcround()'s $mode parameter to only accept the RoundingMode

UPGRADING

@@ -31,6 +31,8 @@ PHP 8.4 UPGRADE NOTES
   . The type of PHP_DEBUG and PHP_ZTS constants changed to bool.
   . The name of uploaded files and files created by the tempnam() function are
     now 13 bytes longer. Total length is platform-dependent.
+  . Encountering recursion during comparison now results in a Error exception,
+    rather than a fatal error.
 
 - DOM:
   . Added DOMNode::compareDocumentPosition() and DOMNode::DOCUMENT_POSITION_*

Zend/tests/bug63882.phpt

@@ -9,7 +9,12 @@ $testobj2 = new Test;
 $testobj1->x = $testobj1;
 $testobj2->x = $testobj2;
 
-var_dump($testobj1 == $testobj2);
+try {
+    var_dump($testobj1 == $testobj2);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
 ?>
---EXPECTF--
-Fatal error: Nesting level too deep - recursive dependency? in %sbug63882.php on line 9
+--EXPECT--
+Nesting level too deep - recursive dependency?

Zend/tests/recursive_array_comparison.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Comparison of a recursive array throws a catchable error
+--FILE--
+<?php
+$a = [&$a];
+try {
+    $a === [[]];
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    [[]] === $a;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($a === $a);
+?>
+--EXPECT--
+Nesting level too deep - recursive dependency?
+Nesting level too deep - recursive dependency?
+bool(true)

Zend/zend_hash.c

@@ -3180,7 +3180,8 @@ ZEND_API int zend_hash_compare(HashTable *ht1, HashTable *ht2, compare_func_t co
 	 * false recursion detection.
 	 */
 	if (UNEXPECTED(GC_IS_RECURSIVE(ht1))) {
-		zend_error_noreturn(E_ERROR, "Nesting level too deep - recursive dependency?");
+		zend_throw_error(NULL, "Nesting level too deep - recursive dependency?");
+		return ZEND_UNCOMPARABLE;
 	}
 
 	GC_TRY_PROTECT_RECURSION(ht1);

Zend/zend_object_handlers.c

@@ -1985,7 +1985,8 @@ ZEND_API int zend_std_compare_objects(zval *o1, zval *o2) /* {{{ */
 		 */
 		/* use bitwise OR to make only one conditional jump */
 		if (UNEXPECTED(Z_IS_RECURSIVE_P(o1))) {
-			zend_error_noreturn(E_ERROR, "Nesting level too deep - recursive dependency?");
+			zend_throw_error(NULL, "Nesting level too deep - recursive dependency?");
+			return ZEND_UNCOMPARABLE;
 		}
 		Z_PROTECT_RECURSION_P(o1);