Fixed bug #73163

3 files changed, 43 insertions, 29 deletions

diff --git a/NEWS b/NEWS
index 6bff08b6a0..674a6cb05c 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,8 @@ PHP                                                                        NEWS
     password_verify). (Anatol)
   . Fixed bug #73058 (crypt broken when salt is 'too' long). (Anatol)
   . Fixed bug #69579 (Invalid free in extension trait). (John Boehr)
+  . Fixed bug #73163 (PHP hangs if error handler throws while accessing undef
+    const in default value). (Nikita)
 
 - COM:
   . Fixed bug #73126 (Cannot pass parameter 1 by reference). (Anatol)
diff --git a/Zend/tests/bug73163.phpt b/Zend/tests/bug73163.phpt
new file mode 100644
index 0000000000..448d7f5959
--- /dev/null
+++ b/Zend/tests/bug73163.phpt
@@ -0,0 +1,22 @@
+--TEST--
+Bug #73163 (PHP hangs if error handler throws while accessing undef const in default value)
+--FILE--
+<?php
+
+function doSomething(string $value = UNDEFINED) {
+}
+
+set_error_handler(function($errno, $errstr) {
+    throw new Exception($errstr);
+});
+
+doSomething();
+
+?>
+--EXPECTF--
+Fatal error: Uncaught Exception: Use of undefined constant UNDEFINED - assumed 'UNDEFINED' in %s:%d
+Stack trace:
+#0 %s(%d): {closure}(%s)
+#1 %s(%d): doSomething()
+#2 {main}
+  thrown in %s on line %d
diff --git a/Zend/zend_execute_API.c b/Zend/zend_execute_API.c
index 1cbbc1a0a1..194f16df48 100644
--- a/Zend/zend_execute_API.c
+++ b/Zend/zend_execute_API.c
@@ -573,8 +573,6 @@ ZEND_API int zval_update_constant_ex(zval *p, zend_bool inline_change, zend_clas
 				ZVAL_EMPTY_STRING(p);
 			}
 		} else if (UNEXPECTED((const_value = zend_get_constant_ex(Z_STR_P(p), scope, Z_CONST_FLAGS_P(p))) == NULL)) {
-			char *actual = Z_STRVAL_P(p);
-
 			if (UNEXPECTED(EG(exception))) {
 				RESET_CONSTANT_VISITED(p);
 				return FAILURE;
@@ -584,46 +582,38 @@ ZEND_API int zval_update_constant_ex(zval *p, zend_bool inline_change, zend_clas
 				return FAILURE;
 			} else {
 				zend_string *save = Z_STR_P(p);
-				char *slash;
-				size_t actual_len = Z_STRLEN_P(p);
-				if ((Z_CONST_FLAGS_P(p) & IS_CONSTANT_UNQUALIFIED) && (slash = (char *)zend_memrchr(actual, '\\', actual_len))) {
-					actual = slash + 1;
-					actual_len -= (actual - Z_STRVAL_P(p));
-					if (inline_change) {
-						zend_string *s = zend_string_init(actual, actual_len, 0);
-						Z_STR_P(p) = s;
-						Z_TYPE_FLAGS_P(p) = IS_TYPE_REFCOUNTED | IS_TYPE_COPYABLE;
-					}
-				}
-				if (actual[0] == '\\') {
-					if (inline_change) {
-						memmove(Z_STRVAL_P(p), Z_STRVAL_P(p)+1, Z_STRLEN_P(p));
-						--Z_STRLEN_P(p);
-					} else {
-						++actual;
-					}
-					--actual_len;
-				}
 				if ((Z_CONST_FLAGS_P(p) & IS_CONSTANT_UNQUALIFIED) == 0) {
 					if (ZSTR_VAL(save)[0] == '\\') {
 						zend_throw_error(NULL, "Undefined constant '%s'", ZSTR_VAL(save) + 1);
 					} else {
 						zend_throw_error(NULL, "Undefined constant '%s'", ZSTR_VAL(save));
 					}
-					if (inline_change) {
-						zend_string_release(save);
-					}
 					RESET_CONSTANT_VISITED(p);
 					return FAILURE;
 				} else {
-					zend_error(E_NOTICE, "Use of undefined constant %s - assumed '%s'",  actual,  actual);
+					char *actual = Z_STRVAL_P(p);
+					size_t actual_len = Z_STRLEN_P(p);
+					char *slash = (char *) zend_memrchr(actual, '\\', actual_len);
+					if (slash) {
+						actual = slash + 1;
+						actual_len -= (actual - Z_STRVAL_P(p));
+					}
+
+					zend_error(E_NOTICE, "Use of undefined constant %s - assumed '%s'", actual, actual);
+					if (EG(exception)) {
+						RESET_CONSTANT_VISITED(p);
+						return FAILURE;
+					}
+
 					if (!inline_change) {
 						ZVAL_STRINGL(p, actual, actual_len);
 					} else {
-						Z_TYPE_INFO_P(p) = Z_REFCOUNTED_P(p) ?
-							IS_STRING_EX : IS_INTERNED_STRING_EX;
-						if (save && ZSTR_VAL(save) != actual) {
+						if (slash) {
+							ZVAL_STRINGL(p, actual, actual_len);
 							zend_string_release(save);
+						} else {
+							Z_TYPE_INFO_P(p) = Z_REFCOUNTED_P(p) ?
+								IS_STRING_EX : IS_INTERNED_STRING_EX;
 						}
 					}
 				}