Don't eliminate BIND_STATIC if it may cause undefined constant warning

Author: dstogov

ext/opcache/Optimizer/dce.c

@@ -242,6 +242,16 @@ static inline zend_bool may_have_side_effects(
 			}
 			return 0;
 		case ZEND_BIND_STATIC:
+			if (op_array->static_variables
+			 && (opline->extended_value & ZEND_BIND_REF) != 0) {
+				zval *value =
+					(zval*)((char*)op_array->static_variables->arData +
+						(opline->extended_value & ~ZEND_BIND_REF));
+				if (Z_TYPE_P(value) == IS_CONSTANT_AST) {
+					/* AST may contain undefined constants */
+					return 1;
+				}
+			}
 			return 0;
 		default:
 			/* For everything we didn't handle, assume a side-effect */

ext/opcache/tests/optimize_static_001.phpt

@@ -0,0 +1,19 @@
+--TEST--
+Keep BIND_STATIC when initial value refer to unresolved constants
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.optimization_level=-1
+--SKIPIF--
+<?php require_once('skipif.inc'); ?>
+--FILE--
+<?php
+function foo() {
+	static $a = UNDEFINED_CONST;
+}
+foo();
+?>
+OK
+--EXPECTF--
+Warning: Use of undefined constant UNDEFINED_CONST - assumed 'UNDEFINED_CONST' (this will throw an Error in a future version of PHP) in %s on line %d
+OK