zend_execute: Fix misleading UnhandledMatchError messages when exception_string_param_max_len=0

NEWS

@@ -18,6 +18,8 @@ PHP                                                                        NEWS
     non-printable characters in string literals). (nielsdos, WangYihang)
   . Add support for backtraces for fatal errors. (enorris)
   . Fixed bug GH-17442 (Engine UAF with reference assign and dtor). (nielsdos)
+  . Improved error message of UnhandledMatchError for
+    zend.exception_string_param_max_len=0. (timwolla)
 
 - Curl:
   . Added curl_multi_get_handles(). (timwolla)

Zend/tests/match/048.phpt

@@ -0,0 +1,42 @@
+--TEST--
+Match expression error messages (exception_string_param_max_len=0)
+--INI--
+zend.exception_string_param_max_len=0
+--FILE--
+<?php
+
+class Beep {}
+
+function test(mixed $var) {
+    try {
+        match($var) {};
+    } catch (UnhandledMatchError $e) {
+        print $e->getMessage() . PHP_EOL;
+    }
+}
+
+test(null);
+test(1);
+test(5.5);
+test(5.0);
+test("foo");
+test(true);
+test(false);
+test([1, 2, 3]);
+test(new Beep());
+// Testing long strings.
+test(str_repeat('e', 100));
+test(str_repeat("e\n", 100));
+?>
+--EXPECT--
+Unhandled match case NULL
+Unhandled match case 1
+Unhandled match case 5.5
+Unhandled match case 5.0
+Unhandled match case of type string
+Unhandled match case true
+Unhandled match case false
+Unhandled match case of type array
+Unhandled match case of type Beep
+Unhandled match case of type string
+Unhandled match case of type string

Zend/zend_execute.c

@@ -874,10 +874,12 @@ ZEND_COLD zend_never_inline void zend_magic_get_property_type_inconsistency_erro
 
 ZEND_COLD void zend_match_unhandled_error(const zval *value)
 {
+	zend_long max_len = EG(exception_string_param_max_len);
 	smart_str msg = {0};
 	if (
 		EG(exception_ignore_args)
-		|| smart_str_append_zval(&msg, value, EG(exception_string_param_max_len)) != SUCCESS
+		|| (Z_TYPE_P(value) == IS_STRING && max_len == 0)
+		|| smart_str_append_zval(&msg, value, max_len) != SUCCESS
 	) {
 		smart_str_appendl(&msg, "of type ", sizeof("of type ")-1);
 		smart_str_appends(&msg, zend_zval_type_name(value));