Handle exceptions in casting more gracefully.

This fixes bug #26166

Zend/tests/bug26166.phpt

@@ -0,0 +1,67 @@
+--TEST--
+Bug #26166: __toString() crash when no values returned
+--FILE--
+<?php
+class Foo
+{
+    function __toString()
+    {
+        return "Hello World!\n";
+    }
+}
+
+class Bar
+{
+    private $obj;
+
+    function __construct()
+    {
+        $this->obj = new Foo();
+    }
+
+    function __toString()
+    {
+        return $this->obj->__toString();
+    }
+}
+
+$o = new Bar;
+echo $o;
+
+echo "===THROW===\n";
+
+class Error 
+{
+	function __toString() {
+		throw new Exception("This is an error!");
+	}
+}
+
+$o = new Error;
+try {
+	echo $o;
+}
+catch (Exception $e) {
+	echo "Got the exception\n";
+}
+
+echo "===NONE===\n";
+
+class None
+{
+	function __toString() {
+	}
+}
+
+$o = new None;
+echo $o;
+
+?>
+===DONE===
+--EXPECTF--
+Hello World!
+===THROW===
+Got the exception
+===NONE===
+
+Fatal error: Method none::__toString() must return a string value in %sbug26166.php on line %d

Zend/zend.c

@@ -230,6 +230,12 @@ ZEND_API void zend_make_printable_zval(zval *expr, zval *expr_copy, int *use_cop
 				if (expr->value.obj.handlers->cast_object(expr, expr_copy, IS_STRING, 0 TSRMLS_CC) == SUCCESS) {
 					break;
 				}
+				if (EG(exception)) {
+					zval_dtor(expr_copy);
+					expr_copy->value.str.len = 0;
+					expr_copy->value.str.val = empty_string;
+					break;
+				}
 			}
 			expr_copy->value.str.val = (char *) emalloc(sizeof("Object id #")-1 + MAX_LENGTH_OF_LONG);
 			expr_copy->value.str.len = sprintf(expr_copy->value.str.val, "Object id #%ld", (long)expr->value.obj.handle);

Zend/zend_object_handlers.c

@@ -869,8 +869,13 @@ int zend_std_cast_object(zval *readobj, zval *writeobj, int type, int should_fre
 	case IS_STRING:
 		ZVAL_STRING(&fname, "__tostring", 0);
 		if (call_user_function_ex(NULL, &readobj, &fname, &retval, 0, NULL, 0, NULL TSRMLS_CC) == SUCCESS) {
-			if (Z_TYPE_P(retval) != IS_STRING) {
-				zend_error(E_ERROR, "Method %s::__toString() must return a string value", Z_OBJCE_P(readobj)->name);
+			if (retval) {
+				if (Z_TYPE_P(retval) != IS_STRING) {
+					zend_error(E_ERROR, "Method %s::__toString() must return a string value", Z_OBJCE_P(readobj)->name);
+				}
+			} else {
+				MAKE_STD_ZVAL(retval);
+				ZVAL_STRINGL(retval, empty_string, 0, 0);
 			}
 			REPLACE_ZVAL_VALUE(&writeobj, retval, 0);
 			return SUCCESS;

Zend/zend_operators.c

@@ -445,7 +445,6 @@ ZEND_API void _convert_to_string(zval *op ZEND_FILE_LINE_DC)
 {
 	long lval;
 	double dval;
-	TSRMLS_FETCH();
 
 	switch (op->type) {
 		case IS_NULL:
@@ -465,6 +464,7 @@ ZEND_API void _convert_to_string(zval *op ZEND_FILE_LINE_DC)
 			break;
 		case IS_RESOURCE: {
 			long tmp = op->value.lval;
+			TSRMLS_FETCH();
 
 			zend_list_delete(op->value.lval);
 			op->value.str.val = (char *) emalloc(sizeof("Resource id #")-1 + MAX_LENGTH_OF_LONG);
@@ -478,6 +478,7 @@ ZEND_API void _convert_to_string(zval *op ZEND_FILE_LINE_DC)
 			op->value.str.len = zend_sprintf(op->value.str.val, "%ld", lval);  /* SAFE */
 			break;
 		case IS_DOUBLE: {
+			TSRMLS_FETCH();
 			dval = op->value.dval;
 			op->value.str.val = (char *) emalloc_rel(MAX_LENGTH_OF_DOUBLE + EG(precision) + 1);
 			op->value.str.len = zend_sprintf(op->value.str.val, "%.*G", (int) EG(precision), dval);  /* SAFE */
@@ -490,11 +491,11 @@ ZEND_API void _convert_to_string(zval *op ZEND_FILE_LINE_DC)
 			op->value.str.val = estrndup_rel("Array", sizeof("Array")-1);
 			op->value.str.len = sizeof("Array")-1;
 			break;
-		case IS_OBJECT:
+		case IS_OBJECT: {
+			TSRMLS_FETCH();
 			if (op->value.obj.handlers->cast_object) {
 				zval tmp;
-				TSRMLS_FETCH();
-				if (op->value.obj.handlers->cast_object(op, &tmp, IS_STRING, 1 TSRMLS_CC) == SUCCESS) {
+				if (op->value.obj.handlers->cast_object(op, &tmp, IS_STRING, 1 TSRMLS_CC) == SUCCESS && tmp.type == IS_STRING) {
 					zval_dtor(op);
 					*op = tmp;
 					break;
@@ -507,6 +508,7 @@ ZEND_API void _convert_to_string(zval *op ZEND_FILE_LINE_DC)
 			op->value.str.val = estrndup_rel("Object", sizeof("Object")-1);
 			op->value.str.len = sizeof("Object")-1;
 			break;
+		}
 		default:
 			zval_dtor(op);
 			ZVAL_BOOL(op, 0);