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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef vm_ErrorObject_h_
#define vm_ErrorObject_h_
#include "mozilla/Assertions.h"
#include "mozilla/Maybe.h"
#include <iterator>
#include <stdint.h>
#include "jspubtd.h"
#include "NamespaceImports.h"
#include "js/Class.h"
#include "js/ColumnNumber.h" // JS::ColumnNumberOneOrigin
#include "js/ErrorReport.h"
#include "js/RootingAPI.h"
#include "js/TypeDecls.h"
#include "js/UniquePtr.h"
#include "js/Value.h"
#include "vm/JSObject.h"
#include "vm/NativeObject.h"
namespace js {
class ErrorObject : public NativeObject {
static JSObject* createProto(JSContext* cx, JSProtoKey key);
static JSObject* createConstructor(JSContext* cx, JSProtoKey key);
static bool init(JSContext* cx, Handle<ErrorObject*> obj, JSExnType type,
UniquePtr<JSErrorReport> errorReport, HandleString fileName,
HandleObject stack, uint32_t sourceId, uint32_t lineNumber,
JS::ColumnNumberOneOrigin columnNumber, HandleString message,
Handle<mozilla::Maybe<JS::Value>> cause);
static const ClassSpec classSpecs[JSEXN_ERROR_LIMIT];
static const JSClass protoClasses[JSEXN_ERROR_LIMIT];
static const uint32_t STACK_SLOT = 0;
static const uint32_t ERROR_REPORT_SLOT = STACK_SLOT + 1;
static const uint32_t FILENAME_SLOT = ERROR_REPORT_SLOT + 1;
static const uint32_t LINENUMBER_SLOT = FILENAME_SLOT + 1;
static const uint32_t COLUMNNUMBER_SLOT = LINENUMBER_SLOT + 1;
static const uint32_t MESSAGE_SLOT = COLUMNNUMBER_SLOT + 1;
static const uint32_t CAUSE_SLOT = MESSAGE_SLOT + 1;
static const uint32_t SOURCEID_SLOT = CAUSE_SLOT + 1;
static const uint32_t RESERVED_SLOTS = SOURCEID_SLOT + 1;
// This slot is only used for errors that could be Wasm traps.
static const uint32_t WASM_TRAP_SLOT = SOURCEID_SLOT + 1;
static const JSClass classes[JSEXN_ERROR_LIMIT];
static const JSClass* classForType(JSExnType type) {
return &classes[type];
static bool isErrorClass(const JSClass* clasp) {
return &classes[0] <= clasp && clasp < &classes[0] + std::size(classes);
// Create an error of the given type corresponding to the provided location
// info. If |message| is non-null, then the error will have a .message
// property with that value; otherwise the error will have no .message
// property.
static ErrorObject* create(JSContext* cx, JSExnType type, HandleObject stack,
HandleString fileName, uint32_t sourceId,
uint32_t lineNumber,
JS::ColumnNumberOneOrigin columnNumber,
UniquePtr<JSErrorReport> report,
HandleString message,
Handle<mozilla::Maybe<JS::Value>> cause,
HandleObject proto = nullptr);
* Assign the initial error shape to the empty object. (This shape does
* *not* include .message, which must be added separately if needed; see
* ErrorObject::init.)
static SharedShape* assignInitialShape(JSContext* cx,
Handle<ErrorObject*> obj);
JSExnType type() const {
return static_cast<JSExnType>(getClass() - &classes[0]);
JSErrorReport* getErrorReport() const {
const Value& slot = getReservedSlot(ERROR_REPORT_SLOT);
if (slot.isUndefined()) {
return nullptr;
return static_cast<JSErrorReport*>(slot.toPrivate());
JSErrorReport* getOrCreateErrorReport(JSContext* cx);
inline JSString* fileName(JSContext* cx) const;
inline uint32_t sourceId() const;
// Line number (1-origin).
inline uint32_t lineNumber() const;
// Column number in UTF-16 code units.
inline JS::ColumnNumberOneOrigin columnNumber() const;
// Returns nullptr or a (possibly wrapped) SavedFrame object.
inline JSObject* stack() const;
JSString* getMessage() const {
Value val = getReservedSlot(MESSAGE_SLOT);
return val.isString() ? val.toString() : nullptr;
* Return Nothing if the error was created without an initial cause or if the
* initial cause data property has been redefined to an accessor property.
mozilla::Maybe<Value> getCause() const {
const auto& value = getReservedSlot(CAUSE_SLOT);
if (value.isMagic(JS_ERROR_WITHOUT_CAUSE) || value.isPrivateGCThing()) {
return mozilla::Nothing();
return mozilla::Some(value);
void setStackSlot(const Value& stack) {
setReservedSlot(STACK_SLOT, stack);
void setCauseSlot(const Value& cause) {
setReservedSlot(CAUSE_SLOT, cause);
// Getter and setter for the Error.prototype.stack accessor.
static bool getStack(JSContext* cx, unsigned argc, Value* vp);
static bool getStack_impl(JSContext* cx, const CallArgs& args);
static bool setStack(JSContext* cx, unsigned argc, Value* vp);
static bool setStack_impl(JSContext* cx, const CallArgs& args);
// Used to distinguish errors created from Wasm traps.
bool mightBeWasmTrap() const {
bool fromWasmTrap() const {
if (!mightBeWasmTrap()) {
return false;
} else {
return getReservedSlot(WASM_TRAP_SLOT).toBoolean();
void setFromWasmTrap();
JSString* ErrorToSource(JSContext* cx, HandleObject obj);
} // namespace js
template <>
inline bool JSObject::is<js::ErrorObject>() const {
return js::ErrorObject::isErrorClass(getClass());
#endif // vm_ErrorObject_h_