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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <cstdarg>
#include <memory>
#include "src/base/compiler-specific.h"
#include "src/base/macros.h"
#include "src/base/platform/platform.h"
#include "src/common/globals.h"
namespace v8 {
namespace internal {
class Isolate;
template <typename T>
class Handle;
namespace wasm {
class V8_EXPORT_PRIVATE WasmError {
WasmError() = default;
WasmError(uint32_t offset, std::string message)
: offset_(offset), message_(std::move(message)) {
// The error message must not be empty, otherwise {empty()} would be true.
WasmError(uint32_t offset, const char* format, ...) : offset_(offset) {
va_list args;
va_start(args, format);
message_ = FormatError(format, args);
// The error message must not be empty, otherwise {empty()} would be true.
bool empty() const { return message_.empty(); }
bool has_error() const { return !message_.empty(); }
uint32_t offset() const { return offset_; }
const std::string& message() const& { return message_; }
std::string&& message() && { return std::move(message_); }
static std::string FormatError(const char* format, va_list args);
uint32_t offset_ = 0;
std::string message_;
// Either a result of type T, or a WasmError.
template <typename T>
class Result {
Result() = default;
Result(const Result&) = delete;
Result& operator=(const Result&) = delete;
template <typename S>
explicit Result(S&& value) : value_(std::forward<S>(value)) {}
template <typename S>
Result(Result<S>&& other) V8_NOEXCEPT : value_(std::move(other.value_)),
error_(std::move(other.error_)) {}
explicit Result(WasmError error) : error_(std::move(error)) {}
template <typename S>
Result& operator=(Result<S>&& other) V8_NOEXCEPT {
value_ = std::move(other.value_);
error_ = std::move(other.error_);
return *this;
bool ok() const { return error_.empty(); }
bool failed() const { return error_.has_error(); }
const WasmError& error() const& { return error_; }
WasmError&& error() && { return std::move(error_); }
// Accessor for the value. Returns const reference if {this} is l-value or
// const, and returns r-value reference if {this} is r-value. This allows to
// extract non-copyable values like {std::unique_ptr} by using
// {std::move(result).value()}.
const T& value() const & {
return value_;
T&& value() && {
return std::move(value_);
template <typename S>
friend class Result;
T value_ = T{};
WasmError error_;
// A helper for generating error messages that bubble up to JS exceptions.
class V8_EXPORT_PRIVATE ErrorThrower {
ErrorThrower(Isolate* isolate, const char* context)
: isolate_(isolate), context_(context) {}
// Explicitly allow move-construction. Disallow copy.
ErrorThrower(ErrorThrower&& other) V8_NOEXCEPT;
ErrorThrower(const ErrorThrower&) = delete;
ErrorThrower& operator=(const ErrorThrower&) = delete;
PRINTF_FORMAT(2, 3) void TypeError(const char* fmt, ...);
PRINTF_FORMAT(2, 3) void RangeError(const char* fmt, ...);
PRINTF_FORMAT(2, 3) void CompileError(const char* fmt, ...);
PRINTF_FORMAT(2, 3) void LinkError(const char* fmt, ...);
PRINTF_FORMAT(2, 3) void RuntimeError(const char* fmt, ...);
void CompileFailed(const WasmError& error) {
CompileError("%s @+%u", error.message().c_str(), error.offset());
// Create and return exception object.
V8_WARN_UNUSED_RESULT Handle<Object> Reify();
// Reset any error which was set on this thrower.
void Reset();
bool error() const { return error_type_ != kNone; }
bool wasm_error() { return error_type_ >= kFirstWasmError; }
const char* error_msg() { return error_msg_.c_str(); }
Isolate* isolate() const { return isolate_; }
enum ErrorType {
// General errors.
// Wasm errors.
// Marker.
kFirstWasmError = kCompileError
void Format(ErrorType error_type_, const char* fmt, va_list);
Isolate* isolate_;
const char* context_;
ErrorType error_type_ = kNone;
std::string error_msg_;
// ErrorThrower should always be stack-allocated, since it constitutes a scope
// (things happen in the destructor).
// Like an ErrorThrower, but turns all pending exceptions into scheduled
// exceptions when going out of scope. Use this in API methods.
// Note that pending exceptions are not necessarily created by the ErrorThrower,
// but e.g. by the wasm start function. There might also be a scheduled
// exception, created by another API call (e.g. v8::Object::Get). But there
// should never be both pending and scheduled exceptions.
class V8_EXPORT_PRIVATE ScheduledErrorThrower : public ErrorThrower {
ScheduledErrorThrower(i::Isolate* isolate, const char* context)
: ErrorThrower(isolate, context) {}
// Use {nullptr_t} as data value to indicate that this only stores the error,
// but no result value (the only valid value is {nullptr}).
// [Storing {void} would require template specialization.]
using VoidResult = Result<std::nullptr_t>;
} // namespace wasm
} // namespace internal
} // namespace v8
#endif // V8_WASM_WASM_RESULT_H_