/*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-#ifndef FOLLY_EXCEPTIONWRAPPER_H
-#define FOLLY_EXCEPTIONWRAPPER_H
+#pragma once
-#include <cassert>
#include <exception>
#include <memory>
-#include <folly/String.h>
-#include <folly/detail/ExceptionWrapper.h>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include <folly/ExceptionString.h>
+#include <folly/FBString.h>
namespace folly {
* can test or extract a pointer to a specific exception type with very little
* overhead.
*
- * Example usage:
- *
+ * \par Example usage:
+ * \par
+ * \code
* exception_wrapper globalExceptionWrapper;
*
* // Thread1
*
* // Thread2: Exceptions are bad!
* void processResult() {
- * auto ep = globalExceptionWrapper.get();
- * if (!ep.with_exception<FacePlantException>([&](
- * FacePlantException& faceplant) {
- * LOG(ERROR) << "FACEPLANT";
- * })) {
- * ep.with_exception<FailWhaleException>([&](
- * FailWhaleException& failwhale) {
+ * globalExceptionWrapper.with_exception(
+ * [&](FacePlantException& faceplant) {
+ * LOG(ERROR) << "FACEPLANT";
+ * }) ||
+ * globalExceptionWrapper.with_exception(
+ * [&](FailWhaleException& failwhale) {
* LOG(ERROR) << "FAILWHALE!";
- * });
- * }
+ * }) ||
+ * LOG(FATAL) << "Unrecognized exception";
* }
+ * \endcode
*
*/
class exception_wrapper {
- protected:
+ private:
template <typename Ex>
struct optimize;
::type>
/* implicit */ exception_wrapper(Ex&& exn) {
typedef typename std::decay<Ex>::type DEx;
- item_ = std::make_shared<DEx>(std::forward<Ex>(exn));
- throwfn_ = folly::detail::Thrower<DEx>::doThrow;
+ assign_sptr(std::make_shared<DEx>(std::forward<Ex>(exn)));
}
// The following two constructors are meant to emulate the behavior of
assign_eptr(eptr);
}
- void throwException() const {
- if (throwfn_) {
- throwfn_(item_.get());
- } else if (eptr_) {
- std::rethrow_exception(eptr_);
- }
- }
+ // If the exception_wrapper does not contain an exception, std::terminate()
+ // is invoked to assure the [[noreturn]] behaviour.
+ [[noreturn]] void throwException() const;
explicit operator bool() const {
return item_ || eptr_;
std::exception* getCopied() { return item_.get(); }
const std::exception* getCopied() const { return item_.get(); }
- fbstring what() const {
- if (item_) {
- return exceptionStr(*item_);
- } else if (eptr_) {
- return estr_;
- } else {
- return fbstring();
- }
- }
-
- fbstring class_name() const {
- if (item_) {
- auto& i = *item_;
- return demangle(typeid(i));
- } else if (eptr_) {
- return ename_;
- } else {
- return fbstring();
- }
- }
+ fbstring what() const;
+ fbstring class_name() const;
template <class Ex>
bool is_compatible_with() const {
- if (item_) {
- return dynamic_cast<const Ex*>(item_.get());
- } else if (eptr_) {
- try {
- std::rethrow_exception(eptr_);
- } catch (typename std::decay<Ex>::type&) {
- return true;
- } catch (...) {
- // fall through
- }
- }
- return false;
+ return with_exception<Ex>([](const Ex&) {});
}
template <class F>
template <class F>
bool with_exception(F&& f) const {
using arg_type = typename functor_traits<F>::arg_type_decayed;
- return with_exception<const arg_type>(std::forward<F>(f));
+ return with_exception<arg_type>(std::forward<F>(f));
}
// If this exception wrapper wraps an exception of type Ex, with_exception
// will call f with the wrapped exception as an argument and return true, and
// will otherwise return false.
template <class Ex, class F>
- typename std::enable_if<
- std::is_base_of<std::exception, typename std::decay<Ex>::type>::value,
- bool>::type
- with_exception(F f) {
+ bool with_exception(F f) {
return with_exception1<typename std::decay<Ex>::type>(f, this);
}
// Const overload
template <class Ex, class F>
- typename std::enable_if<
- std::is_base_of<std::exception, typename std::decay<Ex>::type>::value,
- bool>::type
- with_exception(F f) const {
- return with_exception1<const typename std::decay<Ex>::type>(f, this);
- }
-
- // Overload for non-exceptions. Always rethrows.
- template <class Ex, class F>
- typename std::enable_if<
- !std::is_base_of<std::exception, typename std::decay<Ex>::type>::value,
- bool>::type
- with_exception(F f) const {
- try {
- throwException();
- } catch (typename std::decay<Ex>::type& e) {
- f(e);
- return true;
- } catch (...) {
- // fall through
- }
- return false;
+ bool with_exception(F f) const {
+ return with_exception1<typename std::decay<Ex>::type>(f, this);
}
std::exception_ptr getExceptionPtr() const {
}
try {
- throwException();
+ if (*this) {
+ throwException();
+ }
} catch (...) {
return std::current_exception();
}
return std::exception_ptr();
}
-protected:
+ private:
template <typename Ex>
struct optimize {
static const bool value =
!std::is_abstract<Ex>::value;
};
+ template <typename Ex>
+ void assign_sptr(std::shared_ptr<Ex> sptr) {
+ this->item_ = std::move(sptr);
+ this->throwfn_ = Thrower<Ex>::doThrow;
+ }
+
template <typename Ex>
void assign_eptr(std::exception_ptr eptr, Ex& e) {
this->eptr_ = eptr;
// store a copy of the concrete type, and a helper function so we
// can rethrow it.
std::shared_ptr<std::exception> item_;
- void (*throwfn_)(std::exception*){nullptr};
+ void (*throwfn_)(std::exception&){nullptr};
// Fallback case: store the library wrapper, which is less efficient
// but gets the job done. Also store exceptionPtr() the name of the
// exception type, so we can at least get those back out without
template <class T, class... Args>
friend exception_wrapper make_exception_wrapper(Args&&... args);
-private:
+ private:
template <typename F>
struct functor_traits {
template <typename T>
using arg_type_decayed = typename std::decay<arg_type>::type;
};
+ template <class T>
+ class Thrower {
+ public:
+ static void doThrow(std::exception& obj) {
+ throw static_cast<T&>(obj);
+ }
+ };
+
+ template <typename T>
+ using is_exception_ = std::is_base_of<std::exception, T>;
+
+ template <bool V, typename T, typename F>
+ using conditional_t_ = typename std::conditional<V, T, F>::type;
+
+ template <typename T, typename F>
+ static typename std::enable_if<is_exception_<T>::value, T*>::type
+ try_dynamic_cast_exception(F* from) {
+ return dynamic_cast<T*>(from);
+ }
+ template <typename T, typename F>
+ static typename std::enable_if<!is_exception_<T>::value, T*>::type
+ try_dynamic_cast_exception(F*) {
+ return nullptr;
+ }
+
// What makes this useful is that T can be exception_wrapper* or
// const exception_wrapper*, and the compiler will use the
// instantiation which works with F.
template <class Ex, class F, class T>
static bool with_exception1(F f, T* that) {
- if (that->item_) {
- if (auto ex = dynamic_cast<Ex*>(that->item_.get())) {
+ using CEx = conditional_t_<std::is_const<T>::value, const Ex, Ex>;
+ if (is_exception_<Ex>::value && that->item_) {
+ if (auto ex = try_dynamic_cast_exception<CEx>(that->item_.get())) {
f(*ex);
return true;
}
} else if (that->eptr_) {
try {
std::rethrow_exception(that->eptr_);
- } catch (Ex& e) {
+ } catch (CEx& e) {
f(e);
return true;
} catch (...) {
template <class T, class... Args>
exception_wrapper make_exception_wrapper(Args&&... args) {
exception_wrapper ew;
- ew.item_ = std::make_shared<T>(std::forward<Args>(args)...);
- ew.throwfn_ = folly::detail::Thrower<T>::doThrow;
+ ew.assign_sptr(std::make_shared<T>(std::forward<Args>(args)...));
return ew;
}
-// For consistency with exceptionStr() functions in String.h
-inline fbstring exceptionStr(const exception_wrapper& ew) {
- return ew.what();
-}
+// For consistency with exceptionStr() functions in ExceptionString.h
+fbstring exceptionStr(const exception_wrapper& ew);
/*
* try_and_catch is a simple replacement for try {} catch(){} that allows you to
* });
*/
-template <typename... Exceptions>
-class try_and_catch;
+namespace try_and_catch_detail {
-template <typename LastException, typename... Exceptions>
-class try_and_catch<LastException, Exceptions...> :
- public try_and_catch<Exceptions...> {
- public:
- template <typename F>
- explicit try_and_catch(F&& fn) : Base() {
- call_fn(fn);
- }
+template <bool V, typename T = void>
+using enable_if_t_ = typename std::enable_if<V, T>::type;
- protected:
- typedef try_and_catch<Exceptions...> Base;
+template <typename... Args>
+using is_wrap_ctor = std::is_constructible<exception_wrapper, Args...>;
- try_and_catch() : Base() {}
+template <typename Ex>
+inline enable_if_t_<!is_wrap_ctor<Ex&>::value, exception_wrapper> make(Ex& ex) {
+ return exception_wrapper(std::current_exception(), ex);
+}
- template <typename Ex>
- typename std::enable_if<!exception_wrapper::optimize<Ex>::value>::type
- assign_exception(Ex& e, std::exception_ptr eptr) {
- exception_wrapper::assign_eptr(eptr, e);
- }
+template <typename Ex>
+inline enable_if_t_<is_wrap_ctor<Ex&>::value, exception_wrapper> make(Ex& ex) {
+ return typeid(Ex&) == typeid(ex)
+ ? exception_wrapper(ex)
+ : exception_wrapper(std::current_exception(), ex);
+}
- template <typename Ex>
- typename std::enable_if<exception_wrapper::optimize<Ex>::value>::type
- assign_exception(Ex& e, std::exception_ptr /*eptr*/) {
- this->item_ = std::make_shared<Ex>(e);
- this->throwfn_ = folly::detail::Thrower<Ex>::doThrow;
- }
+template <typename F>
+inline exception_wrapper impl(F&& f) {
+ return (f(), exception_wrapper());
+}
- template <typename F>
- void call_fn(F&& fn) {
- try {
- Base::call_fn(std::move(fn));
- } catch (LastException& e) {
- if (typeid(e) == typeid(LastException&)) {
- assign_exception(e, std::current_exception());
- } else {
- exception_wrapper::assign_eptr(std::current_exception(), e);
- }
- }
+template <typename F, typename Ex, typename... Exs>
+inline exception_wrapper impl(F&& f) {
+ try {
+ return impl<F, Exs...>(std::forward<F>(f));
+ } catch (Ex& ex) {
+ return make(ex);
}
-};
-
-template<>
-class try_and_catch<> : public exception_wrapper {
- public:
- try_and_catch() = default;
+}
+} // try_and_catch_detail
- protected:
- template <typename F>
- void call_fn(F&& fn) {
- fn();
- }
-};
+template <typename... Exceptions, typename F>
+exception_wrapper try_and_catch(F&& fn) {
+ return try_and_catch_detail::impl<F, Exceptions...>(std::forward<F>(fn));
}
-#endif
+} // folly
projects / folly.git / blobdiff