241 lines
7.1 KiB
C++
241 lines
7.1 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <exception>
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#include <type_traits>
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#include <utility>
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#include <folly/CPortability.h>
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#include <folly/CppAttributes.h>
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#include <folly/Portability.h>
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namespace folly {
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/// throw_exception
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///
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/// Throw an exception if exceptions are enabled, or terminate if compiled with
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/// -fno-exceptions.
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template <typename Ex>
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[[noreturn]] FOLLY_NOINLINE FOLLY_COLD void throw_exception(Ex&& ex) {
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#if FOLLY_HAS_EXCEPTIONS
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throw static_cast<Ex&&>(ex);
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#else
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(void)ex;
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std::terminate();
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#endif
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}
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/// terminate_with
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///
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/// Terminates as if by forwarding to throw_exception but in a noexcept context.
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template <typename Ex>
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[[noreturn]] FOLLY_NOINLINE FOLLY_COLD void terminate_with(Ex&& ex) noexcept {
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throw_exception(static_cast<Ex&&>(ex));
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}
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// clang-format off
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namespace detail {
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template <typename T>
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FOLLY_ERASE T&& to_exception_arg_(T&& t) {
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return static_cast<T&&>(t);
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}
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template <std::size_t N>
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FOLLY_ERASE char const* to_exception_arg_(
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char const (&array)[N]) {
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return static_cast<char const*>(array);
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}
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template <typename Ex, typename... Args>
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[[noreturn]] FOLLY_NOINLINE FOLLY_COLD void throw_exception_(Args&&... args) {
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throw_exception(Ex(static_cast<Args&&>(args)...));
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}
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template <typename Ex, typename... Args>
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[[noreturn]] FOLLY_NOINLINE FOLLY_COLD void terminate_with_(
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Args&&... args) noexcept {
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throw_exception(Ex(static_cast<Args&&>(args)...));
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}
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} // namespace detail
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// clang-format on
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/// throw_exception
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///
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/// Construct and throw an exception if exceptions are enabled, or terminate if
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/// compiled with -fno-exceptions.
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///
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/// Converts any arguments of type `char const[N]` to `char const*`.
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template <typename Ex, typename... Args>
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[[noreturn]] FOLLY_ERASE void throw_exception(Args&&... args) {
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detail::throw_exception_<Ex>(
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detail::to_exception_arg_(static_cast<Args&&>(args))...);
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}
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/// terminate_with
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///
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/// Terminates as if by forwarding to throw_exception but in a noexcept context.
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// clang-format off
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template <typename Ex, typename... Args>
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[[noreturn]] FOLLY_ERASE void
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terminate_with(Args&&... args) noexcept {
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detail::terminate_with_<Ex>(
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detail::to_exception_arg_(static_cast<Args&&>(args))...);
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}
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// clang-format on
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/// invoke_cold
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///
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/// Invoke the provided function with the provided arguments.
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///
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/// Usage note:
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/// Passing extra values as arguments rather than capturing them allows smaller
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/// inlined native at the call-site.
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///
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/// Example:
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///
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/// if (i < 0) {
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/// invoke_cold(
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/// [](int j) {
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/// std::string ret = doStepA();
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/// doStepB(ret);
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/// doStepC(ret);
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/// },
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/// i);
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/// }
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template <typename F, typename... A>
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FOLLY_NOINLINE FOLLY_COLD auto invoke_cold(F&& f, A&&... a)
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-> decltype(static_cast<F&&>(f)(static_cast<A&&>(a)...)) {
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return static_cast<F&&>(f)(static_cast<A&&>(a)...);
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}
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/// invoke_noreturn_cold
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///
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/// Invoke the provided function with the provided arguments. If the invocation
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/// returns, terminate.
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///
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/// May be used with throw_exception in cases where construction of the object
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/// to be thrown requires more than just invoking its constructor with a given
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/// sequence of arguments passed by reference - for example, if a string message
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/// must be computed before being passed to the constructor of the object to be
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/// thrown.
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///
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/// Usage note:
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/// Passing extra values as arguments rather than capturing them allows smaller
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/// inlined native code at the call-site.
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///
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/// Example:
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///
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/// if (i < 0) {
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/// invoke_noreturn_cold(
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/// [](int j) {
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/// throw_exceptions(runtime_error(to<string>("invalid: ", j)));
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/// },
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/// i);
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/// }
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template <typename F, typename... A>
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[[noreturn]] FOLLY_NOINLINE FOLLY_COLD void invoke_noreturn_cold(
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F&& f,
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A&&... a) {
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static_cast<F&&>(f)(static_cast<A&&>(a)...);
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std::terminate();
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}
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/// catch_exception
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///
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/// Invokes t; if exceptions are enabled (if not compiled with -fno-exceptions),
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/// catches a thrown exception e of type E and invokes c, forwarding e and any
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/// trailing arguments.
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///
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/// Usage note:
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/// As a general rule, pass Ex const& rather than unqualified Ex as the explicit
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/// template argument E. The catch statement catches E without qualifiers so
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/// if E is Ex then that translates to catch (Ex), but if E is Ex const& then
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/// that translates to catch (Ex const&).
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///
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/// Usage note:
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/// Passing extra values as arguments rather than capturing them allows smaller
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/// inlined native code at the call-site.
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///
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/// Example:
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///
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/// int input = // ...
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/// int def = 45;
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/// auto result = catch_exception<std::runtime_error const&>(
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/// [=] {
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/// if (input < 0) throw std::runtime_error("foo");
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/// return input;
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/// },
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/// [](auto&& e, int num) { return num; },
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/// def);
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/// assert(result == input < 0 ? def : input);
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template <typename E, typename Try, typename Catch, typename... CatchA>
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FOLLY_ERASE_TRYCATCH auto catch_exception(Try&& t, Catch&& c, CatchA&&... a) ->
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typename std::common_type<
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decltype(static_cast<Try&&>(t)()),
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decltype(static_cast<Catch&&>(
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c)(std::declval<E>(), static_cast<CatchA&&>(a)...))>::type {
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#if FOLLY_HAS_EXCEPTIONS
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try {
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return static_cast<Try&&>(t)();
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} catch (E e) {
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return invoke_cold(static_cast<Catch&&>(c), e, static_cast<CatchA&&>(a)...);
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}
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#else
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[](auto&&...) {}(c, a...); // ignore
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return static_cast<Try&&>(t)();
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#endif
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}
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/// catch_exception
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///
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/// Invokes t; if exceptions are enabled (if not compiled with -fno-exceptions),
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/// catches a thrown exception of any type and invokes c, forwarding any
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/// trailing arguments.
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//
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/// Usage note:
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/// Passing extra values as arguments rather than capturing them allows smaller
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/// inlined native code at the call-site.
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///
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/// Example:
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///
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/// int input = // ...
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/// int def = 45;
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/// auto result = catch_exception(
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/// [=] {
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/// if (input < 0) throw 11;
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/// return input;
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/// },
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/// [](int num) { return num; },
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/// def);
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/// assert(result == input < 0 ? def : input);
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template <typename Try, typename Catch, typename... CatchA>
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FOLLY_ERASE_TRYCATCH auto catch_exception(Try&& t, Catch&& c, CatchA&&... a) ->
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typename std::common_type<
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decltype(static_cast<Try&&>(t)()),
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decltype(static_cast<Catch&&>(c)(static_cast<CatchA&&>(a)...))>::type {
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#if FOLLY_HAS_EXCEPTIONS
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try {
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return static_cast<Try&&>(t)();
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} catch (...) {
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return invoke_cold(static_cast<Catch&&>(c), static_cast<CatchA&&>(a)...);
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}
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#else
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[](auto&&...) {}(c, a...); // ignore
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return static_cast<Try&&>(t)();
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#endif
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}
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} // namespace folly
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