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04d873a27a
Summary: I frequently find myself forgetting how to make the compiler see that non-moved-from EDEN_BUG's destructor is noreturn, so add a simple throwException function to it. Reviewed By: simpkins Differential Revision: D7834182 fbshipit-source-id: f279b9ca24f90efb4ad3ac318606dbd2dd002665
133 lines
3.8 KiB
C++
133 lines
3.8 KiB
C++
/*
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* Copyright (c) 2016-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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*/
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#pragma once
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#include <folly/Conv.h>
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#include <folly/lang/ColdClass.h>
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#include <atomic>
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#include <string>
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/**
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* EDEN_BUG() should be used to log logic errors that should not happen unless
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* there is a bug in the code.
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*
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* In debug builds this macro will cause the program to crash.
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* However, in production builds crashing the program is fairly harsh, as this
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* will destroy the client mount points, causing problems for any open programs
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* or shells the user had that were using eden mounts. Therefore in production
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* builds EDEN_BUG() just logs the error and then throws an exception that can
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* be handled by the calling code.
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*
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* Use XLOG(FATAL) if you want to crash the program even in production builds.
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*
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* Example uses:
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*
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* Log a message and throw an exception:
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*
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* EDEN_BUG() << "bad stuff happened";
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*
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* Log a message, but convert the exception to a folly::exception_wrapper()
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* and return it as a folly::Future:
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*
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* auto bug = EDEN_BUG() << "bad stuff happened";
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* return folly::makeFuture<InodePtr>(bug.toException());
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*
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* You should only store the return value of EDEN_BUG() in order to call
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* toException() on it. Storing the return value prevents it from immediately
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* throwing in the EDEN_BUG() statement.
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*/
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#define EDEN_BUG() ::facebook::eden::EdenBug(__FILE__, __LINE__)
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namespace folly {
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class exception_wrapper;
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}
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namespace facebook {
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namespace eden {
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/**
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* A helper class returned by the EDEN_BUG() macro.
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*
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* toException() can be called to convert it to a folly::exception_wrapper
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* If toException() has not been called, it will throw an exception when it is
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* destroyed.
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*
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* In debug builds EdenBug causes the program to abort rather than throwing or
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* returning an exception.
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*/
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class EdenBug : public folly::ColdClass {
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public:
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EdenBug(const char* file, int lineNumber);
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EdenBug(EdenBug&& other) noexcept;
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EdenBug& operator=(EdenBug&& other) = delete;
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~EdenBug() noexcept(false);
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/**
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* Append to the bug message.
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*/
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template <typename T>
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EdenBug&& operator<<(T&& t) && {
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using folly::toAppend;
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toAppend(std::forward<T>(t), &message_);
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return std::move(*this);
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}
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/**
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* Convert this EdenBug object to a folly::exception_wrapper
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*
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* If toException() is never called on an EdenBug object, it will throw on
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* destruction.
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*/
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folly::exception_wrapper toException();
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/**
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* A wrapper for toException().throw_exception(). A typical use of EDEN_BUG()
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* where the bug is captured is actually noreturn, but the compiler can't see
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* that because moved-from EdenBug doesn't throw.
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*
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* To avoid compiler warnings, write:
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* auto bug = EDEN_BUG() << "...";
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* bug.throwException();
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*/
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[[noreturn]] void throwException();
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/**
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* Prevent EDEN_BUG() from crashing the program, even in debug builds.
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*
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* This is intended to allow unit tests to disable crashing.
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* This generally shouldn't ever be called from normal production code.
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*/
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static void acquireDisableCrashLease();
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static void releaseDisableCrashLease();
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private:
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void logError();
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const char* file_;
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int lineNumber_;
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bool throwOnDestruction_{true};
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std::string message_;
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};
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/**
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* EdenBugDisabler temporarily disables crashing on EDEN_BUG as long as it
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* exists.
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*/
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class EdenBugDisabler {
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public:
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EdenBugDisabler();
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~EdenBugDisabler();
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EdenBugDisabler(const EdenBugDisabler&) = delete;
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EdenBugDisabler operator=(const EdenBugDisabler&) = delete;
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};
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} // namespace eden
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} // namespace facebook
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