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//===--- CrashRecoveryContext.h - Crash Recovery ----------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
#define LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
#include <string>
namespace llvm {
class StringRef;
class CrashRecoveryContextCleanup;
/// \brief Crash recovery helper object.
///
/// This class implements support for running operations in a safe context so
/// that crashes (memory errors, stack overflow, assertion violations) can be
/// detected and control restored to the crashing thread. Crash detection is
/// purely "best effort", the exact set of failures which can be recovered from
/// is platform dependent.
///
/// Clients make use of this code by first calling
/// CrashRecoveryContext::Enable(), and then executing unsafe operations via a
/// CrashRecoveryContext object. For example:
///
/// void actual_work(void *);
///
/// void foo() {
/// CrashRecoveryContext CRC;
///
/// if (!CRC.RunSafely(actual_work, 0)) {
/// ... a crash was detected, report error to user ...
/// }
///
/// ... no crash was detected ...
/// }
///
/// Crash recovery contexts may not be nested.
class CrashRecoveryContext {
void *Impl;
CrashRecoveryContextCleanup *head;
public:
CrashRecoveryContext() : Impl(0), head(0) {}
~CrashRecoveryContext();
void registerCleanup(CrashRecoveryContextCleanup *cleanup);
void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
/// \brief Enable crash recovery.
static void Enable();
/// \brief Disable crash recovery.
static void Disable();
/// \brief Return the active context, if the code is currently executing in a
/// thread which is in a protected context.
static CrashRecoveryContext *GetCurrent();
/// \brief Return true if the current thread is recovering from a
/// crash.
static bool isRecoveringFromCrash();
/// \brief Execute the provide callback function (with the given arguments) in
/// a protected context.
///
/// \return True if the function completed successfully, and false if the
/// function crashed (or HandleCrash was called explicitly). Clients should
/// make as little assumptions as possible about the program state when
/// RunSafely has returned false. Clients can use getBacktrace() to retrieve
/// the backtrace of the crash on failures.
bool RunSafely(void (*Fn)(void*), void *UserData);
/// \brief Execute the provide callback function (with the given arguments) in
/// a protected context which is run in another thread (optionally with a
/// requested stack size).
///
/// See RunSafely() and llvm_execute_on_thread().
bool RunSafelyOnThread(void (*Fn)(void*), void *UserData,
unsigned RequestedStackSize = 0);
/// \brief Explicitly trigger a crash recovery in the current process, and
/// return failure from RunSafely(). This function does not return.
void HandleCrash();
/// \brief Return a string containing the backtrace where the crash was
/// detected; or empty if the backtrace wasn't recovered.
///
/// This function is only valid when a crash has been detected (i.e.,
/// RunSafely() has returned false.
const std::string &getBacktrace() const;
};
class CrashRecoveryContextCleanup {
protected:
CrashRecoveryContext *context;
CrashRecoveryContextCleanup(CrashRecoveryContext *context)
: context(context), cleanupFired(false) {}
public:
bool cleanupFired;
virtual ~CrashRecoveryContextCleanup();
virtual void recoverResources() = 0;
CrashRecoveryContext *getContext() const {
return context;
}
private:
friend class CrashRecoveryContext;
CrashRecoveryContextCleanup *prev, *next;
};
template<typename DERIVED, typename T>
class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
protected:
T *resource;
CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T* resource)
: CrashRecoveryContextCleanup(context), resource(resource) {}
public:
static DERIVED *create(T *x) {
if (x) {
if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
return new DERIVED(context, x);
}
return 0;
}
};
template <typename T>
class CrashRecoveryContextDestructorCleanup : public
CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
public:
CrashRecoveryContextDestructorCleanup(CrashRecoveryContext *context,
T *resource)
: CrashRecoveryContextCleanupBase<
CrashRecoveryContextDestructorCleanup<T>, T>(context, resource) {}
virtual void recoverResources() {
this->resource->~T();
}
};
template <typename T>
class CrashRecoveryContextDeleteCleanup : public
CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
public:
CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
: CrashRecoveryContextCleanupBase<
CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
virtual void recoverResources() {
delete this->resource;
}
};
template <typename T>
class CrashRecoveryContextReleaseRefCleanup : public
CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T>
{
public:
CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
T *resource)
: CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>,
T>(context, resource) {}
virtual void recoverResources() {
this->resource->Release();
}
};
template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
class CrashRecoveryContextCleanupRegistrar {
CrashRecoveryContextCleanup *cleanup;
public:
CrashRecoveryContextCleanupRegistrar(T *x)
: cleanup(Cleanup::create(x)) {
if (cleanup)
cleanup->getContext()->registerCleanup(cleanup);
}
~CrashRecoveryContextCleanupRegistrar() {
unregister();
}
void unregister() {
if (cleanup && !cleanup->cleanupFired)
cleanup->getContext()->unregisterCleanup(cleanup);
cleanup = 0;
}
};
}
#endif
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