Merge "Update prebuilt Clang to r353983." into p9.0HEADp9.0-backupp9.0

1 files changed, 257 insertions, 0 deletions

diff --git a/clang-r353983/include/llvm/Support/CrashRecoveryContext.h b/clang-r353983/include/llvm/Support/CrashRecoveryContext.h
new file mode 100644
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+++ b/clang-r353983/include/llvm/Support/CrashRecoveryContext.h
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+//===--- CrashRecoveryContext.h - Crash Recovery ----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
+#define LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
+
+#include "llvm/ADT/STLExtras.h"
+
+namespace llvm {
+class CrashRecoveryContextCleanup;
+
+/// 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:
+///
+/// \code
+///    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 ...
+///    }
+/// \endcode
+///
+/// To assist recovery the class allows specifying set of actions that will be
+/// executed in any case, whether crash occurs or not. These actions may be used
+/// to reclaim resources in the case of crash.
+class CrashRecoveryContext {
+  void *Impl;
+  CrashRecoveryContextCleanup *head;
+
+public:
+  CrashRecoveryContext() : Impl(nullptr), head(nullptr) {}
+  ~CrashRecoveryContext();
+
+  /// Register cleanup handler, which is used when the recovery context is
+  /// finished.
+  /// The recovery context owns the handler.
+  void registerCleanup(CrashRecoveryContextCleanup *cleanup);
+
+  void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
+
+  /// Enable crash recovery.
+  static void Enable();
+
+  /// Disable crash recovery.
+  static void Disable();
+
+  /// Return the active context, if the code is currently executing in a
+  /// thread which is in a protected context.
+  static CrashRecoveryContext *GetCurrent();
+
+  /// Return true if the current thread is recovering from a crash.
+  static bool isRecoveringFromCrash();
+
+  /// Execute the provided 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.
+  bool RunSafely(function_ref<void()> Fn);
+  bool RunSafely(void (*Fn)(void*), void *UserData) {
+    return RunSafely([&]() { Fn(UserData); });
+  }
+
+  /// 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().
+  ///
+  /// On Darwin, if PRIO_DARWIN_BG is set on the calling thread, it will be
+  /// propagated to the new thread as well.
+  bool RunSafelyOnThread(function_ref<void()>, unsigned RequestedStackSize = 0);
+  bool RunSafelyOnThread(void (*Fn)(void*), void *UserData,
+                         unsigned RequestedStackSize = 0) {
+    return RunSafelyOnThread([&]() { Fn(UserData); }, RequestedStackSize);
+  }
+
+  /// Explicitly trigger a crash recovery in the current process, and
+  /// return failure from RunSafely(). This function does not return.
+  void HandleCrash();
+};
+
+/// Abstract base class of cleanup handlers.
+///
+/// Derived classes override method recoverResources, which makes actual work on
+/// resource recovery.
+///
+/// Cleanup handlers are stored in a double list, which is owned and managed by
+/// a crash recovery context.
+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;
+};
+
+/// Base class of cleanup handler that controls recovery of resources of the
+/// given type.
+///
+/// \tparam Derived Class that uses this class as a base.
+/// \tparam T Type of controlled resource.
+///
+/// This class serves as a base for its template parameter as implied by
+/// Curiously Recurring Template Pattern.
+///
+/// This class factors out creation of a cleanup handler. The latter requires
+/// knowledge of the current recovery context, which is provided by this class.
+template<typename Derived, typename T>
+class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
+protected:
+  T *resource;
+  CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T *resource)
+      : CrashRecoveryContextCleanup(context), resource(resource) {}
+
+public:
+  /// Creates cleanup handler.
+  /// \param x Pointer to the resource recovered by this handler.
+  /// \return New handler or null if the method was called outside a recovery
+  ///         context.
+  static Derived *create(T *x) {
+    if (x) {
+      if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
+        return new Derived(context, x);
+    }
+    return nullptr;
+  }
+};
+
+/// Cleanup handler that reclaims resource by calling destructor on it.
+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();
+  }
+};
+
+/// Cleanup handler that reclaims resource by calling 'delete' on it.
+template <typename T>
+class CrashRecoveryContextDeleteCleanup : public
+  CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
+public:
+  CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
+    : CrashRecoveryContextCleanupBase<
+        CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
+
+  void recoverResources() override { delete this->resource; }
+};
+
+/// Cleanup handler that reclaims resource by calling its method 'Release'.
+template <typename T>
+class CrashRecoveryContextReleaseRefCleanup : public
+  CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T> {
+public:
+  CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
+                                        T *resource)
+    : CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>,
+          T>(context, resource) {}
+
+  void recoverResources() override { this->resource->Release(); }
+};
+
+/// Helper class for managing resource cleanups.
+///
+/// \tparam T Type of resource been reclaimed.
+/// \tparam Cleanup Class that defines how the resource is reclaimed.
+///
+/// Clients create objects of this type in the code executed in a crash recovery
+/// context to ensure that the resource will be reclaimed even in the case of
+/// crash. For example:
+///
+/// \code
+///    void actual_work(void *) {
+///      ...
+///      std::unique_ptr<Resource> R(new Resource());
+///      CrashRecoveryContextCleanupRegistrar D(R.get());
+///      ...
+///    }
+///
+///    void foo() {
+///      CrashRecoveryContext CRC;
+///
+///      if (!CRC.RunSafely(actual_work, 0)) {
+///         ... a crash was detected, report error to user ...
+///      }
+/// \endcode
+///
+/// If the code of `actual_work` in the example above does not crash, the
+/// destructor of CrashRecoveryContextCleanupRegistrar removes cleanup code from
+/// the current CrashRecoveryContext and the resource is reclaimed by the
+/// destructor of std::unique_ptr. If crash happens, destructors are not called
+/// and the resource is reclaimed by cleanup object registered in the recovery
+/// context by the constructor of CrashRecoveryContextCleanupRegistrar.
+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 = nullptr;
+  }
+};
+} // end namespace llvm
+
+#endif // LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H