Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 217 insertions, 0 deletions

diff --git a/mozglue/baseprofiler/public/FailureLatch.h b/mozglue/baseprofiler/public/FailureLatch.h
new file mode 100644
index 0000000000..10205e009b
--- /dev/null
+++ b/mozglue/baseprofiler/public/FailureLatch.h
@@ -0,0 +1,217 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This header contains an interface `FailureLatch`, and some implementation
+// helpers that may be used across a range of classes and functions to handle
+// failures at any point during a process, and share that failure state so that
+// the process may gracefully stop quickly and report the first error.
+//
+// It could be thought as a replacement for C++ exceptions, but it's less strong
+// (cancellations may be delayed).
+// Now, if possible, mozilla::Result may be a better option as C++ exceptions
+// replacement, as it is more visible in all affected functions.
+// Consider FailureLatch if failures may happen in different places, but where
+// `return`ing this potential failure from all functions would be too arduous.
+
+#ifndef mozilla_FailureLatch_h
+#define mozilla_FailureLatch_h
+
+#include <mozilla/Assertions.h>
+
+#include <string>
+
+namespace mozilla {
+
+// ----------------------------------------------------------------------------
+// Main interface
+// ----------------------------------------------------------------------------
+
+// Interface handling a failure latch (starting in a successful state, the first
+// failure gets recorded, subsequent failures are ignored.)
+class FailureLatch {
+ public:
+  virtual ~FailureLatch() = default;
+
+  // Can this ever fail? (This may influence how some code deals with
+  // failures, e.g., if infallible, OOMs should assert&crash.)
+  [[nodiscard]] virtual bool Fallible() const = 0;
+
+  // Set latch in its failed state because of an external cause.
+  // The first call sets the reason, subsequent calls are ignored.
+  virtual void SetFailure(std::string aReason) = 0;
+
+  // Has there been any failure so far?
+  [[nodiscard]] virtual bool Failed() const = 0;
+
+  // Return first failure string, may be null if not failed yet.
+  [[nodiscard]] virtual const char* GetFailure() const = 0;
+
+  // Retrieve the one source FailureLatch. It could reference `*this`!
+  // This may be used by dependent proxy FailureLatch'es to find where to
+  // redirect calls.
+  [[nodiscard]] virtual const FailureLatch& SourceFailureLatch() const = 0;
+  [[nodiscard]] virtual FailureLatch& SourceFailureLatch() = 0;
+
+  // Non-virtual helpers.
+
+  // Transfer any failure from another FailureLatch.
+  void SetFailureFrom(const FailureLatch& aOther) {
+    if (Failed()) {
+      return;
+    }
+    if (const char* otherFailure = aOther.GetFailure(); otherFailure) {
+      SetFailure(otherFailure);
+    }
+  }
+};
+
+// ----------------------------------------------------------------------------
+// Concrete implementations
+// ----------------------------------------------------------------------------
+
+// Concrete infallible FailureLatch class.
+// Any `SetFailure` leads to an assert-crash, so the final runtime result can
+// always be assumed to be succesful.
+class FailureLatchInfallibleSource final : public FailureLatch {
+ public:
+  [[nodiscard]] bool Fallible() const final { return false; }
+
+  void SetFailure(std::string aReason) final {
+    MOZ_RELEASE_ASSERT(false,
+                       "SetFailure in infallible FailureLatchInfallibleSource");
+  }
+
+  [[nodiscard]] bool Failed() const final { return false; }
+
+  [[nodiscard]] const char* GetFailure() const final { return nullptr; }
+
+  [[nodiscard]] const ::mozilla::FailureLatch& SourceFailureLatch()
+      const final {
+    return *this;
+  }
+
+  [[nodiscard]] ::mozilla::FailureLatch& SourceFailureLatch() final {
+    return *this;
+  }
+
+  // Singleton FailureLatchInfallibleSource that may be used as default
+  // FailureLatch proxy.
+  static FailureLatchInfallibleSource& Singleton() {
+    static FailureLatchInfallibleSource singleton;
+    return singleton;
+  }
+};
+
+// Concrete FailureLatch class, intended to be intantiated as an object shared
+// between classes and functions that are part of a long operation, so that
+// failures can happen anywhere and be visible everywhere.
+// Not thread-safe.
+class FailureLatchSource final : public FailureLatch {
+ public:
+  [[nodiscard]] bool Fallible() const final { return true; }
+
+  void SetFailure(std::string aReason) final {
+    if (!mFailed) {
+      mFailed = true;
+      mReason = std::move(aReason);
+    }
+  }
+
+  [[nodiscard]] bool Failed() const final { return mFailed; }
+
+  [[nodiscard]] const char* GetFailure() const final {
+    return mFailed ? mReason.c_str() : nullptr;
+  }
+
+  [[nodiscard]] const FailureLatch& SourceFailureLatch() const final {
+    return *this;
+  }
+
+  [[nodiscard]] FailureLatch& SourceFailureLatch() final { return *this; }
+
+ private:
+  bool mFailed = false;
+  std::string mReason;
+};
+
+// ----------------------------------------------------------------------------
+// Helper macros, to be used in FailureLatch-derived classes
+// ----------------------------------------------------------------------------
+
+// Classes deriving from FailureLatch can use this to forward virtual calls to
+// another FailureLatch.
+#define FAILURELATCH_IMPL_PROXY(FAILURELATCH_REF)                        \
+  [[nodiscard]] bool Fallible() const final {                            \
+    return static_cast<const ::mozilla::FailureLatch&>(FAILURELATCH_REF) \
+        .Fallible();                                                     \
+  }                                                                      \
+  void SetFailure(std::string aReason) final {                           \
+    static_cast<::mozilla::FailureLatch&>(FAILURELATCH_REF)              \
+        .SetFailure(std::move(aReason));                                 \
+  }                                                                      \
+  [[nodiscard]] bool Failed() const final {                              \
+    return static_cast<const ::mozilla::FailureLatch&>(FAILURELATCH_REF) \
+        .Failed();                                                       \
+  }                                                                      \
+  [[nodiscard]] const char* GetFailure() const final {                   \
+    return static_cast<const ::mozilla::FailureLatch&>(FAILURELATCH_REF) \
+        .GetFailure();                                                   \
+  }                                                                      \
+  [[nodiscard]] const FailureLatch& SourceFailureLatch() const final {   \
+    return static_cast<const ::mozilla::FailureLatch&>(FAILURELATCH_REF) \
+        .SourceFailureLatch();                                           \
+  }                                                                      \
+  [[nodiscard]] FailureLatch& SourceFailureLatch() final {               \
+    return static_cast<::mozilla::FailureLatch&>(FAILURELATCH_REF)       \
+        .SourceFailureLatch();                                           \
+  }
+
+// Classes deriving from FailureLatch can use this to forward virtual calls to
+// another FailureLatch through a pointer, unless it's null in which case act
+// like an infallible FailureLatch.
+#define FAILURELATCH_IMPL_PROXY_OR_INFALLIBLE(FAILURELATCH_PTR, CLASS_NAME)    \
+  [[nodiscard]] bool Fallible() const final {                                  \
+    return FAILURELATCH_PTR                                                    \
+               ? static_cast<const ::mozilla::FailureLatch*>(FAILURELATCH_PTR) \
+                     ->Fallible()                                              \
+               : false;                                                        \
+  }                                                                            \
+  void SetFailure(std::string aReason) final {                                 \
+    if (FAILURELATCH_PTR) {                                                    \
+      static_cast<::mozilla::FailureLatch*>(FAILURELATCH_PTR)                  \
+          ->SetFailure(std::move(aReason));                                    \
+    } else {                                                                   \
+      MOZ_RELEASE_ASSERT(false, "SetFailure in infallible " #CLASS_NAME);      \
+    }                                                                          \
+  }                                                                            \
+  [[nodiscard]] bool Failed() const final {                                    \
+    return FAILURELATCH_PTR                                                    \
+               ? static_cast<const ::mozilla::FailureLatch*>(FAILURELATCH_PTR) \
+                     ->Failed()                                                \
+               : false;                                                        \
+  }                                                                            \
+  [[nodiscard]] const char* GetFailure() const final {                         \
+    return FAILURELATCH_PTR                                                    \
+               ? static_cast<const ::mozilla::FailureLatch*>(FAILURELATCH_PTR) \
+                     ->GetFailure()                                            \
+               : nullptr;                                                      \
+  }                                                                            \
+  [[nodiscard]] const FailureLatch& SourceFailureLatch() const final {         \
+    return FAILURELATCH_PTR                                                    \
+               ? static_cast<const ::mozilla::FailureLatch*>(FAILURELATCH_PTR) \
+                     ->SourceFailureLatch()                                    \
+               : ::mozilla::FailureLatchInfallibleSource::Singleton();         \
+  }                                                                            \
+  [[nodiscard]] FailureLatch& SourceFailureLatch() final {                     \
+    return FAILURELATCH_PTR                                                    \
+               ? static_cast<::mozilla::FailureLatch*>(FAILURELATCH_PTR)       \
+                     ->SourceFailureLatch()                                    \
+               : ::mozilla::FailureLatchInfallibleSource::Singleton();         \
+  }
+
+}  // namespace mozilla
+
+#endif /* mozilla_FailureLatch_h */