https://github.com/Teemperor updated https://github.com/llvm/llvm-project/pull/219421
>From 195460634c30c3bfb81a5d6cdb460f70526e15f6 Mon Sep 17 00:00:00 2001 From: Raphael Isemann <[email protected]> Date: Thu, 27 Aug 2026 15:28:32 +0100 Subject: [PATCH] [lldb] Add Guarded<T, Mutex> to Locked.h LLDB's code base has many variables that have an associated mutex that needs to be locked to safely access that variable from multiple threads. However, this locking scheme is currently not enforced by the compiler and code sometimes accesses these variables without aquiring the respective mutex first. This patch introduces a `Guarded` class that strictly enforces that some memory is only accessed after the respective mutex has been aquired. This class hands out `Locked` objects for every access which guarentee that the mutex is held as long as the variable is in scope. --- lldb/include/lldb/Utility/Locked.h | 28 ++++++++++++++++++++ lldb/unittests/Utility/LockedTest.cpp | 37 +++++++++++++++++++++++++++ 2 files changed, 65 insertions(+) diff --git a/lldb/include/lldb/Utility/Locked.h b/lldb/include/lldb/Utility/Locked.h index acd34e454a918..66892e4d9aebb 100644 --- a/lldb/include/lldb/Utility/Locked.h +++ b/lldb/include/lldb/Utility/Locked.h @@ -168,6 +168,34 @@ template <typename T, typename Mutex = llvm::sys::RWMutex> using SharedLockedUP = SharedLocked<std::unique_ptr<const T>, Mutex>; /// @} +/// Bundles a value of type `T` with the `Mutex` that guards it. +/// +/// This class prevents accidential use of a value without aquiring the +/// lock and should be preferred over a member + mutex pair. +/// +/// `Mutex` must satisfy `Lockable` when calling `Lock()` and `SharedLockable` +/// when calling `LockShared()`. +template <typename T, typename Mutex = llvm::sys::RWMutex> class Guarded { +public: + Guarded() = default; + explicit Guarded(T value) : m_value(std::move(value)) {} + + Guarded(const Guarded &) = delete; + Guarded &operator=(const Guarded &) = delete; + + /// Exclusive (read/write) access to the value. + LockedPtr<T, Mutex> Lock() { return LockedPtr<T, Mutex>(m_mutex, &m_value); } + + /// Shared (read-only) access to the value. + SharedLockedPtr<T, Mutex> LockShared() const { + return SharedLockedPtr<T, Mutex>(m_mutex, &m_value); + } + +private: + mutable Mutex m_mutex; + T m_value{}; +}; + } // namespace lldb_private #endif // LLDB_UTILITY_LOCKED_H diff --git a/lldb/unittests/Utility/LockedTest.cpp b/lldb/unittests/Utility/LockedTest.cpp index cae24293dee2e..f898f21b56291 100644 --- a/lldb/unittests/Utility/LockedTest.cpp +++ b/lldb/unittests/Utility/LockedTest.cpp @@ -225,3 +225,40 @@ TEST(LockedTest, ExclusiveAccessOnRWMutex) { writer->value = 11; EXPECT_EQ(widget.value, 11); } + +// Guarded is neither copyable nor movable. +static_assert(!std::is_copy_constructible_v<Guarded<Widget>>); +static_assert(!std::is_move_constructible_v<Guarded<Widget>>); + +TEST(LockedTest, GuardedDefaultConstructed) { + Guarded<Widget> guarded; + EXPECT_EQ(guarded.Lock()->value, 0); +} + +TEST(LockedTest, GuardedValueConstructed) { + Guarded<Widget> guarded(Widget{42}); + EXPECT_EQ(guarded.Lock()->value, 42); +} + +TEST(LockedTest, GuardedExclusiveAccessMutatesValue) { + Guarded<Widget> guarded; + guarded.Lock()->value = 7; + EXPECT_EQ(guarded.Lock()->value, 7); +} + +TEST(LockedTest, GuardedSharedAccessIsReadOnly) { + Guarded<Widget> guarded(Widget{5}); + SharedLocked<const Widget *, llvm::sys::RWMutex> reader = + guarded.LockShared(); + EXPECT_EQ(reader->value, 5); + static_assert(std::is_same_v<decltype(reader.get()), const Widget *>, + "shared access borrows a const-qualified pointer"); +} + +// std::shared_mutex satisfies SharedLockable too, so Guarded works with it +// as a drop-in replacement for llvm::sys::RWMutex. +TEST(LockedTest, GuardedWorksWithStdSharedMutex) { + Guarded<Widget, std::shared_mutex> guarded; + guarded.Lock()->value = 3; + EXPECT_EQ(guarded.LockShared()->value, 3); +} _______________________________________________ lldb-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
