https://github.com/Teemperor created https://github.com/llvm/llvm-project/pull/219428
Use Guarded to make sure m_vtable_info_map cannot be accesses without locking the respective lock. >From d5fc2112dc99bc54f2e27388eb079a0e5535f61d Mon Sep 17 00:00:00 2001 From: Raphael Isemann <[email protected]> Date: Thu, 27 Aug 2026 15:28:32 +0100 Subject: [PATCH 1/2] [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..f5d7b1aa8e4d9 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. + Locked<T *, Mutex> Lock() { return Locked<T *, Mutex>(m_mutex, &m_value); } + + /// Shared (read-only) access to the value. + SharedLocked<const T *, Mutex> LockShared() const { + return SharedLocked<const 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); +} >From 2f8abf0dbfabfe91c9adf0f713c393121f50413c Mon Sep 17 00:00:00 2001 From: Raphael Isemann <[email protected]> Date: Thu, 27 Aug 2026 15:46:58 +0100 Subject: [PATCH 2/2] [lldb] Use Guarded in CPPLanguageRuntime Use Guarded to make sure m_vtable_info_map cannot be accesses without locking the respective lock. --- .../LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp | 9 ++++----- .../LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h | 5 +++-- 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp index e562266e80d23..27aa2ce07a374 100644 --- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp +++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp @@ -806,9 +806,9 @@ CPPLanguageRuntime::GetVTableInfoEntry(ValueObject &in_value, bool check_type) { // Check our cache first to see if we already have this info { - std::lock_guard<std::mutex> locker(m_vtable_mutex); - auto pos = m_vtable_info_map.find(vtable_addr); - if (pos != m_vtable_info_map.end()) + auto vtable_info_map = m_vtable_info_map.Lock(); + auto pos = vtable_info_map->find(vtable_addr); + if (pos != vtable_info_map->end()) return pos->second; } @@ -830,8 +830,7 @@ CPPLanguageRuntime::GetVTableInfoEntry(ValueObject &in_value, bool check_type) { /*info=*/VTableInfo{vtable_addr, symbol}, /*runtime=*/runtime.get(), }; - std::lock_guard<std::mutex> locker(m_vtable_mutex); - m_vtable_info_map[vtable_addr] = entry; + (*m_vtable_info_map.Lock())[vtable_addr] = entry; return entry; } } diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h index 823a968cbad8c..5bc21448ce306 100644 --- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h +++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h @@ -16,6 +16,7 @@ #include "CommonABIRuntime.h" #include "lldb/Core/PluginInterface.h" #include "lldb/Target/LanguageRuntime.h" +#include "lldb/Utility/Locked.h" #include "lldb/lldb-private.h" namespace lldb_private { @@ -153,8 +154,8 @@ class CPPLanguageRuntime : public LanguageRuntime { llvm::Expected<VTableInfoEntry> GetVTableInfoEntry(ValueObject &in_value, bool check_type); - std::map<Address, VTableInfoEntry> m_vtable_info_map; - std::mutex m_vtable_mutex; + using VTableInfoMap = std::map<Address, VTableInfoEntry>; + Guarded<VTableInfoMap, std::mutex> m_vtable_info_map; }; } // namespace lldb_private _______________________________________________ lldb-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
