Ol mem alloc alignment2 - #2
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…ould be used by both olMemAlloc versions
…backends; going to test on AMD and CUDA
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…198548) When an MCP client disconnects (EOF), `IOTransport::OnRead` called `handler.OnClosed()` before resetting `m_read_handle`. The MCP server's `OnClosed` handler erases the client from `m_instances`, destroying both the transport (`this`) and the binder (`handler`). The subsequent `m_read_handle.reset()` then accessed the destroyed transport's member, causing a use-after-free (SIGSEGV). * thread #1, stop reason = signal SIGSEGV: address not mapped to object (fault address=0x28) * frame #0: 0x00007ff5d4d5afda liblldb.so.23.2`lldb_private::transport::IOTransport<lldb_protocol::mcp::ProtocolDescriptor>::OnRead(lldb_private::MainLoopBase&, lldb_private::transport::JSONTransport<lldb_protocol::mcp::ProtocolDescriptor>::MessageHandler&) + 1274 frame #1: 0x00007ff5d1140ad8 liblldb.so.23.0`lldb_private::MainLoopPosix::Run() + 408 frame #2: 0x00007ff5d1760c1c liblldb.so.23.0`std::thread::_State_impl<std::thre Fix by resetting the read handle before calling `OnClosed()`, so no transport members are accessed after the handler potentially destroys the transport. Then when the scope is left, the destructor is called for the new read_handle local variable and it is cleaned up. New unit tests added that fail without this change. With the change, the custom 'ai' script (allows end user locally to communicate lldb context to agent backend via a spun up MCP server: "protocol-server start MCP listen://localhost:{port}") now successfully concludes without this crash Assisted with: claude
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Fix llvm#201615. Fix the issue that non atomic operations race in waiting queue, which causes missed futex wakeup signals. Confirmed by TSAN: ``` ================== WARNING: ThreadSanitizer: data race (pid=388518) Write of size 4 at 0x7ffd21cf98e4 by thread T23: #0 __llvm_libc_23_0_0_git::RawRwLock::notify_pending_threads() ./libc/src/__support/threads/raw_rwlock.h:443:44 #1 __llvm_libc_23_0_0_git::RawRwLock::unlock() ./libc/src/__support/threads/raw_rwlock.h:520:5 #2 randomized_thread_operation(SharedData*) ./libc/test/integration/src/__support/threads/tsan_full_rwlock.cpp:104:18 #3 thread_runner(void*) ./libc/test/integration/src/__support/threads/tsan_full_rwlock.cpp:148:5 Previous atomic read of size 4 at 0x7ffd21cf98e4 by thread T4: #0 __llvm_libc_23_0_0_git::cpp::Atomic<unsigned int>::load(...) ./libc/src/__support/CPP/atomic.h:115:5 #1 __llvm_libc_23_0_0_git::Futex::wait(...) ./libc/src/__support/threads/linux/futex_utils.h:43:17 #2 __llvm_libc_23_0_0_git::cpp::expected<int, int> __llvm_libc_23_0_0_git::rwlock::WaitingQueue::wait<Role::Reader>(...) ./libc/src/__support/threads/raw_rwlock.h:101:35 #3 __llvm_libc_23_0_0_git::rwlock::LockResult __llvm_libc_23_0_0_git::RawRwLock::lock_slow<Role::Reader>(...) ./libc/src/__support/threads/raw_rwlock.h:402:34 #4 __llvm_libc_23_0_0_git::RawRwLock::read_lock(...) ./libc/src/__support/threads/raw_rwlock.h:485:12 #5 randomized_thread_operation(SharedData*) ./libc/test/integration/src/__support/threads/tsan_full_rwlock.cpp:79:16 llvm#6 thread_runner(void*) ./libc/test/integration/src/__support/threads/tsan_full_rwlock.cpp:148:5 Thread T23 (tid=388553, running) created by main thread at: #0 pthread_create ... #1 main ./libc/test/integration/src/__support/threads/tsan_full_rwlock.cpp:166:5 Thread T4 (tid=388533, running) created by main thread at: #0 pthread_create ... #1 main ./libc/test/integration/src/__support/threads/tsan_full_rwlock.cpp:166:5 SUMMARY: ThreadSanitizer: data race ./libc/src/__support/threads/raw_rwlock.h:443:44 in __llvm_libc_23_0_0_git::RawRwLock::notify_pending_threads() ================== ``` AI wrote the detection script. Manually fixed.
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I recently noticed LLDB crash during execution of `script print(lldb.SBDebugger().GetBroadcaster().GetName())` command: ``` PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace. Stack dump: 0. Program arguments: /home/sergei/llvm-project/build/bin/lldb-dap #0 0x000062735c3403d2 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/sergei/llvm-project/build/bin/lldb-dap+0x7c3d2) #1 0x000062735c33d7ec llvm::sys::RunSignalHandlers() (/home/sergei/llvm-project/build/bin/lldb-dap+0x797ec) #2 0x000062735c33d94c SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0 #3 0x00007eaa6aa45330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330) #4 0x00007eaa6bb0c092 lldb::SBBroadcaster::GetName() const (/home/sergei/llvm-project/build/bin/../lib/liblldb.so.23.0git+0x90c092) #5 0x00007eaa6bcb9a5d _wrap_SBBroadcaster_GetName LLDBWrapPython.cpp:0:0 llvm#6 0x00007eaa6a1df5f5 (/lib/x86_64-linux-gnu/libpython3.12.so.1.0+0x1df5f5) llvm#7 0x00007eaa6a182b2c PyObject_Vectorcall (/lib/x86_64-linux-gnu/libpython3.12.so.1.0+0x182b2c) llvm#8 0x00007eaa6a11d5ee _PyEval_EvalFrameDefault (/lib/x86_64-linux-gnu/libpython3.12.so.1.0+0x11d5ee) llvm#9 0x00007eaa6a2a091f PyEval_EvalCode (/lib/x86_64-linux-gnu/libpython3.12.so.1.0+0x2a091f) llvm#10 0x00007eaa6a29c8b0 (/lib/x86_64-linux-gnu/libpython3.12.so.1.0+0x29c8b0) llvm#11 0x00007eaa6a11fbd3 _PyEval_EvalFrameDefault (/lib/x86_64-linux-gnu/libpython3.12.so.1.0+0x11fbd3) llvm#12 0x00007eaa6c4891b7 lldb_private::ScriptInterpreterPythonImpl::ExecuteOneLine(llvm::StringRef, lldb_private::CommandReturnObject*, lldb_private::ExecuteScriptOptions const&) (/home/sergei/llvm-project/build/bin/../lib/liblldb.so.23.0git+0x12891b7) llvm#13 0x00007eaa70326ff5 CommandObjectScriptingRun::DoExecute(llvm::StringRef, lldb_private::CommandReturnObject&) (/home/sergei/llvm-project/build/bin/../lib/liblldb.so.23.0git+0x5126ff5) llvm#14 0x00007eaa6bee3739 lldb_private::CommandObjectRaw::Execute(char const*, lldb_private::CommandReturnObject&) (/home/sergei/llvm-project/build/bin/../lib/liblldb.so.23.0git+0xce3739) llvm#15 0x00007eaa6bede09a lldb_private::CommandInterpreter::HandleCommand(char const*, lldb_private::LazyBool, lldb_private::CommandReturnObject&, bool) (/home/sergei/llvm-project/build/bin/../lib/liblldb.so.23.0git+0xcde09a) llvm#16 0x00007eaa6bb0f0f8 lldb::SBCommandInterpreter::HandleCommand(char const*, lldb::SBExecutionContext&, lldb::SBCommandReturnObject&, bool) (/home/sergei/llvm-project/build/bin/../lib/liblldb.so.23.0git+0x90f0f8) llvm#17 0x00007eaa6bb0f265 lldb::SBCommandInterpreter::HandleCommand(char const*, lldb::SBCommandReturnObject&, bool) (/home/sergei/llvm-project/build/bin/../lib/liblldb.so.23.0git+0x90f265) llvm#18 0x000062735c3707f3 lldb_dap::RunLLDBCommands[abi:cxx11](lldb::SBDebugger&, lldb::SBMutex, llvm::StringRef, llvm::ArrayRef<lldb_dap::protocol::String> const&, bool&, bool, bool) (/home/sergei/llvm-project/build/bin/lldb-dap+0xac7f3) llvm#19 0x000062735c3a8019 lldb_dap::EvaluateRequestHandler::Run(lldb_dap::protocol::EvaluateArguments const&) const (/home/sergei/llvm-project/build/bin/lldb-dap+0xe4019) llvm#20 0x000062735c3aba78 lldb_dap::RequestHandler<lldb_dap::protocol::EvaluateArguments, llvm::Expected<lldb_dap::protocol::EvaluateResponseBody>>::operator()(lldb_dap::protocol::Request const&) const (/home/sergei/llvm-project/build/bin/lldb-dap+0xe7a78) llvm#21 0x000062735c3ce1bf lldb_dap::BaseRequestHandler::Run(lldb_dap::protocol::Request const&) (/home/sergei/llvm-project/build/bin/lldb-dap+0x10a1bf) llvm#22 0x000062735c3577e7 lldb_dap::DAP::HandleObject(std::variant<lldb_dap::protocol::Request, lldb_dap::protocol::Response, lldb_dap::protocol::Event> const&) (/home/sergei/llvm-project/build/bin/lldb-dap+0x937e7) llvm#23 0x000062735c358705 lldb_dap::DAP::Loop() (/home/sergei/llvm-project/build/bin/lldb-dap+0x94705) llvm#24 0x000062735c2ed0c7 main (/home/sergei/llvm-project/build/bin/lldb-dap+0x290c7) llvm#25 0x00007eaa6aa2a1ca __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3 ``` As far as I understand default constuctors should be covered by fuzzing tests, so I don't know how to write test for that patch.
EuphoricThinking
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Jul 27, 2026
```
void test2() {
__builtin_trap();
}
```
Previously, this would generate this:
```
; Function Attrs: mustprogress noinline nounwind optnone uwtable
define dso_local void @test2()() #2 !dbg !14 {
call void @llvm.trap(), !dbg !15
ret void, !dbg !16
}
```
Now we'll have `unreachable` after the trap
```
; Function Attrs: noinline nounwind optnone uwtable
define dso_local void @test2() #0 {
call void @llvm.trap()
unreachable
}
```
EuphoricThinking
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Jul 27, 2026
llvm#211958) …10739)" This reverts commit 580604f.
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