[Lldb-commits] [lldb] a335f33 - [lldb] Always lock in StreamLogHandler::Write (#205771)

[via lldb-commits]

Author: Raphael Isemann
Date: 2026-06-26T11:22:21+01:00
New Revision: a335f334f512be44ac02a07ffae27468d246a07d

URL: https://github.com/llvm/llvm-project/commit/a335f334f512be44ac02a07ffae27468d246a07d
DIFF: https://github.com/llvm/llvm-project/commit/a335f334f512be44ac02a07ffae27468d246a07d.diff

LOG: [lldb] Always lock in StreamLogHandler::Write (#205771)

This code assumes that writing to an unbuffered raw_fd_ostream from
multiple threads is somehow safe. raw_fd_ostream doesn't make any
guarantees about this from what I can see.

The current raw_fd_ostream implementation also uses a looping write call
to write the content in chunks, and doing this from multiple threads
leads to interleaving log messages.

This patch unconditionally make us aquire the stream lock.

Added: 
    

Modified: 
    lldb/source/Utility/Log.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/source/Utility/Log.cpp b/lldb/source/Utility/Log.cpp
index 1921573996196..6b077a3766e9f 100644
--- a/lldb/source/Utility/Log.cpp
+++ b/lldb/source/Utility/Log.cpp
@@ -378,12 +378,8 @@ void StreamLogHandler::Flush() {
 }
 
 void StreamLogHandler::Emit(llvm::StringRef message) {
-  if (m_stream.GetBufferSize() > 0) {
-    std::lock_guard<std::mutex> guard(m_mutex);
-    m_stream << message;
-  } else {
-    m_stream << message;
-  }
+  std::lock_guard<std::mutex> guard(m_mutex);
+  m_stream << message;
 }
 
 CallbackLogHandler::CallbackLogHandler(lldb::LogOutputCallback callback,