[Lldb-commits] [lldb] [lldb][windows] keep track of interrupted reads in ConnectionGenericFile (PR #182536)

[Charles Zablit via lldb-commits]

https://github.com/charles-zablit created https://github.com/llvm/llvm-project/pull/182536

If a read is interrupted in `ConnectionGenericFile::Read`, the data that has already been read by `ReadFile` is lost.

This patch adds `m_read_pending` to mark a read as interrupted. The next read will pick up the results of the previous read and return the number of `bytes_read`.

>From f5688837a040f62f54cf1ca98798d4aee56bf105 Mon Sep 17 00:00:00 2001
From: Charles Zablit <c_zablit at apple.com>
Date: Fri, 20 Feb 2026 16:54:17 +0000
Subject: [PATCH] [lldb][windows] keep track of interrupted reads in
 ConnectionGenericFile

---
 .../lldb/Host/windows/ConnectionGenericFileWindows.h   |  1 +
 .../Host/windows/ConnectionGenericFileWindows.cpp      | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/lldb/include/lldb/Host/windows/ConnectionGenericFileWindows.h b/lldb/include/lldb/Host/windows/ConnectionGenericFileWindows.h
index d8f06a7162b22..62ac1bb35c9f8 100644
--- a/lldb/include/lldb/Host/windows/ConnectionGenericFileWindows.h
+++ b/lldb/include/lldb/Host/windows/ConnectionGenericFileWindows.h
@@ -43,6 +43,7 @@ class ConnectionGenericFile : public lldb_private::Connection {
 
 protected:
   OVERLAPPED m_overlapped;
+  bool m_read_pending = false;
   HANDLE m_file;
   HANDLE m_event_handles[2];
   bool m_owns_file;
diff --git a/lldb/source/Host/windows/ConnectionGenericFileWindows.cpp b/lldb/source/Host/windows/ConnectionGenericFileWindows.cpp
index 6a6153d6e34a0..28727c82f6e37 100644
--- a/lldb/source/Host/windows/ConnectionGenericFileWindows.cpp
+++ b/lldb/source/Host/windows/ConnectionGenericFileWindows.cpp
@@ -176,9 +176,17 @@ size_t ConnectionGenericFile::Read(void *dst, size_t dst_len,
     goto finish;
   }
 
+  if (m_read_pending) {
+    if (::GetOverlappedResult(m_file, &m_overlapped, &bytes_read, FALSE)) {
+      m_read_pending = false;
+      return bytes_read;
+    }
+  }
+
   m_overlapped.hEvent = m_event_handles[kBytesAvailableEvent];
 
   result = ::ReadFile(m_file, dst, dst_len, NULL, &m_overlapped);
+  m_read_pending = true;
   if (result || ::GetLastError() == ERROR_IO_PENDING) {
     if (!result) {
       // The expected return path.  The operation is pending.  Wait for the
@@ -234,6 +242,8 @@ size_t ConnectionGenericFile::Read(void *dst, size_t dst_len,
   goto finish;
 
 finish:
+  if (return_info.GetStatus() != eConnectionStatusInterrupted)
+    m_read_pending = false;
   status = return_info.GetStatus();
   if (error_ptr)
     *error_ptr = return_info.GetError().Clone();