3 files changed, 70 insertions, 6 deletions

diff --git a/lldb/source/Host/common/Host.cpp b/lldb/source/Host/common/Host.cpp
index 5992b54..510f9c7 100644
--- a/lldb/source/Host/common/Host.cpp
+++ b/lldb/source/Host/common/Host.cpp
@@ -82,10 +82,11 @@ int __pthread_fchdir(int fildes);
 using namespace lldb;
 using namespace lldb_private;
 
-#if !defined(__APPLE__)
-// The system log is currently only meaningful on Darwin, where this means
-// os_log. The meaning of a "system log" isn't as clear on other platforms, and
-// therefore we don't providate a default implementation. Vendors are free to
+#if !defined(__APPLE__) && !defined(_WIN32)
+// The system log is currently only meaningful on Darwin and Windows.
+// On Darwin, this means os_log. On Windows this means Events Viewer.
+// The meaning of a "system log" isn't as clear on other platforms, and
+// therefore we don't providate a default implementation. Vendors are free
 // to implement this function if they have a use for it.
 void Host::SystemLog(Severity severity, llvm::StringRef message) {}
 #endif
diff --git a/lldb/source/Host/windows/Host.cpp b/lldb/source/Host/windows/Host.cpp
index a7369e7..4e747f7 100644
--- a/lldb/source/Host/windows/Host.cpp
+++ b/lldb/source/Host/windows/Host.cpp
@@ -22,7 +22,9 @@
 #include "lldb/Utility/StreamString.h"
 #include "lldb/Utility/StructuredData.h"
 
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/ConvertUTF.h"
+#include "llvm/Support/ManagedStatic.h"
 
 // Windows includes
 #include <tlhelp32.h>
@@ -302,3 +304,64 @@ Environment Host::GetEnvironment() {
   }
   return env;
 }
+
+/// Manages the lifecycle of a Windows Event's Source.
+/// The destructor will call DeregisterEventSource.
+/// This class is meant to be used with \ref llvm::ManagedStatic.
+class WindowsEventLog {
+public:
+  WindowsEventLog() : handle(RegisterEventSource(nullptr, L"lldb")) {}
+
+  ~WindowsEventLog() {
+    if (handle)
+      DeregisterEventSource(handle);
+  }
+
+  HANDLE GetHandle() const { return handle; }
+
+private:
+  HANDLE handle;
+};
+
+static llvm::ManagedStatic<WindowsEventLog> event_log;
+
+static std::wstring AnsiToUtf16(const std::string &ansi) {
+  if (ansi.empty())
+    return {};
+
+  const int unicode_length =
+      MultiByteToWideChar(CP_ACP, 0, ansi.c_str(), -1, nullptr, 0);
+  if (unicode_length == 0)
+    return {};
+
+  std::wstring unicode(unicode_length, L'\0');
+  MultiByteToWideChar(CP_ACP, 0, ansi.c_str(), -1, &unicode[0], unicode_length);
+  return unicode;
+}
+
+void Host::SystemLog(Severity severity, llvm::StringRef message) {
+  HANDLE h = event_log->GetHandle();
+  if (!h)
+    return;
+
+  std::wstring wide_message = AnsiToUtf16(message.str());
+  if (wide_message.empty())
+    return;
+
+  LPCWSTR msg_ptr = wide_message.c_str();
+
+  WORD event_type;
+  switch (severity) {
+  case lldb::eSeverityWarning:
+    event_type = EVENTLOG_WARNING_TYPE;
+    break;
+  case lldb::eSeverityError:
+    event_type = EVENTLOG_ERROR_TYPE;
+    break;
+  case lldb::eSeverityInfo:
+  default:
+    event_type = EVENTLOG_INFORMATION_TYPE;
+  }
+
+  ReportEventW(h, event_type, 0, 0, nullptr, 1, 0, &msg_ptr, nullptr);
+}
diff --git a/lldb/source/Host/windows/MainLoopWindows.cpp b/lldb/source/Host/windows/MainLoopWindows.cpp
index c1a0182..c0b1079 100644
--- a/lldb/source/Host/windows/MainLoopWindows.cpp
+++ b/lldb/source/Host/windows/MainLoopWindows.cpp
@@ -223,7 +223,7 @@ MainLoopWindows::RegisterReadObject(const IOObjectSP &object_sp,
 
   if (m_read_fds.find(waitable_handle) != m_read_fds.end()) {
     error = Status::FromErrorStringWithFormat(
-        "File descriptor %d already monitored.", waitable_handle);
+        "File descriptor %p already monitored.", waitable_handle);
     return nullptr;
   }
 
@@ -235,7 +235,7 @@ MainLoopWindows::RegisterReadObject(const IOObjectSP &object_sp,
   } else {
     DWORD file_type = GetFileType(waitable_handle);
     if (file_type != FILE_TYPE_PIPE) {
-      error = Status::FromErrorStringWithFormat("Unsupported file type %d",
+      error = Status::FromErrorStringWithFormat("Unsupported file type %ld",
                                                 file_type);
       return nullptr;
     }