https://github.com/charles-zablit created
https://github.com/llvm/llvm-project/pull/150213
This patch makes LLDB use the Event Viewer on Windows (equivalent of system
logging on Darwin) rather than piping to the standard output (which was
deactivated in ca0a5247004b6d692978d10bdbf86e338133e60c.
>From 7a96f44bd01d5a66f18af43d98f4b1ab8776a203 Mon Sep 17 00:00:00 2001
From: Charles Zablit <c_zab...@apple.com>
Date: Wed, 23 Jul 2025 12:43:38 +0100
Subject: [PATCH] [windows][lldb] implement system logging on Windows
---
lldb/include/lldb/Host/Host.h | 4 ++
lldb/source/Host/common/Host.cpp | 21 +++++++++--
lldb/source/Host/windows/Host.cpp | 63 +++++++++++++++++++++++++++++++
3 files changed, 84 insertions(+), 4 deletions(-)
diff --git a/lldb/include/lldb/Host/Host.h b/lldb/include/lldb/Host/Host.h
index 4e19d15b06743..fcabb4fc28315 100644
--- a/lldb/include/lldb/Host/Host.h
+++ b/lldb/include/lldb/Host/Host.h
@@ -109,6 +109,10 @@ class Host {
/// Emit the given message to the operating system log.
static void SystemLog(lldb::Severity severity, llvm::StringRef message);
+ /// Emit the given message to the stdout or stderr depending on severity.
+ static void SystemLogFallback(lldb::Severity severity,
+ llvm::StringRef message);
+
/// Get the process ID for the calling process.
///
/// \return
diff --git a/lldb/source/Host/common/Host.cpp b/lldb/source/Host/common/Host.cpp
index 5992b54318f73..d2737c23313a4 100644
--- a/lldb/source/Host/common/Host.cpp
+++ b/lldb/source/Host/common/Host.cpp
@@ -82,14 +82,27 @@ 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
+void Host::SystemLogFallback(Severity severity, llvm::StringRef message) {
+ switch (severity) {
+ case lldb::eSeverityInfo:
+ case lldb::eSeverityWarning:
+ llvm::outs() << message;
+ return;
+ case lldb::eSeverityError:
+ llvm::errs() << message;
+ return;
+ }
+}
+
static constexpr Log::Category g_categories[] = {
{{"system"}, {"system log"}, SystemLog::System}};
diff --git a/lldb/source/Host/windows/Host.cpp
b/lldb/source/Host/windows/Host.cpp
index a7369e7eade3b..38c862e968302 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 LPCWSTR AnsiToUtf16(const std::string &ansi) {
+ if (ansi.empty())
+ return nullptr;
+ const int unicode_length =
+ MultiByteToWideChar(CP_ACP, 0, ansi.c_str(), -1, nullptr, 0);
+ WCHAR *unicode = new WCHAR[unicode_length];
+ MultiByteToWideChar(CP_ACP, 0, ansi.c_str(), -1, unicode, unicode_length);
+ return unicode;
+}
+
+void Host::SystemLog(Severity severity, llvm::StringRef message) {
+ HANDLE h = event_log->GetHandle();
+ if (!h) {
+ SystemLogFallback(severity, message);
+ return;
+ }
+
+ LPCWSTR wide_message = AnsiToUtf16(message.str());
+ if (!wide_message) {
+ SystemLogFallback(severity, message);
+ return;
+ }
+
+ 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, &wide_message, nullptr);
+
+ delete[] wide_message;
+}
\ No newline at end of file
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