[lldb][windows] use Windows APIs to print to the console (#149493)

charles-zablit · web-flow · commit f55dc0824ebc · 2025-08-19T14:52:29.000+01:00
This patch uses the Windows APIs to print to the Windows Console, through `llvm::raw_fd_ostream`. This fixes a rendering issue where the characters defined in `DiagnosticsRendering.cpp` (`"╰"` for instance) are not rendered properly on Windows out of the box, because the default codepage is not `utf-8`. This solution is based on [this patch downstream](https://github.com/swiftlang/swift/pull/40632/files#diff-e948e4bd7a601e3ca82d596058ccb39326459a4751470eec4d393adeaf516977R37-R38). rdar://156064500
diff --git a/lldb/include/lldb/Host/File.h b/lldb/include/lldb/Host/File.h
@@ -382,15 +382,11 @@ class NativeFile : public File {
     Unowned = false,
   };
 
-  NativeFile() : m_descriptor(kInvalidDescriptor), m_stream(kInvalidStream) {}
+  NativeFile();
 
-  NativeFile(FILE *fh, bool transfer_ownership)
-      : m_descriptor(kInvalidDescriptor), m_own_descriptor(false), m_stream(fh),
-        m_options(), m_own_stream(transfer_ownership) {}
+  NativeFile(FILE *fh, bool transfer_ownership);
 
-  NativeFile(int fd, OpenOptions options, bool transfer_ownership)
-      : m_descriptor(fd), m_own_descriptor(transfer_ownership),
-        m_stream(kInvalidStream), m_options(options), m_own_stream(false) {}
+  NativeFile(int fd, OpenOptions options, bool transfer_ownership);
 
   ~NativeFile() override { Close(); }
 
@@ -444,17 +440,19 @@ class NativeFile : public File {
     return ValueGuard(m_stream_mutex, StreamIsValidUnlocked());
   }
 
-  int m_descriptor;
+  int m_descriptor = kInvalidDescriptor;
   bool m_own_descriptor = false;
   mutable std::mutex m_descriptor_mutex;
 
-  FILE *m_stream;
+  FILE *m_stream = kInvalidStream;
   mutable std::mutex m_stream_mutex;
 
   OpenOptions m_options{};
   bool m_own_stream = false;
   std::mutex offset_access_mutex;
 
+  bool is_windows_console = false;
+
 private:
   NativeFile(const NativeFile &) = delete;
   const NativeFile &operator=(const NativeFile &) = delete;
diff --git a/lldb/source/Host/common/File.cpp b/lldb/source/Host/common/File.cpp
@@ -36,6 +36,7 @@
 #include "llvm/Support/Errno.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Process.h"
+#include "llvm/Support/raw_ostream.h"
 
 using namespace lldb;
 using namespace lldb_private;
@@ -247,6 +248,32 @@ uint32_t File::GetPermissions(Status &error) const {
   return file_stats.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO);
 }
 
+NativeFile::NativeFile() = default;
+
+NativeFile::NativeFile(FILE *fh, bool transfer_ownership)
+    : m_stream(fh), m_own_stream(transfer_ownership) {
+#ifdef _WIN32
+  // In order to properly display non ASCII characters in Windows, we need to
+  // use Windows APIs to print to the console. This is only required if the
+  // stream outputs to a console.
+  int fd = _fileno(fh);
+  is_windows_console =
+      ::GetFileType((HANDLE)::_get_osfhandle(fd)) == FILE_TYPE_CHAR;
+#endif
+}
+
+NativeFile::NativeFile(int fd, OpenOptions options, bool transfer_ownership)
+    : m_descriptor(fd), m_own_descriptor(transfer_ownership),
+      m_options(options) {
+#ifdef _WIN32
+  // In order to properly display non ASCII characters in Windows, we need to
+  // use Windows APIs to print to the console. This is only required if the
+  // file outputs to a console.
+  is_windows_console =
+      ::GetFileType((HANDLE)::_get_osfhandle(fd)) == FILE_TYPE_CHAR;
+#endif
+}
+
 bool NativeFile::IsValid() const {
   std::scoped_lock<std::mutex, std::mutex> lock(m_descriptor_mutex, m_stream_mutex);
   return DescriptorIsValidUnlocked() || StreamIsValidUnlocked();
@@ -618,6 +645,12 @@ Status NativeFile::Write(const void *buf, size_t &num_bytes) {
 
   ssize_t bytes_written = -1;
   if (ValueGuard descriptor_guard = DescriptorIsValid()) {
+#ifdef _WIN32
+    if (is_windows_console) {
+      llvm::raw_fd_ostream(m_descriptor, false).write((char *)buf, num_bytes);
+      return error;
+    }
+#endif
     bytes_written =
         llvm::sys::RetryAfterSignal(-1, ::write, m_descriptor, buf, num_bytes);
     if (bytes_written == -1) {
@@ -629,6 +662,13 @@ Status NativeFile::Write(const void *buf, size_t &num_bytes) {
   }
 
   if (ValueGuard stream_guard = StreamIsValid()) {
+#ifdef _WIN32
+    if (is_windows_console) {
+      llvm::raw_fd_ostream(_fileno(m_stream), false)
+          .write((char *)buf, num_bytes);
+      return error;
+    }
+#endif
     bytes_written = ::fwrite(buf, 1, num_bytes, m_stream);
 
     if (bytes_written == 0) {
