[Support] Handle delete_pending case for Windows fs::status (#90655)

If a delete is pending on the file queried for status, a misleading
`permission_denied` error code will be returned (this is the correct
mapping of the error set by GetFileAttributesW). By querying the
underlying NTSTATUS code via ntdll's RtlGetLastNtStatus, this case can
be disambiguated. If this underlying error code indicates a pending
delete, fs::status will return a new `pending_delete` error code to be
handled by callers

Fixes #89137

Author: z2oh

llvm/include/llvm/Support/Errc.h

@@ -38,6 +38,10 @@ enum class errc {
   bad_address = int(std::errc::bad_address),
   bad_file_descriptor = int(std::errc::bad_file_descriptor),
   broken_pipe = int(std::errc::broken_pipe),
+  // There is no delete_pending in std::errc; this error code is negative to
+  // avoid conflicts. This error roughly corresponds with Windows'
+  // STATUS_DELETE_PENDING 0xC0000056.
+  delete_pending = -56,
   device_or_resource_busy = int(std::errc::device_or_resource_busy),
   directory_not_empty = int(std::errc::directory_not_empty),
   executable_format_error = int(std::errc::executable_format_error),

llvm/include/llvm/Support/WindowsError.h

@@ -12,6 +12,7 @@
 #include <system_error>
 
 namespace llvm {
+std::error_code mapLastWindowsError();
 std::error_code mapWindowsError(unsigned EV);
 }
 

llvm/lib/Support/CMakeLists.txt

@@ -40,7 +40,8 @@ endif()
 if( MSVC OR MINGW )
   # libuuid required for FOLDERID_Profile usage in lib/Support/Windows/Path.inc.
   # advapi32 required for CryptAcquireContextW in lib/Support/Windows/Path.inc.
-  set(system_libs ${system_libs} psapi shell32 ole32 uuid advapi32 ws2_32)
+  # ntdll required for RtlGetLastNtStatus in lib/Support/ErrorHandling.cpp.
+  set(system_libs ${system_libs} psapi shell32 ole32 uuid advapi32 ws2_32 ntdll)
 elseif( CMAKE_HOST_UNIX )
   if( HAVE_LIBRT )
     set(system_libs ${system_libs} rt)

llvm/lib/Support/ErrorHandling.cpp

@@ -236,8 +236,43 @@ void LLVMResetFatalErrorHandler() {
 
 #ifdef _WIN32
 
+#define WIN32_NO_STATUS
+#include "llvm/Support/Windows/WindowsSupport.h"
+#undef WIN32_NO_STATUS
+#include <ntstatus.h>
 #include <winerror.h>
 
+// This is equivalent to NtCurrentTeb()->LastStatusValue, but the public
+// _TEB definition does not expose the LastStatusValue field directly.
+// Avoid offsetting into this structure by calling RtlGetLastNtStatus
+// from ntdll.dll.
+//
+// The return of this function will roughly match that of
+// GetLastError, but this lower level API disambiguates some cases
+// that GetLastError does not.
+//
+// For more information, see:
+// https://www.geoffchappell.com/studies/windows/km/ntoskrnl/inc/api/pebteb/teb/index.htm
+// https://github.com/llvm/llvm-project/issues/89137
+extern "C" NTSYSAPI NTSTATUS NTAPI RtlGetLastNtStatus();
+
+// This function obtains the last error code and maps it. It may call
+// RtlGetLastNtStatus, which is a lower level API that can return a
+// more specific error code than GetLastError.
+std::error_code llvm::mapLastWindowsError() {
+  unsigned EV = ::GetLastError();
+  // The mapping of NTSTATUS to Win32 error loses some information; special
+  // case the generic ERROR_ACCESS_DENIED code to check the underlying
+  // NTSTATUS and potentially return a more accurate error code.
+  if (EV == ERROR_ACCESS_DENIED) {
+    llvm::errc code = RtlGetLastNtStatus() == STATUS_DELETE_PENDING
+                          ? errc::delete_pending
+                          : errc::permission_denied;
+    return make_error_code(code);
+  }
+  return mapWindowsError(EV);
+}
+
 // I'd rather not double the line count of the following.
 #define MAP_ERR_TO_COND(x, y)                                                  \
   case x:                                                                      \

llvm/lib/Support/Windows/Path.inc

@@ -760,14 +760,14 @@ static std::error_code getStatus(HANDLE FileHandle, file_status &Result) {
   return std::error_code();
 
 handle_status_error:
-  DWORD LastError = ::GetLastError();
-  if (LastError == ERROR_FILE_NOT_FOUND || LastError == ERROR_PATH_NOT_FOUND)
+  std::error_code Err = mapLastWindowsError();
+  if (Err == std::errc::no_such_file_or_directory)
     Result = file_status(file_type::file_not_found);
-  else if (LastError == ERROR_SHARING_VIOLATION)
+  else if (Err == std::errc::permission_denied)
     Result = file_status(file_type::type_unknown);
   else
     Result = file_status(file_type::status_error);
-  return mapWindowsError(LastError);
+  return Err;
 }
 
 std::error_code status(const Twine &path, file_status &result, bool Follow) {