RtlNtStatusToDosError

RtlNtStatusToDosError is a Windows runtime library function used to translate NTSTATUS codes, which originate from the Windows NT kernel and native APIs, into Win32/DOS error codes that are used by standard Win32 error handling. The function takes an NTSTATUS value as input and returns a Windows error code suitable for use with GetLastError. In practice, this enables native API results to be interpreted by higher-level Win32 code and wrappers.

The function is exported by ntdll.dll and is considered part of the Windows Native API. It provides a bridge between the NTSTATUS error model and the Win32 error model, allowing components that return NTSTATUS to produce conventional Win32 error reporting when needed. A successful NTSTATUS value (STATUS_SUCCESS) maps to a success code (typically 0) in Win32 terms.

Mapping behavior typically covers many common NTSTATUS values with direct Win32 equivalents. For example, not-found or access-related statuses are translated to the corresponding Win32 error codes when such equivalents exist. When a direct mapping does not exist, the function returns a general failure code, reflecting that no precise Win32 error mapping is defined for that NTSTATUS value. The exact mappings can vary between Windows versions, reflecting differences in the error model across releases.

Usage notes: RtlNtStatusToDosError is an internal helper used by some system components and wrappers to convert native error results to Win32-style errors. It is not part of the public, documented Win32 API, so portable application code is advised to rely on official Win32 error handling pathways or wrappers rather than depending on its behavior. See also related translation helpers in the Windows Native API.