ntresult

Lightweight NTSTATUS-based error handling for Windows kernel-mode Rust code.

ntresult provides a minimal and idiomatic interface for working with Windows NTSTATUS values in Rust, designed specifically for #![no_std] and kernel-mode environments. It bridges native Windows status codes with Rust's Result type without introducing unnecessary abstraction or overhead.

---

Highlights

• #![no_std] support (optional alloc)
• Builds on stable Rust (nightly only for the opt-in allocator-api feature)
• Zero-cost abstraction over NTSTATUS
• Transparent Error and Status wrappers
• Idiomatic Result-based API
• Explicit handling of expected status values
• Severity, facility and code inspection
• Shorthand macros for the common conversions
• No memory allocations
• No unsafe code

---

Feature flags

All features are additive: each one only adds a From conversion into Error. Enabling a feature never changes the behaviour of an existing conversion.

Feature	Default	Toolchain	Conversion added
alloc	no	stable	alloc::collections::TryReserveError
allocator-api	no	nightly	core::alloc::AllocError

Conversions that need nothing beyond core — core::num::TryFromIntError and core::net::AddrParseError — are always available and are not gated behind a feature.

There are no default features. Enabling alloc links the alloc crate, which makes rustc require a #[global_allocator] from the final artifact — a driver, a staticlib — even if nothing ever allocates. A driver that only wants the NTSTATUS wrapper should not be made to supply one, so alloc is opt-in.

allocator-api enables the unstable allocator_api language feature and therefore requires a nightly compiler. Everything else builds on stable Rust.

allocator-api does not imply alloc: AllocError is defined in core, so a driver using a custom Allocator without a global allocator can still use it.

# stable, no allocator required
ntresult = "0.1"

# stable, plus the TryReserveError conversion
# (needs a #[global_allocator] in the final artifact)
ntresult = { version = "0.1", features = ["alloc"] }

# nightly, everything
ntresult = { version = "0.1", features = ["alloc", "allocator-api"] }

---

Core Types

Result<T>

pub type Result<T, E = Error> = core::result::Result<T, E>;

Error

#[derive(Clone, Copy, PartialEq, Eq, Hash)]
#[repr(transparent)]
pub struct Error(pub(crate) NTSTATUS);

impl core::error::Error for Error {}

Debug and Display are hand-written rather than derived — see Formatting.

Status

#[derive(Clone, Copy, PartialEq, Eq, Hash)]
#[repr(transparent)]
pub struct Status(NTSTATUS);

The same data as Error, with the opposite intent: a status that is an expected outcome rather than a failure. It exposes an identical set of accessors.

Usage

Converting NTSTATUS → Result

use ntresult::IntoResult;
use windows_sys::Win32::Foundation::{NTSTATUS, STATUS_SUCCESS};

// Stand-in for a kernel API returning a raw status.
fn some_kernel_call() -> NTSTATUS {
    STATUS_SUCCESS
}

fn my_func() -> ntresult::Result<()> {
    some_kernel_call().into_result()
}

assert!(my_func().is_ok());

NTSTATUS	ntresult::Result<()>
STATUS_SUCCESS	Ok(())
any other code	Err(Error(NTSTATUS))

ntresult intentionally treats all non-STATUS_SUCCESS values as errors. This preserves strict semantics and avoids ambiguity.

Returning NTSTATUS from Result

use ntresult::NtStatus;
use windows_sys::Win32::Foundation::STATUS_SUCCESS;

fn driver_fn() -> ntresult::Result<()> {
    Ok(())
}

assert_eq!(driver_fn().ntstatus(), STATUS_SUCCESS);

ntresult::Result<()>	NTSTATUS
Ok(())	STATUS_SUCCESS
Err(Error(status))	status

Returning an arbitrary data type

When the Ok payload is data rather than a status, use ntstatus_or_success(). The name states that the payload is discarded.

use ntresult::NtStatusOrSuccess;
use windows_sys::Win32::Foundation::STATUS_SUCCESS;

fn read_register() -> ntresult::Result<u32> {
    Ok(0x1234)
}

// The payload is discarded; only success or the error's status remains.
assert_eq!(read_register().ntstatus_or_success(), STATUS_SUCCESS);

ntresult::Result	NTSTATUS
Ok(T)	STATUS_SUCCESS
Err(Error(status))	status

Returning expected non-success statuses

Some kernel APIs use non-success NTSTATUS values as valid outcomes (e.g. STATUS_BUFFER_TOO_SMALL).

Return them as Ok in a StatusResult, and they survive extraction:

use ntresult::{NtStatus, Status, StatusResult};
use windows_sys::Win32::Foundation::STATUS_BUFFER_TOO_SMALL;

fn driver_fn() -> StatusResult {
    Ok(Status::from_ntstatus(STATUS_BUFFER_TOO_SMALL))
}

// The carried status survives; it is not collapsed to STATUS_SUCCESS.
assert_eq!(driver_fn().ntstatus(), STATUS_BUFFER_TOO_SMALL);

StatusResult (= Result)	NTSTATUS
Ok(Status(status))	status
Err(Error(status))	status

Status is a newtype rather than a bare NTSTATUS because NTSTATUS is an alias for i32: without it, a Result<i32> carrying a byte count would be indistinguishable from one carrying a status code.

---

Inspecting a status

An NTSTATUS is not opaque — it packs four fields:

 31 30 | 29 | 28 | 27 ------ 16 | 15 ------- 0
  Sev  | C  | R  |   Facility   |     Code

Error and Status expose the same accessors for all of them.

use ntresult::{Error, Severity};
use windows_sys::Win32::Foundation::STATUS_ACPI_INVALID_DATA;

// STATUS_ACPI_INVALID_DATA is 0xC014000F
let err = Error::from_ntstatus(STATUS_ACPI_INVALID_DATA);

assert_eq!(err.severity(), Severity::Error);
assert_eq!(err.facility(), 0x014);
assert_eq!(err.code(), 0x000F);
assert!(err.is_error());
assert!(!err.is_customer());

Severity is ordered, so err.severity() >= Severity::Warning works.

Beware is_success(): it reports the severity field, not whether the status equals STATUS_SUCCESS. STATUS_PENDING and STATUS_TIMEOUT both have Success severity while still being errors as far as into_result() is concerned.

Customer-defined status codes

Set bit 29 to mint your own codes — Microsoft guarantees it will never define a status with that bit set, so yours can never collide. Customer values are recognisable by their leading nibble: 0x2 success, 0x6 informational, 0xA warning, 0xE error.

use ntresult::Error;

// `from_bits` takes the unsigned form, so no `as i32` cast is needed.
let mine = Error::from_bits(0xE000_0001);

assert!(mine.is_customer());
assert!(mine.is_error());
assert_eq!(mine.code(), 0x0001);

---

Error Conversion

To turn an NTSTATUS straight into an Error, use the IntoError trait.

use ntresult::IntoError;
use windows_sys::Win32::Foundation::STATUS_INVALID_PARAMETER;

fn check_len(len: usize) -> ntresult::Result<()> {
    if len == 0 {
        return Err(STATUS_INVALID_PARAMETER.into_error());
    }

    Ok(())
}

assert!(check_len(0).is_err());
assert!(check_len(1).is_ok());

Common error types

The common_error module provides conversions from common Rust errors into ntresult::Error, so a Rust-level failure can propagate through ? and be returned to the kernel as a status code. Each error maps to the NTSTATUS that best describes it:

Error type	NTSTATUS	Feature
core::num::TryFromIntError	STATUS_INTEGER_OVERFLOW	always
core::net::AddrParseError	STATUS_INVALID_ADDRESS	always
alloc::collections::TryReserveError	STATUS_INSUFFICIENT_RESOURCES	alloc
core::alloc::AllocError	STATUS_INSUFFICIENT_RESOURCES	allocator-api

More types will be added in the future.

Formatting

Error and Status both implement Display and Debug, rendering the status as 0x plus eight uppercase hexadecimal digits.

use ntresult::Error;
use windows_sys::Win32::Foundation::STATUS_ACCESS_DENIED;

let err = Error::from_ntstatus(STATUS_ACCESS_DENIED);

assert_eq!(err.to_string(), "0xC0000022");            // Display
assert_eq!(format!("{err:?}"), "Error(0xC0000022)");  // Debug

Debug matters most in unwrap() panics and assert_eq! output, where a derived implementation would print Error(-1073741790) instead.

---

Macros

Shorthands for the conversions above. Each has a _ret variant that returns immediately, which is what makes them worth having in driver code full of early exits.

Macro	Expands to
ntok!(v)	Ok(v)
nterr!(s)	Err(Error::from_ntstatus(s))
ntres!(s)	s.into_result() — Ok(()) on STATUS_SUCCESS, else Err
ntok_ret!(v)	return Ok(v)
nterr_ret!(s)	return Err(Error::from_ntstatus(s))
ntres_ret!(s)	return s.into_result()
ntbail!(s)	alias for nterr_ret!

use ntresult::{ntres, nterr_ret};
use windows_sys::Win32::Foundation::{
    NTSTATUS, STATUS_INVALID_PARAMETER, STATUS_SUCCESS,
};

// Stand-in for a kernel API returning a raw status.
fn kernel_call() -> NTSTATUS {
    STATUS_SUCCESS
}

fn init(len: usize) -> ntresult::Result<()> {
    if len == 0 {
        // return Err(Error::from_ntstatus(...)) in one step
        nterr_ret!(STATUS_INVALID_PARAMETER);
    }

    // NTSTATUS -> Result, then propagate with `?`
    ntres!(kernel_call())?;

    Ok(())
}

assert!(init(0).is_err());
assert!(init(4).is_ok());

ntok! and ntok_ret! perform no conversion — they are plain Ok(..) and return Ok(..), provided so the family reads consistently.

ntbail! is the same macro as nterr_ret! under the name used by anyhow and similar crates; pick whichever reads better where you are.

---

Minimum supported Rust version

1.85, set by the 2024 edition. The allocator-api feature additionally requires a nightly compiler; everything else builds on stable.

The MSRV is treated as a compatibility promise: raising it is a breaking change and will come with a minor version bump before 1.0.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.