nuttx: clean up module by dybucc · Pull Request #5245 · rust-lang/libc

dybucc · 2026-07-03T07:58:53Z

Description

This PR consists of an overall clean up of the NuttX module. It adds missing types, fixes one type definition, replaces equivalent with mirrored definitions (fixed-width types with "variable" C types,) and provides correct support for some build-time configuration options.

The build-time configuration options correspond with CONFIG_SMALL_MEMORY and CONFIG_FS_LARGEFILE. The former enables types with pointer bit width (size_t and ssize_t) to be narrower than required in the target. It is enabled by default in 16-bit machine word targets but can also be enabled in other targets. The latter option enables support for LFS bindings. The default under all targets is to expose 32-bit types and no suffixed 64-bit types. It is only if the above option is set that (1) suffixed types are exposed and (2) unsuffixed types are made 64-bits wide. I have decided against exposing the suffixed types because it's redundant.

Sources

NuttX source repository.
- https://github.com/search?q=repo%3Aapache%2Fnuttx+path%3Aarch%2F**%2F*+%2F%5Cb_ssize_t%5Cb%2F&type=code
- https://github.com/apache/nuttx/blob/master/include/sys/types.h

Checklist

Relevant tests in libc-test/semver have been updated
No placeholder or unstable values like *LAST or *MAX are included (see #3131)
Tested locally (cd libc-test && cargo test --target mytarget); especially relevant for platforms that may not be checked in CI

@rustbot label +stable-nominated

tgross35 · 2026-07-03T14:06:22Z

 pub type key_t = u32;
 pub type nlink_t = u16;
-pub type ino_t = u16;
+pub type ino_t = u32;


"nuttx: fix ino_t definition" this happened just last week apache/nuttx@50377d0, I have no clue what the release/support schedule looks like but we should probably hold off a bit. Or at least hear from the maintainers.

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just pinged the maintainers.

tgross35 · 2026-07-03T14:11:02Z

 pub type locale_t = *mut i8;
 pub type mode_t = u32;
 pub type nfds_t = u32;
-pub type off_t = i64;


"nuttx: provide correct lfs support": It looks like we were already supporting CONFIG_FS_LARGEFILE - why the change?

View changes since the review

we were not correctly supporting that configuration. without it enabled, all targets get 32-bit file offset types. with it enabled, they all get 64-bit file offset types.

it would likely come off as a surprise if somebody didn't have CONFIG_FS_LARGEFILE enabled but found that our types are 64-bits either way.

I mean we were only supporting CONFIG_FS_LARGEFILE, right? That's completely fine, every platform has dozens of ways you could configure it that make something break for Rust.

I mean we were only supporting CONFIG_FS_LARGEFILE, right? That's completely fine, every platform has dozens of ways you could configure it that make something break for Rust.

Yes, it is unlikely to support arbitrary configurations of the NuttX ABI on the Rust side, so we must restrict the configuration options that affect fundamental data type definitions and only support the most commonly used combinations.

tgross35 · 2026-07-03T14:13:13Z

 }

+cfg_if! {
+    if #[cfg(nuttx_small_mm)] {


"nuttx: expose cfg for small memory model" similarly, I don't think there is any need to add this - it's extra configuration complexity in libc and has no known users. This would probably have to be a separate target in rustc, anyway.

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dybucc · 2026-07-07T15:20:11Z

@no1wudi, you think we can already have an ino_t definition that matches upstream? there was a recent change there and this pr includes it, but maybe that's a bit too early to make changes.

@rustbot ready

no1wudi · 2026-07-08T00:57:24Z

+// types are themselves 64-bits wide. We choose to expose ony the latter.
+cfg_if! {
+    if #[cfg(gnu_file_offset_bits64)] {
+        pub type fsblkcnt_t = u64;


There are too many configuration options inside Nuttx; it would be better to only support specific projects. For example, FS_LARGEFS must be enabled; otherwise, compilation becomes overly difficult.

View changes since the review

done. thanks for getting back.

fix signedness of wchar_t under arm and aarch64. this was not correctly handled as this type will likely be defined in terms of predefined compiler macros [^1]. these macros expand to different types on our currently supported nuttx targets. they are only signed integers under riscv [^2]. [^1]: https://github.com/search?q=repo%3Aapache%2Fnuttx+%2F%5Cb_wchar_t%5Cb%2F&type=code [^2]: https://c.godbolt.org/z/czMY79vsh

rustbot · 2026-07-08T16:25:55Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

no1wudi · 2026-07-09T00:28:23Z

 pub type uintptr_t = usize;
 pub type ssize_t = isize;

+#[cfg(not(target_os = "nuttx"))]


Revert? https://elixir.bootlin.com/linux/v7.1.2/source/include/uapi/asm-generic/posix_types.h#L28

View changes since the review

not really, the latest commit replicates the nuttx definition ¹ more closely. if anything, the link you provide matches the current definition (a c int and not necessarily a fixed-width integer.)

Footnotes

https://github.com/apache/nuttx/blob/master/include/sys/types.h#L157 ↩

tgross35

The current form LGTM but I'll wait for maintainer ack

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rustbot added S-waiting-on-review stable-nominated This PR should be considered for cherry-pick to libc's stable release branch labels Jul 3, 2026

tgross35 reviewed Jul 3, 2026

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tgross35 added S-waiting-on-author and removed S-waiting-on-review labels Jul 4, 2026

dybucc force-pushed the nuttx-cleanup branch from 4a84e5c to 6b62a27 Compare July 7, 2026 15:19

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rustbot added S-waiting-on-review and removed S-waiting-on-author labels Jul 7, 2026

no1wudi suggested changes Jul 8, 2026

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dybucc added 2 commits July 8, 2026 18:18

nuttx: mirror type definitions

0e9c84b

dybucc force-pushed the nuttx-cleanup branch from 6b62a27 to 0e9c84b Compare July 8, 2026 16:25

no1wudi reviewed Jul 9, 2026

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tgross35 approved these changes Jul 9, 2026

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tgross35 added the S-waiting-on-maintainer label Jul 9, 2026

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dybucc commented Jul 3, 2026

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