| commit | e2e12f853d3b318b44795b6a2b45f925e71bce54 | [log] [tgz] |
|---|---|---|
| author | Pierre-Clément Tosi <ptosi@google.com> | Thu Jan 25 17:59:54 2024 +0000 |
| committer | Pierre-Clément Tosi <ptosi@google.com> | Wed Feb 07 18:35:49 2024 +0000 |
| tree | 5fbd5ddd8774ca28a9cc56a7d1fb7d518207542c | |
| parent | 69cdbdb960e3a869213c773eb16ceb8af72eca38 [diff] |
Bring back upstream support for no_std in Android As the upstream crate was designed to be no_std (therefore uses core) and as the Soong targets need to build a dylib (which requires std), the crate source was being patched to remove the no_std crate attribute. In turn, as the crate doesn't define a Rust edition, Cargo (and therefore cargo_embargo) defaults to 2015, which requires explicitly importing the core crate in no-no_std environments so the code was further patched to use std modules in place of the corresponding core modules. Instead, patch the Cargo.toml to use Rust 2018 (which implicitly imports core, even in no-no_std) and wrap the no_std in a AOSP-only cfg that we enable when building Soong targets that include dylib variants. Enable that cfg from the Android.bp & cargo_embargo.json. Bug: 324074084 Test: external_updater/updater.sh update --force rust/crates/memoffset Test: cargo_embargo generate cargo_embargo.json Test: m libmemoffset libintrusive_collections Change-Id: Id76df918c0ec89651c4b84402967570e52ae1058
- Android.bp[diff]
- Cargo.toml[diff]
- cargo_embargo.json[diff]
- patches/std.diff[diff]
- src/lib.rs[diff]
- src/span_of.rs[diff]
- .github/
- patches/
- src/
- .cargo_vcs_info.json
- .gitignore
- Android.bp
- build.rs
- Cargo.toml
- Cargo.toml.orig
- cargo_embargo.json
- LICENSE
- METADATA
- MODULE_LICENSE_MIT
- OWNERS
- README.md
- TEST_MAPPING
memoffset
C-Like offset_of functionality for Rust structs.
Introduces the following macros:
offset_of!for obtaining the offset of a member of a struct.offset_of_tuple!for obtaining the offset of a member of a tuple. (Requires Rust 1.20+)offset_of_union!for obtaining the offset of a member of a union.span_of!for obtaining the range that a field, or fields, span.
memoffset works under no_std environments.
Usage
Add the following dependency to your Cargo.toml:
[dependencies] memoffset = "0.8"
These versions will compile fine with rustc versions greater or equal to 1.19.
Examples
use memoffset::{offset_of, span_of}; #[repr(C, packed)] struct Foo { a: u32, b: u32, c: [u8; 5], d: u32, } fn main() { assert_eq!(offset_of!(Foo, b), 4); assert_eq!(offset_of!(Foo, d), 4+4+5); assert_eq!(span_of!(Foo, a), 0..4); assert_eq!(span_of!(Foo, a .. c), 0..8); assert_eq!(span_of!(Foo, a ..= c), 0..13); assert_eq!(span_of!(Foo, ..= d), 0..17); assert_eq!(span_of!(Foo, b ..), 4..17); }
Usage in constants
memoffset has support for compile-time offset_of! on rust>=1.65, or on older nightly compilers.
Usage on stable Rust
Constant evaluation is automatically enabled and avilable on stable compilers starting with rustc 1.65.
This is an incomplete implementation with one caveat: Due to dependence on #![feature(const_refs_to_cell)], you cannot get the offset of a Cell field in a const-context.
This means that if need to get the offset of a cell, you'll have to remain on nightly for now.
Usage on recent nightlies
If you're using a new-enough nightly and you require the ability to get the offset of a Cell, you'll have to enable the unstable_const cargo feature, as well as enabling const_refs_to_cell in your crate root.
Do note that unstable_const is an unstable feature that is set to be removed in a future version of memoffset.
Cargo.toml:
[dependencies.memoffset] version = "0.8" features = ["unstable_const"]
Your crate root: (lib.rs/main.rs)
#![feature(const_refs_to_cell)]
Usage on older nightlies
In order to use it on an older nightly compiler, you must enable the unstable_const crate feature and several compiler features.
Your crate root: (lib.rs/main.rs)
#![feature(const_ptr_offset_from, const_refs_to_cell)]