Add partial support for safe shared structs via the #[safe_shared_extern] attribute - #1715
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Add partial support for safe shared structs via the #[safe_shared_extern] attribute#1715kolayne wants to merge 3 commits into
#[safe_shared_extern] attribute#1715kolayne wants to merge 3 commits into
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Rewrites the library to rely on `cxx` rather than `autocxx` as the bindings back-end. Updates the building script accordingly. Note that a custom version of cxx is used: it includes the patch dtolnay/cxx#1715 for the `#[safe_shared_extern]` attribute. Motivation for the change: wasm32 support (trymirai#8). xgrammar-rs now compiles for `wasm32-wasip1` (and, supposedly, other wasi targets), though for now it still requires the `WASI_SYSROOT` environment variable to be set to the path to [wasi-sdk](https://github.com/WebAssembly/wasi-sdk) version 33 or newer compiled with exception support (`-DWASI_SDK_EXCEPTIONS=ON`).
kolayne
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Rewrites the library to rely on `cxx` rather than `autocxx` as the bindings back-end. Updates the building script accordingly. Note that a custom version of cxx is used: it includes the patch dtolnay/cxx#1715 for the `#[safe_shared_extern]` attribute. Motivation for the change: wasm32 support (trymirai#8). xgrammar-rs now compiles for `wasm32-wasip1` (and, supposedly, other wasi targets), though for now it still requires the `WASI_SYSROOT` environment variable to be set to the path to [wasi-sdk](https://github.com/WebAssembly/wasi-sdk) version 33 or newer compiled with exception support (`-DWASI_SDK_EXCEPTIONS=ON`).
kolayne
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May 28, 2026
Rewrites the library to rely on `cxx` rather than `autocxx` as the bindings back-end. Updates the building script accordingly. Note that a custom version of cxx is used: it includes the patch dtolnay/cxx#1715 for the `#[safe_shared_extern]` attribute. Motivation for the change: wasm32 support (trymirai#8). xgrammar-rs now compiles for `wasm32-wasip1` (and, supposedly, other wasi targets), though for now it still requires the `WASI_SYSROOT` environment variable to be set to the path to [wasi-sdk](https://github.com/WebAssembly/wasi-sdk) version 33 or newer compiled with exception support (`-DWASI_SDK_EXCEPTIONS=ON`).
kolayne
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Rewrites the library to rely on `cxx` rather than `autocxx` as the bindings back-end. Updates the building script accordingly. Note that a custom version of cxx is used: it includes the patch dtolnay/cxx#1715 for the `#[safe_shared_extern]` attribute. Motivation for the change: wasm32 support (trymirai#8). xgrammar-rs now compiles for `wasm32-wasip1` (and, supposedly, other wasi targets), though for now it still requires the `WASI_SYSROOT` environment variable to be set to the path to [wasi-sdk](https://github.com/WebAssembly/wasi-sdk) version 33 or newer compiled with exception support (`-DWASI_SDK_EXCEPTIONS=ON`).
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Adds the `safe_shared_extern` attribute.
The new attribute allows to define a shared struct that is automatically
verified for compatibility with the struct defined in C++.
This only works for structs that have no padding in their layout.
This also currently requires that the C++ struct is trivial, though
this may be relaxed.
The syntax is as follows:
```rust
mod ffi {
#[safe_shared_extern]
struct S {
pub a: i32,
pub b: i32,
}
extern "C++" {
include!("include.hpp");
// Note: no need to include `type S;` (the legacy unsafe syntax)
unsafe fn f() -> S;
}
}
```
TODO: add tests
Implement tests that various declaration mismatches are detected, as well as that the positive case works.
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Adds the
safe_shared_externattribute.The new attribute allows to define a shared struct that is automatically verified for compatibility with the struct defined in C++.
This only works for structs that have no padding in their layout. This also currently requires that the C++ struct is trivial, though this requirement may be relaxed.
The syntax is as follows:
Partially addresses #871.