Support calling C++ and Rust methods #121
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These methods can be declared in the bridge by naming the first argument self and making it a reference to the containing class, e.g., fn get(self: &C) -> usize; fn set(self: &mut C, n: usize); This syntax requires Rust 1.43. Note that the implementation also changes the internal naming of shim functions so that they also contain the name of the owning class, if any. This allows defining multiple methods with the same name on different objects.
These methods can be declared in the bridge by naming the first argument self and making it a reference to the containing class, e.g., fn get(self: &R) -> usize; fn set(self: &mut R, n: usize); This syntax requires Rust 1.43.
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Thanks, this is great! I'll get a chance to review the implementation tomorrow. If someone needs method support on 1.42 and isn't satisfied waiting for the 1.43 release, it would be possible for us to accept |
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This is great, I can really use this. |
gen/write.rs
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| writeln!(out, "struct {} final {{", ety.ident); | ||
| for method in methods { | ||
| write!(out, " "); | ||
| let sig = &method.sig; | ||
| let local_name = method.ident.to_string(); | ||
| write_rust_function_shim_decl(out, &local_name, sig, None, false); | ||
| writeln!(out, ";"); | ||
| } | ||
| writeln!(out, "}};"); |
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We need a private or deleted default constructor and copy constructor in here. Otherwise this allows C++ to obtain an opaque Rust type by value and call methods on it, which is unsound.
Specifically the R2 struct from tests/ffi/lib.rs currently turns into:
struct R2 final {
size_t get() noexcept;
size_t set(size_t n) noexcept;
};and this allows C++ to write R2{}.get() which becomes UB.
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Thanks for catching that!
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Thanks, this looks good to me. I'm not sure if it's marked Draft because you are still working on it but feel free to send follow-up PRs as needed.
One note: I am going to remove the changes from demo-rs and the readme, since I'd like to keep that first intro code snippet as focused as possible on the most important concepts. We'll need to figure out somewhere else to put exhaustive documentation of the full feature set (namespace is another; #86) rather than frontloading everything in that first snippet.
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I marked it as a draft because I thought we wanted to wait until Rust 1.43 was released, but it looks like you dealt with that as a follow-up. Thanks! |
This adds support for calling C++ and Rust methods with the syntax suggested in #51:
fn get_name(self: &ThingC) -> &CxxString;
fn print(self: &ThingR);
It requires Rust 1.43 to use this syntax.