abi-vtable-macro 0.2.0

Proc-macro generating #[repr(C)] C vtables (struct + thunks + static + getter) from Rust trait definitions, for the dyn-loader abi mode
Documentation 
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# abi-vtable-macro

`#[abi_vtable]` — annotate a Rust trait and get the complete C contract for
[dyn-loader](https://crates.io/crates/dyn-loader)'s **abi mode**:
a `#[repr(C)]` vtable struct, one `extern "C"` thunk per method, a static
vtable instance and a `#[no_mangle]` getter — all generated.

```rust
use abi_vtable_macro::abi_vtable;

#[abi_vtable(name = "calc")]
pub trait Calc {
    fn add(&self, a: i32, b: i32) -> i32;
    fn is_even(&self, x: i32) -> bool;
}

struct MyCalc;
impl Calc for MyCalc {
    fn add(&self, a: i32, b: i32) -> i32 { a + b }
    fn is_even(&self, x: i32) -> bool { x % 2 == 0 }
}

// One line: static instance + thunks + vtable + getter.
abi_vtable_impl_calc!(MyCalc, MyCalc);
```

The host (Rust, C, C++, Zig, ...) loads `calc_get_vtable` and calls through
the struct of function pointers — see dyn-loader's `AbiTable`.

## Rules

- Field order of the generated vtable **is** the protocol: it follows trait
  method declaration order. Never reorder after release.
- All fn pointers are `extern "C"` (cdecl), ctx-leading (`*mut c_void` first).
- `$instance` must be const-constructible (unit struct, `const fn`, literal).

## License

MIT