4104a674c7
Fixes denoland#16922. The error messages in the `ffi` module are somewhat cryptic when passing functions that have invalid `parameters` or `result` type strings. While the generated serializer for the `ForeignFunction` struct correctly outputs a correct and verbose message, the user sees a far less helpful `data did not match any variant` message instead. The underlying cause appears to be the fallback message in the auto-derived deserializer for untagged enums [1] generated as a result of `ForeignSymbol` being marked as `#[serde(untagged)]` [2]. Passing an unexpected value for `NativeType` causes it to error out while attempting to deserialize both enum variants -- once because it's not a match for the `ForeignStatic` variant, and once because the `ForeignFunction` deserializer rejects the invalid type for the parameters/return type. This is currently open as [serde #773](https://github.com/serde-rs/serde/issues/773), and not a trivial exercise to fix generically. [1] https://github.com/serde-rs/serde/blob/v0.9.7/serde_derive/src/de.rs#L730 [2] https://github.com/denoland/deno/blob/main/ext/ffi/dlfcn.rs#L102 [3] https://github.com/serde-rs/serde/issues/773 Note that the auto-generated deserializer for untagged enums uses a private API to buffer deserializer content that we don't have access to. Instead, we can make use of the `serde_value` crate to buffer the values. This can likely be removed once the official buffering API lands (see [4] and [5]). In addition, this crate pulls in `serde_json` as a cheap way to test that the deserializer works properly. [4] https://github.com/serde-rs/serde/issues/741 [5] https://github.com/serde-rs/serde/pull/2348 |
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|---|---|---|
| .. | ||
| 00_ffi.js | ||
| call.rs | ||
| callback.rs | ||
| Cargo.toml | ||
| dlfcn.rs | ||
| ir.rs | ||
| lib.rs | ||
| README.md | ||
| repr.rs | ||
| static.rs | ||
| symbol.rs | ||
| turbocall.rs | ||
deno_ffi
This crate implements dynamic library ffi.
Performance
Deno FFI calls have extremely low overhead (~1ns on M1 16GB RAM) and perform on par with native code. Deno leverages V8 fast api calls and JIT compiled bindings to achieve these high speeds.
Deno.dlopen generates an optimized and a fallback path. Optimized paths are
triggered when V8 decides to optimize the function, hence call through the Fast
API. Fallback paths handle types like function callbacks and implement proper
error handling for unexpected types, that is not supported in Fast calls.
Optimized calls enter a JIT compiled function "trampoline" that translates Fast
API values directly for symbol calls. JIT compilation itself is super fast,
thanks to tinycc. Currently, the optimized path is only supported on Linux and
MacOS.
To run benchmarks:
target/release/deno bench --allow-ffi --allow-read --unstable ./test_ffi/tests/bench.js