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
This patch makes `NativeType` to `libffi::middle::Type` conversion
failliable and w.t disallows struct with empty fields. libffi does not
handle "empty" struct because they don't exist in C (or Rust).
Fixes #17481
Adds support for passing and returning structs as buffers to FFI. This does not implement fastapi support for structs. Needed for certain system APIs such as AppKit on macOS.
- [x] `dlfcn.rs` - `dlopen()`-related code.
- [x] `turbocall.rs` - Call trampoline JIT compiler.
- [x] `repr.rs` - Pointer representation. Home of the UnsafePointerView
ops.
- [x] `symbol.rs` - Function symbol related code.
- [x] `callback.rs` - Home of `Deno.UnsafeCallback` ops.
- [x] `ir.rs` - Intermediate representation for values. Home of the
`NativeValue` type.
- [x] `call.rs` - Generic call ops. Home to everything related to
calling FFI symbols.
- [x] `static.rs` - static symbol support
I find easier to work with this setup, I eventually want to expand
TurboCall to unroll type conversion loop in generic calls, generate code
for individual symbols (lazy function pointers), etc.
