3339dd1f01
This commit implements the `post-return` feature of the canonical ABI in the component model. This attribute is an optionally-specified function which is to be executed after the return value has been processed by the caller to optionally clean-up the return value. This enables, for example, returning an allocated string and the host then knows how to clean it up to prevent memory leaks in the original module. The API exposed in this PR changes the prior `TypedFunc::call` API in behavior but not in its signature. Previously the `TypedFunc::call` method would set the `may_enter` flag on the way out, but now that operation is deferred until a new `TypedFunc::post_return` method is called. This means that once a method on an instance is invoked then nothing else can be done on the instance until the `post_return` method is called. Note that the method must be called irrespective of whether the `post-return` canonical ABI option was specified or not. Internally wasm will be invoked if necessary. This is a pretty wonky and unergonomic API to work with. For now I couldn't think of a better alternative that improved on the ergonomics. In the theory that the raw Wasmtime bindings for a component may not be used all that heavily (instead `wit-bindgen` would largely be used) I'm hoping that this isn't too much of an issue in the future. cc #4185
133 lines
3.6 KiB
Rust
133 lines
3.6 KiB
Rust
use anyhow::Result;
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use wasmtime::component::Component;
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use wasmtime::{Config, Engine};
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mod func;
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mod import;
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mod nested;
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mod post_return;
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// A simple bump allocator which can be used with modules
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const REALLOC_AND_FREE: &str = r#"
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(global $last (mut i32) (i32.const 8))
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(func $realloc (export "realloc")
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(param $old_ptr i32)
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(param $old_size i32)
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(param $align i32)
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(param $new_size i32)
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(result i32)
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;; Test if the old pointer is non-null
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local.get $old_ptr
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if
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;; If the old size is bigger than the new size then
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;; this is a shrink and transparently allow it
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local.get $old_size
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local.get $new_size
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i32.gt_u
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if
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local.get $old_ptr
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return
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end
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;; ... otherwise this is unimplemented
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unreachable
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end
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;; align up `$last`
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(global.set $last
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(i32.and
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(i32.add
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(global.get $last)
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(i32.add
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(local.get $align)
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(i32.const -1)))
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(i32.xor
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(i32.add
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(local.get $align)
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(i32.const -1))
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(i32.const -1))))
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;; save the current value of `$last` as the return value
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global.get $last
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;; ensure anything necessary is set to valid data by spraying a bit
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;; pattern that is invalid
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global.get $last
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i32.const 0xde
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local.get $new_size
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memory.fill
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;; bump our pointer
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(global.set $last
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(i32.add
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(global.get $last)
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(local.get $new_size)))
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)
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"#;
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fn engine() -> Engine {
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let mut config = Config::new();
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config.wasm_component_model(true);
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Engine::new(&config).unwrap()
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}
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#[test]
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fn components_importing_modules() -> Result<()> {
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let engine = engine();
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// FIXME: these components should actually get instantiated in `*.wast`
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// tests once supplying imports has actually been implemented.
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Component::new(
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&engine,
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r#"
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(component
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(import "" (core module))
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)
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"#,
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)?;
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Component::new(
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&engine,
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r#"
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(component
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(import "" (core module $m1
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(import "" "" (func))
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(import "" "x" (global i32))
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(export "a" (table 1 funcref))
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(export "b" (memory 1))
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(export "c" (func (result f32)))
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(export "d" (global i64))
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))
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(core module $m2
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(func (export ""))
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(global (export "x") i32 i32.const 0)
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)
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(core instance $i2 (instantiate (module $m2)))
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(core instance $i1 (instantiate (module $m1) (with "" (instance $i2))))
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(core module $m3
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(import "mod" "1" (memory 1))
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(import "mod" "2" (table 1 funcref))
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(import "mod" "3" (global i64))
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(import "mod" "4" (func (result f32)))
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)
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(core instance $i3 (instantiate (module $m3)
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(with "mod" (instance
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(export "1" (memory $i1 "b"))
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(export "2" (table $i1 "a"))
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(export "3" (global $i1 "d"))
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(export "4" (func $i1 "c"))
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))
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))
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)
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"#,
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)?;
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Ok(())
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}
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