wasmtime/runtime/linker.rs
1use crate::func::HostFunc;
2use crate::hash_map::{Entry, HashMap};
3use crate::instance::InstancePre;
4use crate::store::StoreOpaque;
5use crate::{
6 AsContext, AsContextMut, Caller, Engine, Extern, ExternType, Func, FuncType, ImportType,
7 Instance, Module, StoreContextMut, Val, ValRaw,
8};
9use crate::{IntoFunc, prelude::*};
10use alloc::sync::Arc;
11use core::fmt::{self, Debug};
12#[cfg(feature = "async")]
13use core::future::Future;
14use core::marker;
15use log::warn;
16
17/// Structure used to link wasm modules/instances together.
18///
19/// This structure is used to assist in instantiating a [`Module`]. A [`Linker`]
20/// is a way of performing name resolution to make instantiating a module easier
21/// than specifying positional imports to [`Instance::new`]. [`Linker`] is a
22/// name-based resolver where names are dynamically defined and then used to
23/// instantiate a [`Module`].
24///
25/// An important method is [`Linker::instantiate`] which takes a module to
26/// instantiate into the provided store. This method will automatically select
27/// all the right imports for the [`Module`] to be instantiated, and will
28/// otherwise return an error if an import isn't satisfied.
29///
30/// ## Name Resolution
31///
32/// As mentioned previously, `Linker` is a form of name resolver. It will be
33/// using the string-based names of imports on a module to attempt to select a
34/// matching item to hook up to it. This name resolution has two-levels of
35/// namespaces, a module level and a name level. Each item is defined within a
36/// module and then has its own name. This basically follows the wasm standard
37/// for modularization.
38///
39/// Names in a `Linker` cannot be defined twice, but allowing duplicates by
40/// shadowing the previous definition can be controlled with the
41/// [`Linker::allow_shadowing`] method.
42///
43/// ## Commands and Reactors
44///
45/// The [`Linker`] type provides conveniences for working with WASI Commands and
46/// Reactors through the [`Linker::module`] method. This will automatically
47/// handle instantiation and calling `_start` and such as appropriate
48/// depending on the inferred type of module.
49///
50/// ## Type parameter `T`
51///
52/// It's worth pointing out that the type parameter `T` on [`Linker<T>`] does
53/// not represent that `T` is stored within a [`Linker`]. Rather the `T` is used
54/// to ensure that linker-defined functions and stores instantiated into all use
55/// the same matching `T` as host state.
56///
57/// ## Multiple `Store`s
58///
59/// The [`Linker`] type is designed to be compatible, in some scenarios, with
60/// instantiation in multiple [`Store`]s. Specifically host-defined functions
61/// created in [`Linker`] with [`Linker::func_new`], [`Linker::func_wrap`], and
62/// their async versions are compatible to instantiate into any [`Store`]. This
63/// enables programs which want to instantiate lots of modules to create one
64/// [`Linker`] value at program start up and use that continuously for each
65/// [`Store`] created over the lifetime of the program.
66///
67/// Note that once [`Store`]-owned items, such as [`Global`], are defined within
68/// a [`Linker`] then it is no longer compatible with any [`Store`]. At that
69/// point only the [`Store`] that owns the [`Global`] can be used to instantiate
70/// modules.
71///
72/// ## Multiple `Engine`s
73///
74/// The [`Linker`] type is not compatible with usage between multiple [`Engine`]
75/// values. An [`Engine`] is provided when a [`Linker`] is created and only
76/// stores and items which originate from that [`Engine`] can be used with this
77/// [`Linker`]. If more than one [`Engine`] is used with a [`Linker`] then that
78/// may cause a panic at runtime, similar to how if a [`Func`] is used with the
79/// wrong [`Store`] that can also panic at runtime.
80///
81/// [`Store`]: crate::Store
82/// [`Global`]: crate::Global
83pub struct Linker<T> {
84 engine: Engine,
85 string2idx: HashMap<Arc<str>, usize>,
86 strings: Vec<Arc<str>>,
87 map: HashMap<ImportKey, Definition>,
88 allow_shadowing: bool,
89 allow_unknown_exports: bool,
90 _marker: marker::PhantomData<fn() -> T>,
91}
92
93impl<T> Debug for Linker<T> {
94 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
95 f.debug_struct("Linker").finish_non_exhaustive()
96 }
97}
98
99impl<T> Clone for Linker<T> {
100 fn clone(&self) -> Linker<T> {
101 Linker {
102 engine: self.engine.clone(),
103 string2idx: self.string2idx.clone(),
104 strings: self.strings.clone(),
105 map: self.map.clone(),
106 allow_shadowing: self.allow_shadowing,
107 allow_unknown_exports: self.allow_unknown_exports,
108 _marker: self._marker,
109 }
110 }
111}
112
113#[derive(Copy, Clone, Hash, PartialEq, Eq)]
114struct ImportKey {
115 name: usize,
116 module: usize,
117}
118
119#[derive(Clone)]
120pub(crate) enum Definition {
121 Extern(Extern, DefinitionType),
122 HostFunc(Arc<HostFunc>),
123}
124
125/// This is a sort of slimmed down `ExternType` which notably doesn't have a
126/// `FuncType`, which is an allocation, and additionally retains the current
127/// size of the table/memory.
128#[derive(Clone, Debug)]
129pub(crate) enum DefinitionType {
130 Func(wasmtime_environ::VMSharedTypeIndex),
131 Global(wasmtime_environ::Global),
132 // Note that tables and memories store not only the original type
133 // information but additionally the current size of the table/memory, as
134 // this is used during linking since the min size specified in the type may
135 // no longer be the current size of the table/memory.
136 Table(wasmtime_environ::Table, u64),
137 Memory(wasmtime_environ::Memory, u64),
138 Tag(wasmtime_environ::Tag),
139}
140
141impl<T> Linker<T> {
142 /// Creates a new [`Linker`].
143 ///
144 /// The linker will define functions within the context of the `engine`
145 /// provided and can only instantiate modules for a [`Store`][crate::Store]
146 /// that is also defined within the same [`Engine`]. Usage of stores with
147 /// different [`Engine`]s may cause a panic when used with this [`Linker`].
148 pub fn new(engine: &Engine) -> Linker<T> {
149 Linker {
150 engine: engine.clone(),
151 map: HashMap::new(),
152 string2idx: HashMap::new(),
153 strings: Vec::new(),
154 allow_shadowing: false,
155 allow_unknown_exports: false,
156 _marker: marker::PhantomData,
157 }
158 }
159
160 /// Returns the [`Engine`] this is connected to.
161 pub fn engine(&self) -> &Engine {
162 &self.engine
163 }
164
165 /// Configures whether this [`Linker`] will shadow previous duplicate
166 /// definitions of the same signature.
167 ///
168 /// By default a [`Linker`] will disallow duplicate definitions of the same
169 /// signature. This method, however, can be used to instead allow duplicates
170 /// and have the latest definition take precedence when linking modules.
171 ///
172 /// # Examples
173 ///
174 /// ```
175 /// # use wasmtime::*;
176 /// # fn main() -> anyhow::Result<()> {
177 /// # let engine = Engine::default();
178 /// let mut linker = Linker::<()>::new(&engine);
179 /// linker.func_wrap("", "", || {})?;
180 ///
181 /// // by default, duplicates are disallowed
182 /// assert!(linker.func_wrap("", "", || {}).is_err());
183 ///
184 /// // but shadowing can be configured to be allowed as well
185 /// linker.allow_shadowing(true);
186 /// linker.func_wrap("", "", || {})?;
187 /// # Ok(())
188 /// # }
189 /// ```
190 pub fn allow_shadowing(&mut self, allow: bool) -> &mut Self {
191 self.allow_shadowing = allow;
192 self
193 }
194
195 /// Configures whether this [`Linker`] will allow unknown exports from
196 /// command modules.
197 ///
198 /// By default a [`Linker`] will error when unknown exports are encountered
199 /// in a command module while using [`Linker::module`].
200 ///
201 /// This method can be used to allow unknown exports from command modules.
202 ///
203 /// # Examples
204 ///
205 /// ```
206 /// # use wasmtime::*;
207 /// # fn main() -> anyhow::Result<()> {
208 /// # let engine = Engine::default();
209 /// # let module = Module::new(&engine, "(module)")?;
210 /// # let mut store = Store::new(&engine, ());
211 /// let mut linker = Linker::new(&engine);
212 /// linker.allow_unknown_exports(true);
213 /// linker.module(&mut store, "mod", &module)?;
214 /// # Ok(())
215 /// # }
216 /// ```
217 pub fn allow_unknown_exports(&mut self, allow: bool) -> &mut Self {
218 self.allow_unknown_exports = allow;
219 self
220 }
221
222 /// Implement any imports of the given [`Module`] with a function which traps.
223 ///
224 /// By default a [`Linker`] will error when unknown imports are encountered
225 /// in a command module while using [`Linker::module`].
226 ///
227 /// This method can be used to allow unknown imports from command modules.
228 ///
229 /// # Examples
230 ///
231 /// ```
232 /// # use wasmtime::*;
233 /// # fn main() -> anyhow::Result<()> {
234 /// # let engine = Engine::default();
235 /// # let module = Module::new(&engine, "(module (import \"unknown\" \"import\" (func)))")?;
236 /// # let mut store = Store::new(&engine, ());
237 /// let mut linker = Linker::new(&engine);
238 /// linker.define_unknown_imports_as_traps(&module)?;
239 /// linker.instantiate(&mut store, &module)?;
240 /// # Ok(())
241 /// # }
242 /// ```
243 pub fn define_unknown_imports_as_traps(&mut self, module: &Module) -> anyhow::Result<()>
244 where
245 T: 'static,
246 {
247 for import in module.imports() {
248 if let Err(import_err) = self._get_by_import(&import) {
249 if let ExternType::Func(func_ty) = import_err.ty() {
250 self.func_new(import.module(), import.name(), func_ty, move |_, _, _| {
251 bail!(import_err.clone());
252 })?;
253 }
254 }
255 }
256 Ok(())
257 }
258
259 /// Implement any function imports of the [`Module`] with a function that
260 /// ignores its arguments and returns default values.
261 ///
262 /// Default values are either zero or null, depending on the value type.
263 ///
264 /// This method can be used to allow unknown imports from command modules.
265 ///
266 /// # Example
267 ///
268 /// ```
269 /// # use wasmtime::*;
270 /// # fn main() -> anyhow::Result<()> {
271 /// # let engine = Engine::default();
272 /// # let module = Module::new(&engine, "(module (import \"unknown\" \"import\" (func)))")?;
273 /// # let mut store = Store::new(&engine, ());
274 /// let mut linker = Linker::new(&engine);
275 /// linker.define_unknown_imports_as_default_values(&mut store, &module)?;
276 /// linker.instantiate(&mut store, &module)?;
277 /// # Ok(())
278 /// # }
279 /// ```
280 pub fn define_unknown_imports_as_default_values(
281 &mut self,
282 store: &mut impl AsContextMut<Data = T>,
283 module: &Module,
284 ) -> anyhow::Result<()>
285 where
286 T: 'static,
287 {
288 for import in module.imports() {
289 if let Err(import_err) = self._get_by_import(&import) {
290 let default_extern =
291 import_err
292 .ty()
293 .default_value(&mut *store)
294 .with_context(|| {
295 anyhow!(
296 "no default value exists for `{}::{}` with type `{:?}`",
297 import.module(),
298 import.name(),
299 import_err.ty(),
300 )
301 })?;
302 self.define(
303 store.as_context(),
304 import.module(),
305 import.name(),
306 default_extern,
307 )?;
308 }
309 }
310 Ok(())
311 }
312
313 /// Defines a new item in this [`Linker`].
314 ///
315 /// This method will add a new definition, by name, to this instance of
316 /// [`Linker`]. The `module` and `name` provided are what to name the
317 /// `item`.
318 ///
319 /// # Errors
320 ///
321 /// Returns an error if the `module` and `name` already identify an item
322 /// of the same type as the `item` provided and if shadowing is disallowed.
323 /// For more information see the documentation on [`Linker`].
324 ///
325 /// # Examples
326 ///
327 /// ```
328 /// # use wasmtime::*;
329 /// # fn main() -> anyhow::Result<()> {
330 /// # let engine = Engine::default();
331 /// # let mut store = Store::new(&engine, ());
332 /// let mut linker = Linker::new(&engine);
333 /// let ty = GlobalType::new(ValType::I32, Mutability::Const);
334 /// let global = Global::new(&mut store, ty, Val::I32(0x1234))?;
335 /// linker.define(&store, "host", "offset", global)?;
336 ///
337 /// let wat = r#"
338 /// (module
339 /// (import "host" "offset" (global i32))
340 /// (memory 1)
341 /// (data (global.get 0) "foo")
342 /// )
343 /// "#;
344 /// let module = Module::new(&engine, wat)?;
345 /// linker.instantiate(&mut store, &module)?;
346 /// # Ok(())
347 /// # }
348 /// ```
349 pub fn define(
350 &mut self,
351 store: impl AsContext<Data = T>,
352 module: &str,
353 name: &str,
354 item: impl Into<Extern>,
355 ) -> Result<&mut Self>
356 where
357 T: 'static,
358 {
359 let store = store.as_context();
360 let key = self.import_key(module, Some(name));
361 self.insert(key, Definition::new(store.0, item.into()))?;
362 Ok(self)
363 }
364
365 /// Same as [`Linker::define`], except only the name of the import is
366 /// provided, not a module name as well.
367 ///
368 /// This is only relevant when working with the module linking proposal
369 /// where one-level names are allowed (in addition to two-level names).
370 /// Otherwise this method need not be used.
371 pub fn define_name(
372 &mut self,
373 store: impl AsContext<Data = T>,
374 name: &str,
375 item: impl Into<Extern>,
376 ) -> Result<&mut Self>
377 where
378 T: 'static,
379 {
380 let store = store.as_context();
381 let key = self.import_key(name, None);
382 self.insert(key, Definition::new(store.0, item.into()))?;
383 Ok(self)
384 }
385
386 /// Creates a [`Func::new`]-style function named in this linker.
387 ///
388 /// For more information see [`Linker::func_wrap`].
389 ///
390 /// # Panics
391 ///
392 /// Panics if the given function type is not associated with the same engine
393 /// as this linker.
394 pub fn func_new(
395 &mut self,
396 module: &str,
397 name: &str,
398 ty: FuncType,
399 func: impl Fn(Caller<'_, T>, &[Val], &mut [Val]) -> Result<()> + Send + Sync + 'static,
400 ) -> Result<&mut Self>
401 where
402 T: 'static,
403 {
404 assert!(ty.comes_from_same_engine(self.engine()));
405 let func = HostFunc::new(&self.engine, ty, func);
406 let key = self.import_key(module, Some(name));
407 self.insert(key, Definition::HostFunc(Arc::new(func)))?;
408 Ok(self)
409 }
410
411 /// Creates a [`Func::new_unchecked`]-style function named in this linker.
412 ///
413 /// For more information see [`Linker::func_wrap`].
414 ///
415 /// # Panics
416 ///
417 /// Panics if the given function type is not associated with the same engine
418 /// as this linker.
419 pub unsafe fn func_new_unchecked(
420 &mut self,
421 module: &str,
422 name: &str,
423 ty: FuncType,
424 func: impl Fn(Caller<'_, T>, &mut [ValRaw]) -> Result<()> + Send + Sync + 'static,
425 ) -> Result<&mut Self>
426 where
427 T: 'static,
428 {
429 assert!(ty.comes_from_same_engine(self.engine()));
430 let func = HostFunc::new_unchecked(&self.engine, ty, func);
431 let key = self.import_key(module, Some(name));
432 self.insert(key, Definition::HostFunc(Arc::new(func)))?;
433 Ok(self)
434 }
435
436 /// Creates a [`Func::new_async`]-style function named in this linker.
437 ///
438 /// For more information see [`Linker::func_wrap`].
439 ///
440 /// # Panics
441 ///
442 /// This method panics in the following situations:
443 ///
444 /// * This linker is not associated with an [async
445 /// config](crate::Config::async_support).
446 ///
447 /// * If the given function type is not associated with the same engine as
448 /// this linker.
449 #[cfg(all(feature = "async", feature = "cranelift"))]
450 pub fn func_new_async<F>(
451 &mut self,
452 module: &str,
453 name: &str,
454 ty: FuncType,
455 func: F,
456 ) -> Result<&mut Self>
457 where
458 F: for<'a> Fn(
459 Caller<'a, T>,
460 &'a [Val],
461 &'a mut [Val],
462 ) -> Box<dyn Future<Output = Result<()>> + Send + 'a>
463 + Send
464 + Sync
465 + 'static,
466 T: 'static,
467 {
468 assert!(
469 self.engine.config().async_support,
470 "cannot use `func_new_async` without enabling async support in the config"
471 );
472 assert!(ty.comes_from_same_engine(self.engine()));
473 self.func_new(module, name, ty, move |caller, params, results| {
474 let instance = caller.caller();
475 caller.store.with_blocking(|store, cx| {
476 let caller = Caller::new(store, instance);
477 cx.block_on(core::pin::Pin::from(func(caller, params, results)))
478 })?
479 })
480 }
481
482 /// Define a host function within this linker.
483 ///
484 /// For information about how the host function operates, see
485 /// [`Func::wrap`]. That includes information about translating Rust types
486 /// to WebAssembly native types.
487 ///
488 /// This method creates a host-provided function in this linker under the
489 /// provided name. This method is distinct in its capability to create a
490 /// [`Store`](crate::Store)-independent function. This means that the
491 /// function defined here can be used to instantiate instances in multiple
492 /// different stores, or in other words the function can be loaded into
493 /// different stores.
494 ///
495 /// Note that the capability mentioned here applies to all other
496 /// host-function-defining-methods on [`Linker`] as well. All of them can be
497 /// used to create instances of [`Func`] within multiple stores. In a
498 /// multithreaded program, for example, this means that the host functions
499 /// could be called concurrently if different stores are executing on
500 /// different threads.
501 ///
502 /// # Errors
503 ///
504 /// Returns an error if the `module` and `name` already identify an item
505 /// of the same type as the `item` provided and if shadowing is disallowed.
506 /// For more information see the documentation on [`Linker`].
507 ///
508 /// # Examples
509 ///
510 /// ```
511 /// # use wasmtime::*;
512 /// # fn main() -> anyhow::Result<()> {
513 /// # let engine = Engine::default();
514 /// let mut linker = Linker::new(&engine);
515 /// linker.func_wrap("host", "double", |x: i32| x * 2)?;
516 /// linker.func_wrap("host", "log_i32", |x: i32| println!("{}", x))?;
517 /// linker.func_wrap("host", "log_str", |caller: Caller<'_, ()>, ptr: i32, len: i32| {
518 /// // ...
519 /// })?;
520 ///
521 /// let wat = r#"
522 /// (module
523 /// (import "host" "double" (func (param i32) (result i32)))
524 /// (import "host" "log_i32" (func (param i32)))
525 /// (import "host" "log_str" (func (param i32 i32)))
526 /// )
527 /// "#;
528 /// let module = Module::new(&engine, wat)?;
529 ///
530 /// // instantiate in multiple different stores
531 /// for _ in 0..10 {
532 /// let mut store = Store::new(&engine, ());
533 /// linker.instantiate(&mut store, &module)?;
534 /// }
535 /// # Ok(())
536 /// # }
537 /// ```
538 pub fn func_wrap<Params, Args>(
539 &mut self,
540 module: &str,
541 name: &str,
542 func: impl IntoFunc<T, Params, Args>,
543 ) -> Result<&mut Self>
544 where
545 T: 'static,
546 {
547 let func = HostFunc::wrap(&self.engine, func);
548 let key = self.import_key(module, Some(name));
549 self.insert(key, Definition::HostFunc(Arc::new(func)))?;
550 Ok(self)
551 }
552
553 /// Asynchronous analog of [`Linker::func_wrap`].
554 #[cfg(feature = "async")]
555 pub fn func_wrap_async<F, Params: crate::WasmTyList, Args: crate::WasmRet>(
556 &mut self,
557 module: &str,
558 name: &str,
559 func: F,
560 ) -> Result<&mut Self>
561 where
562 F: for<'a> Fn(Caller<'a, T>, Params) -> Box<dyn Future<Output = Args> + Send + 'a>
563 + Send
564 + Sync
565 + 'static,
566 T: 'static,
567 {
568 assert!(
569 self.engine.config().async_support,
570 "cannot use `func_wrap_async` without enabling async support on the config",
571 );
572 let func =
573 HostFunc::wrap_inner(&self.engine, move |caller: Caller<'_, T>, args: Params| {
574 let instance = caller.caller();
575 let result = caller.store.block_on(|store| {
576 let caller = Caller::new(store, instance);
577 func(caller, args).into()
578 });
579 match result {
580 Ok(ret) => ret.into_fallible(),
581 Err(e) => Args::fallible_from_error(e),
582 }
583 });
584 let key = self.import_key(module, Some(name));
585 self.insert(key, Definition::HostFunc(Arc::new(func)))?;
586 Ok(self)
587 }
588
589 /// Convenience wrapper to define an entire [`Instance`] in this linker.
590 ///
591 /// This function is a convenience wrapper around [`Linker::define`] which
592 /// will define all exports on `instance` into this linker. The module name
593 /// for each export is `module_name`, and the name for each export is the
594 /// name in the instance itself.
595 ///
596 /// Note that when this API is used the [`Linker`] is no longer compatible
597 /// with multi-[`Store`][crate::Store] instantiation because the items
598 /// defined within this store will belong to the `store` provided, and only
599 /// the `store` provided.
600 ///
601 /// # Errors
602 ///
603 /// Returns an error if the any item is redefined twice in this linker (for
604 /// example the same `module_name` was already defined) and shadowing is
605 /// disallowed, or if `instance` comes from a different
606 /// [`Store`](crate::Store) than this [`Linker`] originally was created
607 /// with.
608 ///
609 /// # Panics
610 ///
611 /// Panics if `instance` does not belong to `store`.
612 ///
613 /// # Examples
614 ///
615 /// ```
616 /// # use wasmtime::*;
617 /// # fn main() -> anyhow::Result<()> {
618 /// # let engine = Engine::default();
619 /// # let mut store = Store::new(&engine, ());
620 /// let mut linker = Linker::new(&engine);
621 ///
622 /// // Instantiate a small instance...
623 /// let wat = r#"(module (func (export "run") ))"#;
624 /// let module = Module::new(&engine, wat)?;
625 /// let instance = linker.instantiate(&mut store, &module)?;
626 ///
627 /// // ... and inform the linker that the name of this instance is
628 /// // `instance1`. This defines the `instance1::run` name for our next
629 /// // module to use.
630 /// linker.instance(&mut store, "instance1", instance)?;
631 ///
632 /// let wat = r#"
633 /// (module
634 /// (import "instance1" "run" (func $instance1_run))
635 /// (func (export "run")
636 /// call $instance1_run
637 /// )
638 /// )
639 /// "#;
640 /// let module = Module::new(&engine, wat)?;
641 /// let instance = linker.instantiate(&mut store, &module)?;
642 /// # Ok(())
643 /// # }
644 /// ```
645 pub fn instance(
646 &mut self,
647 mut store: impl AsContextMut<Data = T>,
648 module_name: &str,
649 instance: Instance,
650 ) -> Result<&mut Self>
651 where
652 T: 'static,
653 {
654 let mut store = store.as_context_mut();
655 let exports = instance
656 .exports(&mut store)
657 .map(|e| {
658 (
659 self.import_key(module_name, Some(e.name())),
660 e.into_extern(),
661 )
662 })
663 .collect::<Vec<_>>();
664 for (key, export) in exports {
665 self.insert(key, Definition::new(store.0, export))?;
666 }
667 Ok(self)
668 }
669
670 /// Define automatic instantiations of a [`Module`] in this linker.
671 ///
672 /// This automatically handles [Commands and Reactors] instantiation and
673 /// initialization.
674 ///
675 /// Exported functions of a Command module may be called directly, however
676 /// instead of having a single instance which is reused for each call,
677 /// each call creates a new instance, which lives for the duration of the
678 /// call. The imports of the Command are resolved once, and reused for
679 /// each instantiation, so all dependencies need to be present at the time
680 /// when `Linker::module` is called.
681 ///
682 /// For Reactors, a single instance is created, and an initialization
683 /// function is called, and then its exports may be called.
684 ///
685 /// Ordinary modules which don't declare themselves to be either Commands
686 /// or Reactors are treated as Reactors without any initialization calls.
687 ///
688 /// [Commands and Reactors]: https://github.com/WebAssembly/WASI/blob/main/legacy/application-abi.md#current-unstable-abi
689 ///
690 /// # Errors
691 ///
692 /// Returns an error if the any item is redefined twice in this linker (for
693 /// example the same `module_name` was already defined) and shadowing is
694 /// disallowed, if `instance` comes from a different
695 /// [`Store`](crate::Store) than this [`Linker`] originally was created
696 /// with, or if a Reactor initialization function traps.
697 ///
698 /// # Panics
699 ///
700 /// Panics if any item used to instantiate the provided [`Module`] is not
701 /// owned by `store`, or if the `store` provided comes from a different
702 /// [`Engine`] than this [`Linker`].
703 ///
704 /// # Examples
705 ///
706 /// ```
707 /// # use wasmtime::*;
708 /// # fn main() -> anyhow::Result<()> {
709 /// # let engine = Engine::default();
710 /// # let mut store = Store::new(&engine, ());
711 /// let mut linker = Linker::new(&engine);
712 ///
713 /// // Instantiate a small instance and inform the linker that the name of
714 /// // this instance is `instance1`. This defines the `instance1::run` name
715 /// // for our next module to use.
716 /// let wat = r#"(module (func (export "run") ))"#;
717 /// let module = Module::new(&engine, wat)?;
718 /// linker.module(&mut store, "instance1", &module)?;
719 ///
720 /// let wat = r#"
721 /// (module
722 /// (import "instance1" "run" (func $instance1_run))
723 /// (func (export "run")
724 /// call $instance1_run
725 /// )
726 /// )
727 /// "#;
728 /// let module = Module::new(&engine, wat)?;
729 /// let instance = linker.instantiate(&mut store, &module)?;
730 /// # Ok(())
731 /// # }
732 /// ```
733 ///
734 /// For a Command, a new instance is created for each call.
735 ///
736 /// ```
737 /// # use wasmtime::*;
738 /// # fn main() -> anyhow::Result<()> {
739 /// # let engine = Engine::default();
740 /// # let mut store = Store::new(&engine, ());
741 /// let mut linker = Linker::new(&engine);
742 ///
743 /// // Create a Command that attempts to count the number of times it is run, but is
744 /// // foiled by each call getting a new instance.
745 /// let wat = r#"
746 /// (module
747 /// (global $counter (mut i32) (i32.const 0))
748 /// (func (export "_start")
749 /// (global.set $counter (i32.add (global.get $counter) (i32.const 1)))
750 /// )
751 /// (func (export "read_counter") (result i32)
752 /// (global.get $counter)
753 /// )
754 /// )
755 /// "#;
756 /// let module = Module::new(&engine, wat)?;
757 /// linker.module(&mut store, "commander", &module)?;
758 /// let run = linker.get_default(&mut store, "")?
759 /// .typed::<(), ()>(&store)?
760 /// .clone();
761 /// run.call(&mut store, ())?;
762 /// run.call(&mut store, ())?;
763 /// run.call(&mut store, ())?;
764 ///
765 /// let wat = r#"
766 /// (module
767 /// (import "commander" "_start" (func $commander_start))
768 /// (import "commander" "read_counter" (func $commander_read_counter (result i32)))
769 /// (func (export "run") (result i32)
770 /// call $commander_start
771 /// call $commander_start
772 /// call $commander_start
773 /// call $commander_read_counter
774 /// )
775 /// )
776 /// "#;
777 /// let module = Module::new(&engine, wat)?;
778 /// linker.module(&mut store, "", &module)?;
779 /// let run = linker.get(&mut store, "", "run").unwrap().into_func().unwrap();
780 /// let count = run.typed::<(), i32>(&store)?.call(&mut store, ())?;
781 /// assert_eq!(count, 0, "a Command should get a fresh instance on each invocation");
782 ///
783 /// # Ok(())
784 /// # }
785 /// ```
786 pub fn module(
787 &mut self,
788 mut store: impl AsContextMut<Data = T>,
789 module_name: &str,
790 module: &Module,
791 ) -> Result<&mut Self>
792 where
793 T: 'static,
794 {
795 // NB: this is intended to function the same as `Linker::module_async`,
796 // they should be kept in sync.
797
798 // This assert isn't strictly necessary since it'll bottom out in the
799 // `HostFunc::to_func` method anyway. This is placed earlier for this
800 // function though to prevent the functions created here from delaying
801 // the panic until they're called.
802 assert!(
803 Engine::same(&self.engine, store.as_context().engine()),
804 "different engines for this linker and the store provided"
805 );
806 match ModuleKind::categorize(module)? {
807 ModuleKind::Command => {
808 self.command(
809 store,
810 module_name,
811 module,
812 |store, func_ty, export_name, instance_pre| {
813 Func::new(
814 store,
815 func_ty.clone(),
816 move |mut caller, params, results| {
817 // Create a new instance for this command execution.
818 let instance = instance_pre.instantiate(&mut caller)?;
819
820 // `unwrap()` everything here because we know the instance contains a
821 // function export with the given name and signature because we're
822 // iterating over the module it was instantiated from.
823 instance
824 .get_export(&mut caller, &export_name)
825 .unwrap()
826 .into_func()
827 .unwrap()
828 .call(&mut caller, params, results)?;
829
830 Ok(())
831 },
832 )
833 },
834 )
835 }
836 ModuleKind::Reactor => {
837 let instance = self.instantiate(&mut store, &module)?;
838
839 if let Some(export) = instance.get_export(&mut store, "_initialize") {
840 if let Extern::Func(func) = export {
841 func.typed::<(), ()>(&store)
842 .and_then(|f| f.call(&mut store, ()))
843 .context("calling the Reactor initialization function")?;
844 }
845 }
846
847 self.instance(store, module_name, instance)
848 }
849 }
850 }
851
852 /// Define automatic instantiations of a [`Module`] in this linker.
853 ///
854 /// This is the same as [`Linker::module`], except for async `Store`s.
855 #[cfg(all(feature = "async", feature = "cranelift"))]
856 pub async fn module_async(
857 &mut self,
858 mut store: impl AsContextMut<Data = T>,
859 module_name: &str,
860 module: &Module,
861 ) -> Result<&mut Self>
862 where
863 T: Send + 'static,
864 {
865 // NB: this is intended to function the same as `Linker::module`, they
866 // should be kept in sync.
867 assert!(
868 Engine::same(&self.engine, store.as_context().engine()),
869 "different engines for this linker and the store provided"
870 );
871 match ModuleKind::categorize(module)? {
872 ModuleKind::Command => self.command(
873 store,
874 module_name,
875 module,
876 |store, func_ty, export_name, instance_pre| {
877 let upvars = Arc::new((instance_pre, export_name));
878 Func::new_async(
879 store,
880 func_ty.clone(),
881 move |mut caller, params, results| {
882 let upvars = upvars.clone();
883 Box::new(async move {
884 let (instance_pre, export_name) = &*upvars;
885 let instance = instance_pre.instantiate_async(&mut caller).await?;
886
887 instance
888 .get_export(&mut caller, &export_name)
889 .unwrap()
890 .into_func()
891 .unwrap()
892 .call_async(&mut caller, params, results)
893 .await?;
894 Ok(())
895 })
896 },
897 )
898 },
899 ),
900 ModuleKind::Reactor => {
901 let instance = self.instantiate_async(&mut store, &module).await?;
902
903 if let Some(export) = instance.get_export(&mut store, "_initialize") {
904 if let Extern::Func(func) = export {
905 let func = func
906 .typed::<(), ()>(&store)
907 .context("loading the Reactor initialization function")?;
908 func.call_async(&mut store, ())
909 .await
910 .context("calling the Reactor initialization function")?;
911 }
912 }
913
914 self.instance(store, module_name, instance)
915 }
916 }
917 }
918
919 fn command(
920 &mut self,
921 mut store: impl AsContextMut<Data = T>,
922 module_name: &str,
923 module: &Module,
924 mk_func: impl Fn(&mut StoreContextMut<T>, &FuncType, String, InstancePre<T>) -> Func,
925 ) -> Result<&mut Self>
926 where
927 T: 'static,
928 {
929 let mut store = store.as_context_mut();
930 for export in module.exports() {
931 if let Some(func_ty) = export.ty().func() {
932 let instance_pre = self.instantiate_pre(module)?;
933 let export_name = export.name().to_owned();
934 let func = mk_func(&mut store, func_ty, export_name, instance_pre);
935 let key = self.import_key(module_name, Some(export.name()));
936 self.insert(key, Definition::new(store.0, func.into()))?;
937 } else if export.name() == "memory" && export.ty().memory().is_some() {
938 // Allow an exported "memory" memory for now.
939 } else if export.name() == "__indirect_function_table" && export.ty().table().is_some()
940 {
941 // Allow an exported "__indirect_function_table" table for now.
942 } else if export.name() == "table" && export.ty().table().is_some() {
943 // Allow an exported "table" table for now.
944 } else if export.name() == "__data_end" && export.ty().global().is_some() {
945 // Allow an exported "__data_end" memory for compatibility with toolchains
946 // which use --export-dynamic, which unfortunately doesn't work the way
947 // we want it to.
948 warn!("command module exporting '__data_end' is deprecated");
949 } else if export.name() == "__heap_base" && export.ty().global().is_some() {
950 // Allow an exported "__data_end" memory for compatibility with toolchains
951 // which use --export-dynamic, which unfortunately doesn't work the way
952 // we want it to.
953 warn!("command module exporting '__heap_base' is deprecated");
954 } else if export.name() == "__dso_handle" && export.ty().global().is_some() {
955 // Allow an exported "__dso_handle" memory for compatibility with toolchains
956 // which use --export-dynamic, which unfortunately doesn't work the way
957 // we want it to.
958 warn!("command module exporting '__dso_handle' is deprecated")
959 } else if export.name() == "__rtti_base" && export.ty().global().is_some() {
960 // Allow an exported "__rtti_base" memory for compatibility with
961 // AssemblyScript.
962 warn!(
963 "command module exporting '__rtti_base' is deprecated; pass `--runtime half` to the AssemblyScript compiler"
964 );
965 } else if !self.allow_unknown_exports {
966 bail!("command export '{}' is not a function", export.name());
967 }
968 }
969
970 Ok(self)
971 }
972
973 /// Aliases one item's name as another.
974 ///
975 /// This method will alias an item with the specified `module` and `name`
976 /// under a new name of `as_module` and `as_name`.
977 ///
978 /// # Errors
979 ///
980 /// Returns an error if any shadowing violations happen while defining new
981 /// items, or if the original item wasn't defined.
982 pub fn alias(
983 &mut self,
984 module: &str,
985 name: &str,
986 as_module: &str,
987 as_name: &str,
988 ) -> Result<&mut Self> {
989 let src = self.import_key(module, Some(name));
990 let dst = self.import_key(as_module, Some(as_name));
991 match self.map.get(&src).cloned() {
992 Some(item) => self.insert(dst, item)?,
993 None => bail!("no item named `{}::{}` defined", module, name),
994 }
995 Ok(self)
996 }
997
998 /// Aliases one module's name as another.
999 ///
1000 /// This method will alias all currently defined under `module` to also be
1001 /// defined under the name `as_module` too.
1002 ///
1003 /// # Errors
1004 ///
1005 /// Returns an error if any shadowing violations happen while defining new
1006 /// items.
1007 pub fn alias_module(&mut self, module: &str, as_module: &str) -> Result<()> {
1008 let module = self.intern_str(module);
1009 let as_module = self.intern_str(as_module);
1010 let items = self
1011 .map
1012 .iter()
1013 .filter(|(key, _def)| key.module == module)
1014 .map(|(key, def)| (key.name, def.clone()))
1015 .collect::<Vec<_>>();
1016 for (name, item) in items {
1017 self.insert(
1018 ImportKey {
1019 module: as_module,
1020 name,
1021 },
1022 item,
1023 )?;
1024 }
1025 Ok(())
1026 }
1027
1028 fn insert(&mut self, key: ImportKey, item: Definition) -> Result<()> {
1029 match self.map.entry(key) {
1030 Entry::Occupied(_) if !self.allow_shadowing => {
1031 let module = &self.strings[key.module];
1032 let desc = match self.strings.get(key.name) {
1033 Some(name) => format!("{module}::{name}"),
1034 None => module.to_string(),
1035 };
1036 bail!("import of `{}` defined twice", desc)
1037 }
1038 Entry::Occupied(mut o) => {
1039 o.insert(item);
1040 }
1041 Entry::Vacant(v) => {
1042 v.insert(item);
1043 }
1044 }
1045 Ok(())
1046 }
1047
1048 fn import_key(&mut self, module: &str, name: Option<&str>) -> ImportKey {
1049 ImportKey {
1050 module: self.intern_str(module),
1051 name: name
1052 .map(|name| self.intern_str(name))
1053 .unwrap_or(usize::max_value()),
1054 }
1055 }
1056
1057 fn intern_str(&mut self, string: &str) -> usize {
1058 if let Some(idx) = self.string2idx.get(string) {
1059 return *idx;
1060 }
1061 let string: Arc<str> = string.into();
1062 let idx = self.strings.len();
1063 self.strings.push(string.clone());
1064 self.string2idx.insert(string, idx);
1065 idx
1066 }
1067
1068 /// Attempts to instantiate the `module` provided.
1069 ///
1070 /// This method will attempt to assemble a list of imports that correspond
1071 /// to the imports required by the [`Module`] provided. This list
1072 /// of imports is then passed to [`Instance::new`] to continue the
1073 /// instantiation process.
1074 ///
1075 /// Each import of `module` will be looked up in this [`Linker`] and must
1076 /// have previously been defined. If it was previously defined with an
1077 /// incorrect signature or if it was not previously defined then an error
1078 /// will be returned because the import can not be satisfied.
1079 ///
1080 /// Per the WebAssembly spec, instantiation includes running the module's
1081 /// start function, if it has one (not to be confused with the `_start`
1082 /// function, which is not run).
1083 ///
1084 /// # Errors
1085 ///
1086 /// This method can fail because an import may not be found, or because
1087 /// instantiation itself may fail. For information on instantiation
1088 /// failures see [`Instance::new`]. If an import is not found, the error
1089 /// may be downcast to an [`UnknownImportError`].
1090 ///
1091 ///
1092 /// # Panics
1093 ///
1094 /// Panics if any item used to instantiate `module` is not owned by
1095 /// `store`. Additionally this will panic if the [`Engine`] that the `store`
1096 /// belongs to is different than this [`Linker`].
1097 ///
1098 /// # Examples
1099 ///
1100 /// ```
1101 /// # use wasmtime::*;
1102 /// # fn main() -> anyhow::Result<()> {
1103 /// # let engine = Engine::default();
1104 /// # let mut store = Store::new(&engine, ());
1105 /// let mut linker = Linker::new(&engine);
1106 /// linker.func_wrap("host", "double", |x: i32| x * 2)?;
1107 ///
1108 /// let wat = r#"
1109 /// (module
1110 /// (import "host" "double" (func (param i32) (result i32)))
1111 /// )
1112 /// "#;
1113 /// let module = Module::new(&engine, wat)?;
1114 /// linker.instantiate(&mut store, &module)?;
1115 /// # Ok(())
1116 /// # }
1117 /// ```
1118 pub fn instantiate(
1119 &self,
1120 mut store: impl AsContextMut<Data = T>,
1121 module: &Module,
1122 ) -> Result<Instance>
1123 where
1124 T: 'static,
1125 {
1126 self._instantiate_pre(module, Some(store.as_context_mut().0))?
1127 .instantiate(store)
1128 }
1129
1130 /// Attempts to instantiate the `module` provided. This is the same as
1131 /// [`Linker::instantiate`], except for async `Store`s.
1132 #[cfg(feature = "async")]
1133 pub async fn instantiate_async(
1134 &self,
1135 mut store: impl AsContextMut<Data = T>,
1136 module: &Module,
1137 ) -> Result<Instance>
1138 where
1139 T: Send + 'static,
1140 {
1141 self._instantiate_pre(module, Some(store.as_context_mut().0))?
1142 .instantiate_async(store)
1143 .await
1144 }
1145
1146 /// Performs all checks necessary for instantiating `module` with this
1147 /// linker, except that instantiation doesn't actually finish.
1148 ///
1149 /// This method is used for front-loading type-checking information as well
1150 /// as collecting the imports to use to instantiate a module with. The
1151 /// returned [`InstancePre`] represents a ready-to-be-instantiated module,
1152 /// which can also be instantiated multiple times if desired.
1153 ///
1154 /// # Errors
1155 ///
1156 /// Returns an error which may be downcast to an [`UnknownImportError`] if
1157 /// the module has any unresolvable imports.
1158 ///
1159 /// # Examples
1160 ///
1161 /// ```
1162 /// # use wasmtime::*;
1163 /// # fn main() -> anyhow::Result<()> {
1164 /// # let engine = Engine::default();
1165 /// # let mut store = Store::new(&engine, ());
1166 /// let mut linker = Linker::new(&engine);
1167 /// linker.func_wrap("host", "double", |x: i32| x * 2)?;
1168 ///
1169 /// let wat = r#"
1170 /// (module
1171 /// (import "host" "double" (func (param i32) (result i32)))
1172 /// )
1173 /// "#;
1174 /// let module = Module::new(&engine, wat)?;
1175 /// let instance_pre = linker.instantiate_pre(&module)?;
1176 ///
1177 /// // Finish instantiation after the type-checking has all completed...
1178 /// let instance = instance_pre.instantiate(&mut store)?;
1179 ///
1180 /// // ... and we can even continue to keep instantiating if desired!
1181 /// instance_pre.instantiate(&mut store)?;
1182 /// instance_pre.instantiate(&mut store)?;
1183 ///
1184 /// // Note that functions defined in a linker with `func_wrap` and similar
1185 /// // constructors are not owned by any particular `Store`, so we can also
1186 /// // instantiate our `instance_pre` in other stores because no imports
1187 /// // belong to the original store.
1188 /// let mut new_store = Store::new(&engine, ());
1189 /// instance_pre.instantiate(&mut new_store)?;
1190 /// # Ok(())
1191 /// # }
1192 /// ```
1193 pub fn instantiate_pre(&self, module: &Module) -> Result<InstancePre<T>>
1194 where
1195 T: 'static,
1196 {
1197 self._instantiate_pre(module, None)
1198 }
1199
1200 /// This is split out to optionally take a `store` so that when the
1201 /// `.instantiate` API is used we can get fresh up-to-date type information
1202 /// for memories and their current size, if necessary.
1203 ///
1204 /// Note that providing a `store` here is not required for correctness
1205 /// per-se. If one is not provided, such as the with the `instantiate_pre`
1206 /// API, then the type information used for memories and tables will reflect
1207 /// their size when inserted into the linker rather than their current size.
1208 /// This isn't expected to be much of a problem though since
1209 /// per-store-`Linker` types are likely using `.instantiate(..)` and
1210 /// per-`Engine` linkers don't have memories/tables in them.
1211 fn _instantiate_pre(
1212 &self,
1213 module: &Module,
1214 store: Option<&StoreOpaque>,
1215 ) -> Result<InstancePre<T>>
1216 where
1217 T: 'static,
1218 {
1219 let mut imports = module
1220 .imports()
1221 .map(|import| self._get_by_import(&import))
1222 .collect::<Result<Vec<_>, _>>()?;
1223 if let Some(store) = store {
1224 for import in imports.iter_mut() {
1225 import.update_size(store);
1226 }
1227 }
1228 unsafe { InstancePre::new(module, imports) }
1229 }
1230
1231 /// Returns an iterator over all items defined in this `Linker`, in
1232 /// arbitrary order.
1233 ///
1234 /// The iterator returned will yield 3-tuples where the first two elements
1235 /// are the module name and item name for the external item, and the third
1236 /// item is the item itself that is defined.
1237 ///
1238 /// Note that multiple `Extern` items may be defined for the same
1239 /// module/name pair.
1240 ///
1241 /// # Panics
1242 ///
1243 /// This function will panic if the `store` provided does not come from the
1244 /// same [`Engine`] that this linker was created with.
1245 pub fn iter<'a: 'p, 'p>(
1246 &'a self,
1247 mut store: impl AsContextMut<Data = T> + 'p,
1248 ) -> impl Iterator<Item = (&'a str, &'a str, Extern)> + 'p
1249 where
1250 T: 'static,
1251 {
1252 self.map.iter().map(move |(key, item)| {
1253 let store = store.as_context_mut();
1254 (
1255 &*self.strings[key.module],
1256 &*self.strings[key.name],
1257 // Should be safe since `T` is connecting the linker and store
1258 unsafe { item.to_extern(store.0) },
1259 )
1260 })
1261 }
1262
1263 /// Looks up a previously defined value in this [`Linker`], identified by
1264 /// the names provided.
1265 ///
1266 /// Returns `None` if this name was not previously defined in this
1267 /// [`Linker`].
1268 ///
1269 /// # Panics
1270 ///
1271 /// This function will panic if the `store` provided does not come from the
1272 /// same [`Engine`] that this linker was created with.
1273 pub fn get(
1274 &self,
1275 mut store: impl AsContextMut<Data = T>,
1276 module: &str,
1277 name: &str,
1278 ) -> Option<Extern>
1279 where
1280 T: 'static,
1281 {
1282 let store = store.as_context_mut().0;
1283 // Should be safe since `T` is connecting the linker and store
1284 Some(unsafe { self._get(module, name)?.to_extern(store) })
1285 }
1286
1287 fn _get(&self, module: &str, name: &str) -> Option<&Definition> {
1288 let key = ImportKey {
1289 module: *self.string2idx.get(module)?,
1290 name: *self.string2idx.get(name)?,
1291 };
1292 self.map.get(&key)
1293 }
1294
1295 /// Looks up a value in this `Linker` which matches the `import` type
1296 /// provided.
1297 ///
1298 /// Returns `None` if no match was found.
1299 ///
1300 /// # Panics
1301 ///
1302 /// This function will panic if the `store` provided does not come from the
1303 /// same [`Engine`] that this linker was created with.
1304 pub fn get_by_import(
1305 &self,
1306 mut store: impl AsContextMut<Data = T>,
1307 import: &ImportType,
1308 ) -> Option<Extern>
1309 where
1310 T: 'static,
1311 {
1312 let store = store.as_context_mut().0;
1313 // Should be safe since `T` is connecting the linker and store
1314 Some(unsafe { self._get_by_import(import).ok()?.to_extern(store) })
1315 }
1316
1317 fn _get_by_import(&self, import: &ImportType) -> Result<Definition, UnknownImportError> {
1318 match self._get(import.module(), import.name()) {
1319 Some(item) => Ok(item.clone()),
1320 None => Err(UnknownImportError::new(import)),
1321 }
1322 }
1323
1324 /// Returns the "default export" of a module.
1325 ///
1326 /// An export with an empty string is considered to be a "default export".
1327 /// "_start" is also recognized for compatibility.
1328 ///
1329 /// # Panics
1330 ///
1331 /// Panics if the default function found is not owned by `store`. This
1332 /// function will also panic if the `store` provided does not come from the
1333 /// same [`Engine`] that this linker was created with.
1334 pub fn get_default(&self, mut store: impl AsContextMut<Data = T>, module: &str) -> Result<Func>
1335 where
1336 T: 'static,
1337 {
1338 if let Some(external) = self.get(&mut store, module, "") {
1339 if let Extern::Func(func) = external {
1340 return Ok(func);
1341 }
1342 bail!("default export in '{}' is not a function", module);
1343 }
1344
1345 // For compatibility, also recognize "_start".
1346 if let Some(external) = self.get(&mut store, module, "_start") {
1347 if let Extern::Func(func) = external {
1348 return Ok(func);
1349 }
1350 bail!("`_start` in '{}' is not a function", module);
1351 }
1352
1353 // Otherwise return a no-op function.
1354 Ok(Func::wrap(store, || {}))
1355 }
1356}
1357
1358impl<T: 'static> Default for Linker<T> {
1359 fn default() -> Linker<T> {
1360 Linker::new(&Engine::default())
1361 }
1362}
1363
1364impl Definition {
1365 fn new(store: &StoreOpaque, item: Extern) -> Definition {
1366 let ty = DefinitionType::from(store, &item);
1367 Definition::Extern(item, ty)
1368 }
1369
1370 pub(crate) fn ty(&self) -> DefinitionType {
1371 match self {
1372 Definition::Extern(_, ty) => ty.clone(),
1373 Definition::HostFunc(func) => DefinitionType::Func(func.sig_index()),
1374 }
1375 }
1376
1377 /// Note the unsafety here is due to calling `HostFunc::to_func`. The
1378 /// requirement here is that the `T` that was originally used to create the
1379 /// `HostFunc` matches the `T` on the store.
1380 pub(crate) unsafe fn to_extern(&self, store: &mut StoreOpaque) -> Extern {
1381 match self {
1382 Definition::Extern(e, _) => e.clone(),
1383 Definition::HostFunc(func) => func.to_func(store).into(),
1384 }
1385 }
1386
1387 pub(crate) fn comes_from_same_store(&self, store: &StoreOpaque) -> bool {
1388 match self {
1389 Definition::Extern(e, _) => e.comes_from_same_store(store),
1390 Definition::HostFunc(_func) => true,
1391 }
1392 }
1393
1394 fn update_size(&mut self, store: &StoreOpaque) {
1395 match self {
1396 Definition::Extern(Extern::Memory(m), DefinitionType::Memory(_, size)) => {
1397 *size = m.internal_size(store);
1398 }
1399 Definition::Extern(Extern::SharedMemory(m), DefinitionType::Memory(_, size)) => {
1400 *size = m.size();
1401 }
1402 Definition::Extern(Extern::Table(m), DefinitionType::Table(_, size)) => {
1403 *size = m.internal_size(store);
1404 }
1405 _ => {}
1406 }
1407 }
1408}
1409
1410impl DefinitionType {
1411 pub(crate) fn from(store: &StoreOpaque, item: &Extern) -> DefinitionType {
1412 match item {
1413 Extern::Func(f) => DefinitionType::Func(f.type_index(store)),
1414 Extern::Table(t) => {
1415 DefinitionType::Table(*t.wasmtime_ty(store), t.internal_size(store))
1416 }
1417 Extern::Global(t) => DefinitionType::Global(*t.wasmtime_ty(store)),
1418 Extern::Memory(t) => {
1419 DefinitionType::Memory(*t.wasmtime_ty(store), t.internal_size(store))
1420 }
1421 Extern::SharedMemory(t) => DefinitionType::Memory(*t.ty().wasmtime_memory(), t.size()),
1422 Extern::Tag(t) => DefinitionType::Tag(*t.wasmtime_ty(store)),
1423 }
1424 }
1425
1426 pub(crate) fn desc(&self) -> &'static str {
1427 match self {
1428 DefinitionType::Func(_) => "function",
1429 DefinitionType::Table(..) => "table",
1430 DefinitionType::Memory(..) => "memory",
1431 DefinitionType::Global(_) => "global",
1432 DefinitionType::Tag(_) => "tag",
1433 }
1434 }
1435}
1436
1437/// Modules can be interpreted either as Commands or Reactors.
1438enum ModuleKind {
1439 /// The instance is a Command, meaning an instance is created for each
1440 /// exported function and lives for the duration of the function call.
1441 Command,
1442
1443 /// The instance is a Reactor, meaning one instance is created which
1444 /// may live across multiple calls.
1445 Reactor,
1446}
1447
1448impl ModuleKind {
1449 /// Determine whether the given module is a Command or a Reactor.
1450 fn categorize(module: &Module) -> Result<ModuleKind> {
1451 let command_start = module.get_export("_start");
1452 let reactor_start = module.get_export("_initialize");
1453 match (command_start, reactor_start) {
1454 (Some(command_start), None) => {
1455 if let Some(_) = command_start.func() {
1456 Ok(ModuleKind::Command)
1457 } else {
1458 bail!("`_start` must be a function")
1459 }
1460 }
1461 (None, Some(reactor_start)) => {
1462 if let Some(_) = reactor_start.func() {
1463 Ok(ModuleKind::Reactor)
1464 } else {
1465 bail!("`_initialize` must be a function")
1466 }
1467 }
1468 (None, None) => {
1469 // Module declares neither of the recognized functions, so treat
1470 // it as a reactor with no initialization function.
1471 Ok(ModuleKind::Reactor)
1472 }
1473 (Some(_), Some(_)) => {
1474 // Module declares itself to be both a Command and a Reactor.
1475 bail!("Program cannot be both a Command and a Reactor")
1476 }
1477 }
1478 }
1479}
1480
1481/// Error for an unresolvable import.
1482///
1483/// Returned - wrapped in an [`anyhow::Error`] - by [`Linker::instantiate`] and
1484/// related methods for modules with unresolvable imports.
1485#[derive(Clone, Debug)]
1486pub struct UnknownImportError {
1487 module: String,
1488 name: String,
1489 ty: ExternType,
1490}
1491
1492impl UnknownImportError {
1493 fn new(import: &ImportType) -> Self {
1494 Self {
1495 module: import.module().to_string(),
1496 name: import.name().to_string(),
1497 ty: import.ty(),
1498 }
1499 }
1500
1501 /// Returns the module name that the unknown import was expected to come from.
1502 pub fn module(&self) -> &str {
1503 &self.module
1504 }
1505
1506 /// Returns the field name of the module that the unknown import was expected to come from.
1507 pub fn name(&self) -> &str {
1508 &self.name
1509 }
1510
1511 /// Returns the type of the unknown import.
1512 pub fn ty(&self) -> ExternType {
1513 self.ty.clone()
1514 }
1515}
1516
1517impl fmt::Display for UnknownImportError {
1518 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1519 write!(
1520 f,
1521 "unknown import: `{}::{}` has not been defined",
1522 self.module, self.name,
1523 )
1524 }
1525}
1526
1527impl core::error::Error for UnknownImportError {}