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 ///
420 /// # Safety
421 ///
422 /// See [`Func::new_unchecked`] for more safety information.
423 pub unsafe fn func_new_unchecked(
424 &mut self,
425 module: &str,
426 name: &str,
427 ty: FuncType,
428 func: impl Fn(Caller<'_, T>, &mut [ValRaw]) -> Result<()> + Send + Sync + 'static,
429 ) -> Result<&mut Self>
430 where
431 T: 'static,
432 {
433 assert!(ty.comes_from_same_engine(self.engine()));
434 // SAFETY: the contract of this function is the same as `new_unchecked`.
435 let func = unsafe { HostFunc::new_unchecked(&self.engine, ty, func) };
436 let key = self.import_key(module, Some(name));
437 self.insert(key, Definition::HostFunc(Arc::new(func)))?;
438 Ok(self)
439 }
440
441 /// Creates a [`Func::new_async`]-style function named in this linker.
442 ///
443 /// For more information see [`Linker::func_wrap`].
444 ///
445 /// # Panics
446 ///
447 /// This method panics in the following situations:
448 ///
449 /// * This linker is not associated with an [async
450 /// config](crate::Config::async_support).
451 ///
452 /// * If the given function type is not associated with the same engine as
453 /// this linker.
454 #[cfg(all(feature = "async", feature = "cranelift"))]
455 pub fn func_new_async<F>(
456 &mut self,
457 module: &str,
458 name: &str,
459 ty: FuncType,
460 func: F,
461 ) -> Result<&mut Self>
462 where
463 F: for<'a> Fn(
464 Caller<'a, T>,
465 &'a [Val],
466 &'a mut [Val],
467 ) -> Box<dyn Future<Output = Result<()>> + Send + 'a>
468 + Send
469 + Sync
470 + 'static,
471 T: 'static,
472 {
473 assert!(
474 self.engine.config().async_support,
475 "cannot use `func_new_async` without enabling async support in the config"
476 );
477 assert!(ty.comes_from_same_engine(self.engine()));
478 self.func_new(module, name, ty, move |caller, params, results| {
479 let instance = caller.caller();
480 caller.store.with_blocking(|store, cx| {
481 let caller = Caller::new(store, instance);
482 cx.block_on(core::pin::Pin::from(func(caller, params, results)))
483 })?
484 })
485 }
486
487 /// Define a host function within this linker.
488 ///
489 /// For information about how the host function operates, see
490 /// [`Func::wrap`]. That includes information about translating Rust types
491 /// to WebAssembly native types.
492 ///
493 /// This method creates a host-provided function in this linker under the
494 /// provided name. This method is distinct in its capability to create a
495 /// [`Store`](crate::Store)-independent function. This means that the
496 /// function defined here can be used to instantiate instances in multiple
497 /// different stores, or in other words the function can be loaded into
498 /// different stores.
499 ///
500 /// Note that the capability mentioned here applies to all other
501 /// host-function-defining-methods on [`Linker`] as well. All of them can be
502 /// used to create instances of [`Func`] within multiple stores. In a
503 /// multithreaded program, for example, this means that the host functions
504 /// could be called concurrently if different stores are executing on
505 /// different threads.
506 ///
507 /// # Errors
508 ///
509 /// Returns an error if the `module` and `name` already identify an item
510 /// of the same type as the `item` provided and if shadowing is disallowed.
511 /// For more information see the documentation on [`Linker`].
512 ///
513 /// # Examples
514 ///
515 /// ```
516 /// # use wasmtime::*;
517 /// # fn main() -> anyhow::Result<()> {
518 /// # let engine = Engine::default();
519 /// let mut linker = Linker::new(&engine);
520 /// linker.func_wrap("host", "double", |x: i32| x * 2)?;
521 /// linker.func_wrap("host", "log_i32", |x: i32| println!("{}", x))?;
522 /// linker.func_wrap("host", "log_str", |caller: Caller<'_, ()>, ptr: i32, len: i32| {
523 /// // ...
524 /// })?;
525 ///
526 /// let wat = r#"
527 /// (module
528 /// (import "host" "double" (func (param i32) (result i32)))
529 /// (import "host" "log_i32" (func (param i32)))
530 /// (import "host" "log_str" (func (param i32 i32)))
531 /// )
532 /// "#;
533 /// let module = Module::new(&engine, wat)?;
534 ///
535 /// // instantiate in multiple different stores
536 /// for _ in 0..10 {
537 /// let mut store = Store::new(&engine, ());
538 /// linker.instantiate(&mut store, &module)?;
539 /// }
540 /// # Ok(())
541 /// # }
542 /// ```
543 pub fn func_wrap<Params, Args>(
544 &mut self,
545 module: &str,
546 name: &str,
547 func: impl IntoFunc<T, Params, Args>,
548 ) -> Result<&mut Self>
549 where
550 T: 'static,
551 {
552 let func = HostFunc::wrap(&self.engine, func);
553 let key = self.import_key(module, Some(name));
554 self.insert(key, Definition::HostFunc(Arc::new(func)))?;
555 Ok(self)
556 }
557
558 /// Asynchronous analog of [`Linker::func_wrap`].
559 #[cfg(feature = "async")]
560 pub fn func_wrap_async<F, Params: crate::WasmTyList, Args: crate::WasmRet>(
561 &mut self,
562 module: &str,
563 name: &str,
564 func: F,
565 ) -> Result<&mut Self>
566 where
567 F: for<'a> Fn(Caller<'a, T>, Params) -> Box<dyn Future<Output = Args> + Send + 'a>
568 + Send
569 + Sync
570 + 'static,
571 T: 'static,
572 {
573 assert!(
574 self.engine.config().async_support,
575 "cannot use `func_wrap_async` without enabling async support on the config",
576 );
577 let func =
578 HostFunc::wrap_inner(&self.engine, move |caller: Caller<'_, T>, args: Params| {
579 let instance = caller.caller();
580 let result = caller.store.block_on(|store| {
581 let caller = Caller::new(store, instance);
582 func(caller, args).into()
583 });
584 match result {
585 Ok(ret) => ret.into_fallible(),
586 Err(e) => Args::fallible_from_error(e),
587 }
588 });
589 let key = self.import_key(module, Some(name));
590 self.insert(key, Definition::HostFunc(Arc::new(func)))?;
591 Ok(self)
592 }
593
594 /// Convenience wrapper to define an entire [`Instance`] in this linker.
595 ///
596 /// This function is a convenience wrapper around [`Linker::define`] which
597 /// will define all exports on `instance` into this linker. The module name
598 /// for each export is `module_name`, and the name for each export is the
599 /// name in the instance itself.
600 ///
601 /// Note that when this API is used the [`Linker`] is no longer compatible
602 /// with multi-[`Store`][crate::Store] instantiation because the items
603 /// defined within this store will belong to the `store` provided, and only
604 /// the `store` provided.
605 ///
606 /// # Errors
607 ///
608 /// Returns an error if the any item is redefined twice in this linker (for
609 /// example the same `module_name` was already defined) and shadowing is
610 /// disallowed, or if `instance` comes from a different
611 /// [`Store`](crate::Store) than this [`Linker`] originally was created
612 /// with.
613 ///
614 /// # Panics
615 ///
616 /// Panics if `instance` does not belong to `store`.
617 ///
618 /// # Examples
619 ///
620 /// ```
621 /// # use wasmtime::*;
622 /// # fn main() -> anyhow::Result<()> {
623 /// # let engine = Engine::default();
624 /// # let mut store = Store::new(&engine, ());
625 /// let mut linker = Linker::new(&engine);
626 ///
627 /// // Instantiate a small instance...
628 /// let wat = r#"(module (func (export "run") ))"#;
629 /// let module = Module::new(&engine, wat)?;
630 /// let instance = linker.instantiate(&mut store, &module)?;
631 ///
632 /// // ... and inform the linker that the name of this instance is
633 /// // `instance1`. This defines the `instance1::run` name for our next
634 /// // module to use.
635 /// linker.instance(&mut store, "instance1", instance)?;
636 ///
637 /// let wat = r#"
638 /// (module
639 /// (import "instance1" "run" (func $instance1_run))
640 /// (func (export "run")
641 /// call $instance1_run
642 /// )
643 /// )
644 /// "#;
645 /// let module = Module::new(&engine, wat)?;
646 /// let instance = linker.instantiate(&mut store, &module)?;
647 /// # Ok(())
648 /// # }
649 /// ```
650 pub fn instance(
651 &mut self,
652 mut store: impl AsContextMut<Data = T>,
653 module_name: &str,
654 instance: Instance,
655 ) -> Result<&mut Self>
656 where
657 T: 'static,
658 {
659 let mut store = store.as_context_mut();
660 let exports = instance
661 .exports(&mut store)
662 .map(|e| {
663 (
664 self.import_key(module_name, Some(e.name())),
665 e.into_extern(),
666 )
667 })
668 .collect::<Vec<_>>();
669 for (key, export) in exports {
670 self.insert(key, Definition::new(store.0, export))?;
671 }
672 Ok(self)
673 }
674
675 /// Define automatic instantiations of a [`Module`] in this linker.
676 ///
677 /// This automatically handles [Commands and Reactors] instantiation and
678 /// initialization.
679 ///
680 /// Exported functions of a Command module may be called directly, however
681 /// instead of having a single instance which is reused for each call,
682 /// each call creates a new instance, which lives for the duration of the
683 /// call. The imports of the Command are resolved once, and reused for
684 /// each instantiation, so all dependencies need to be present at the time
685 /// when `Linker::module` is called.
686 ///
687 /// For Reactors, a single instance is created, and an initialization
688 /// function is called, and then its exports may be called.
689 ///
690 /// Ordinary modules which don't declare themselves to be either Commands
691 /// or Reactors are treated as Reactors without any initialization calls.
692 ///
693 /// [Commands and Reactors]: https://github.com/WebAssembly/WASI/blob/main/legacy/application-abi.md#current-unstable-abi
694 ///
695 /// # Errors
696 ///
697 /// Returns an error if the any item is redefined twice in this linker (for
698 /// example the same `module_name` was already defined) and shadowing is
699 /// disallowed, if `instance` comes from a different
700 /// [`Store`](crate::Store) than this [`Linker`] originally was created
701 /// with, or if a Reactor initialization function traps.
702 ///
703 /// # Panics
704 ///
705 /// Panics if any item used to instantiate the provided [`Module`] is not
706 /// owned by `store`, or if the `store` provided comes from a different
707 /// [`Engine`] than this [`Linker`].
708 ///
709 /// # Examples
710 ///
711 /// ```
712 /// # use wasmtime::*;
713 /// # fn main() -> anyhow::Result<()> {
714 /// # let engine = Engine::default();
715 /// # let mut store = Store::new(&engine, ());
716 /// let mut linker = Linker::new(&engine);
717 ///
718 /// // Instantiate a small instance and inform the linker that the name of
719 /// // this instance is `instance1`. This defines the `instance1::run` name
720 /// // for our next module to use.
721 /// let wat = r#"(module (func (export "run") ))"#;
722 /// let module = Module::new(&engine, wat)?;
723 /// linker.module(&mut store, "instance1", &module)?;
724 ///
725 /// let wat = r#"
726 /// (module
727 /// (import "instance1" "run" (func $instance1_run))
728 /// (func (export "run")
729 /// call $instance1_run
730 /// )
731 /// )
732 /// "#;
733 /// let module = Module::new(&engine, wat)?;
734 /// let instance = linker.instantiate(&mut store, &module)?;
735 /// # Ok(())
736 /// # }
737 /// ```
738 ///
739 /// For a Command, a new instance is created for each call.
740 ///
741 /// ```
742 /// # use wasmtime::*;
743 /// # fn main() -> anyhow::Result<()> {
744 /// # let engine = Engine::default();
745 /// # let mut store = Store::new(&engine, ());
746 /// let mut linker = Linker::new(&engine);
747 ///
748 /// // Create a Command that attempts to count the number of times it is run, but is
749 /// // foiled by each call getting a new instance.
750 /// let wat = r#"
751 /// (module
752 /// (global $counter (mut i32) (i32.const 0))
753 /// (func (export "_start")
754 /// (global.set $counter (i32.add (global.get $counter) (i32.const 1)))
755 /// )
756 /// (func (export "read_counter") (result i32)
757 /// (global.get $counter)
758 /// )
759 /// )
760 /// "#;
761 /// let module = Module::new(&engine, wat)?;
762 /// linker.module(&mut store, "commander", &module)?;
763 /// let run = linker.get_default(&mut store, "")?
764 /// .typed::<(), ()>(&store)?
765 /// .clone();
766 /// run.call(&mut store, ())?;
767 /// run.call(&mut store, ())?;
768 /// run.call(&mut store, ())?;
769 ///
770 /// let wat = r#"
771 /// (module
772 /// (import "commander" "_start" (func $commander_start))
773 /// (import "commander" "read_counter" (func $commander_read_counter (result i32)))
774 /// (func (export "run") (result i32)
775 /// call $commander_start
776 /// call $commander_start
777 /// call $commander_start
778 /// call $commander_read_counter
779 /// )
780 /// )
781 /// "#;
782 /// let module = Module::new(&engine, wat)?;
783 /// linker.module(&mut store, "", &module)?;
784 /// let run = linker.get(&mut store, "", "run").unwrap().into_func().unwrap();
785 /// let count = run.typed::<(), i32>(&store)?.call(&mut store, ())?;
786 /// assert_eq!(count, 0, "a Command should get a fresh instance on each invocation");
787 ///
788 /// # Ok(())
789 /// # }
790 /// ```
791 pub fn module(
792 &mut self,
793 mut store: impl AsContextMut<Data = T>,
794 module_name: &str,
795 module: &Module,
796 ) -> Result<&mut Self>
797 where
798 T: 'static,
799 {
800 // NB: this is intended to function the same as `Linker::module_async`,
801 // they should be kept in sync.
802
803 // This assert isn't strictly necessary since it'll bottom out in the
804 // `HostFunc::to_func` method anyway. This is placed earlier for this
805 // function though to prevent the functions created here from delaying
806 // the panic until they're called.
807 assert!(
808 Engine::same(&self.engine, store.as_context().engine()),
809 "different engines for this linker and the store provided"
810 );
811 match ModuleKind::categorize(module)? {
812 ModuleKind::Command => {
813 self.command(
814 store,
815 module_name,
816 module,
817 |store, func_ty, export_name, instance_pre| {
818 Func::new(
819 store,
820 func_ty.clone(),
821 move |mut caller, params, results| {
822 // Create a new instance for this command execution.
823 let instance = instance_pre.instantiate(&mut caller)?;
824
825 // `unwrap()` everything here because we know the instance contains a
826 // function export with the given name and signature because we're
827 // iterating over the module it was instantiated from.
828 instance
829 .get_export(&mut caller, &export_name)
830 .unwrap()
831 .into_func()
832 .unwrap()
833 .call(&mut caller, params, results)?;
834
835 Ok(())
836 },
837 )
838 },
839 )
840 }
841 ModuleKind::Reactor => {
842 let instance = self.instantiate(&mut store, &module)?;
843
844 if let Some(export) = instance.get_export(&mut store, "_initialize") {
845 if let Extern::Func(func) = export {
846 func.typed::<(), ()>(&store)
847 .and_then(|f| f.call(&mut store, ()))
848 .context("calling the Reactor initialization function")?;
849 }
850 }
851
852 self.instance(store, module_name, instance)
853 }
854 }
855 }
856
857 /// Define automatic instantiations of a [`Module`] in this linker.
858 ///
859 /// This is the same as [`Linker::module`], except for async `Store`s.
860 #[cfg(all(feature = "async", feature = "cranelift"))]
861 pub async fn module_async(
862 &mut self,
863 mut store: impl AsContextMut<Data = T>,
864 module_name: &str,
865 module: &Module,
866 ) -> Result<&mut Self>
867 where
868 T: Send + 'static,
869 {
870 // NB: this is intended to function the same as `Linker::module`, they
871 // should be kept in sync.
872 assert!(
873 Engine::same(&self.engine, store.as_context().engine()),
874 "different engines for this linker and the store provided"
875 );
876 match ModuleKind::categorize(module)? {
877 ModuleKind::Command => self.command(
878 store,
879 module_name,
880 module,
881 |store, func_ty, export_name, instance_pre| {
882 let upvars = Arc::new((instance_pre, export_name));
883 Func::new_async(
884 store,
885 func_ty.clone(),
886 move |mut caller, params, results| {
887 let upvars = upvars.clone();
888 Box::new(async move {
889 let (instance_pre, export_name) = &*upvars;
890 let instance = instance_pre.instantiate_async(&mut caller).await?;
891
892 instance
893 .get_export(&mut caller, &export_name)
894 .unwrap()
895 .into_func()
896 .unwrap()
897 .call_async(&mut caller, params, results)
898 .await?;
899 Ok(())
900 })
901 },
902 )
903 },
904 ),
905 ModuleKind::Reactor => {
906 let instance = self.instantiate_async(&mut store, &module).await?;
907
908 if let Some(export) = instance.get_export(&mut store, "_initialize") {
909 if let Extern::Func(func) = export {
910 let func = func
911 .typed::<(), ()>(&store)
912 .context("loading the Reactor initialization function")?;
913 func.call_async(&mut store, ())
914 .await
915 .context("calling the Reactor initialization function")?;
916 }
917 }
918
919 self.instance(store, module_name, instance)
920 }
921 }
922 }
923
924 fn command(
925 &mut self,
926 mut store: impl AsContextMut<Data = T>,
927 module_name: &str,
928 module: &Module,
929 mk_func: impl Fn(&mut StoreContextMut<T>, &FuncType, String, InstancePre<T>) -> Func,
930 ) -> Result<&mut Self>
931 where
932 T: 'static,
933 {
934 let mut store = store.as_context_mut();
935 for export in module.exports() {
936 if let Some(func_ty) = export.ty().func() {
937 let instance_pre = self.instantiate_pre(module)?;
938 let export_name = export.name().to_owned();
939 let func = mk_func(&mut store, func_ty, export_name, instance_pre);
940 let key = self.import_key(module_name, Some(export.name()));
941 self.insert(key, Definition::new(store.0, func.into()))?;
942 } else if export.name() == "memory" && export.ty().memory().is_some() {
943 // Allow an exported "memory" memory for now.
944 } else if export.name() == "__indirect_function_table" && export.ty().table().is_some()
945 {
946 // Allow an exported "__indirect_function_table" table for now.
947 } else if export.name() == "table" && export.ty().table().is_some() {
948 // Allow an exported "table" table for now.
949 } else if export.name() == "__data_end" && 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 '__data_end' is deprecated");
954 } else if export.name() == "__heap_base" && export.ty().global().is_some() {
955 // Allow an exported "__data_end" 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 '__heap_base' is deprecated");
959 } else if export.name() == "__dso_handle" && export.ty().global().is_some() {
960 // Allow an exported "__dso_handle" memory for compatibility with toolchains
961 // which use --export-dynamic, which unfortunately doesn't work the way
962 // we want it to.
963 warn!("command module exporting '__dso_handle' is deprecated")
964 } else if export.name() == "__rtti_base" && export.ty().global().is_some() {
965 // Allow an exported "__rtti_base" memory for compatibility with
966 // AssemblyScript.
967 warn!(
968 "command module exporting '__rtti_base' is deprecated; pass `--runtime half` to the AssemblyScript compiler"
969 );
970 } else if !self.allow_unknown_exports {
971 bail!("command export '{}' is not a function", export.name());
972 }
973 }
974
975 Ok(self)
976 }
977
978 /// Aliases one item's name as another.
979 ///
980 /// This method will alias an item with the specified `module` and `name`
981 /// under a new name of `as_module` and `as_name`.
982 ///
983 /// # Errors
984 ///
985 /// Returns an error if any shadowing violations happen while defining new
986 /// items, or if the original item wasn't defined.
987 pub fn alias(
988 &mut self,
989 module: &str,
990 name: &str,
991 as_module: &str,
992 as_name: &str,
993 ) -> Result<&mut Self> {
994 let src = self.import_key(module, Some(name));
995 let dst = self.import_key(as_module, Some(as_name));
996 match self.map.get(&src).cloned() {
997 Some(item) => self.insert(dst, item)?,
998 None => bail!("no item named `{}::{}` defined", module, name),
999 }
1000 Ok(self)
1001 }
1002
1003 /// Aliases one module's name as another.
1004 ///
1005 /// This method will alias all currently defined under `module` to also be
1006 /// defined under the name `as_module` too.
1007 ///
1008 /// # Errors
1009 ///
1010 /// Returns an error if any shadowing violations happen while defining new
1011 /// items.
1012 pub fn alias_module(&mut self, module: &str, as_module: &str) -> Result<()> {
1013 let module = self.intern_str(module);
1014 let as_module = self.intern_str(as_module);
1015 let items = self
1016 .map
1017 .iter()
1018 .filter(|(key, _def)| key.module == module)
1019 .map(|(key, def)| (key.name, def.clone()))
1020 .collect::<Vec<_>>();
1021 for (name, item) in items {
1022 self.insert(
1023 ImportKey {
1024 module: as_module,
1025 name,
1026 },
1027 item,
1028 )?;
1029 }
1030 Ok(())
1031 }
1032
1033 fn insert(&mut self, key: ImportKey, item: Definition) -> Result<()> {
1034 match self.map.entry(key) {
1035 Entry::Occupied(_) if !self.allow_shadowing => {
1036 let module = &self.strings[key.module];
1037 let desc = match self.strings.get(key.name) {
1038 Some(name) => format!("{module}::{name}"),
1039 None => module.to_string(),
1040 };
1041 bail!("import of `{}` defined twice", desc)
1042 }
1043 Entry::Occupied(mut o) => {
1044 o.insert(item);
1045 }
1046 Entry::Vacant(v) => {
1047 v.insert(item);
1048 }
1049 }
1050 Ok(())
1051 }
1052
1053 fn import_key(&mut self, module: &str, name: Option<&str>) -> ImportKey {
1054 ImportKey {
1055 module: self.intern_str(module),
1056 name: name
1057 .map(|name| self.intern_str(name))
1058 .unwrap_or(usize::max_value()),
1059 }
1060 }
1061
1062 fn intern_str(&mut self, string: &str) -> usize {
1063 if let Some(idx) = self.string2idx.get(string) {
1064 return *idx;
1065 }
1066 let string: Arc<str> = string.into();
1067 let idx = self.strings.len();
1068 self.strings.push(string.clone());
1069 self.string2idx.insert(string, idx);
1070 idx
1071 }
1072
1073 /// Attempts to instantiate the `module` provided.
1074 ///
1075 /// This method will attempt to assemble a list of imports that correspond
1076 /// to the imports required by the [`Module`] provided. This list
1077 /// of imports is then passed to [`Instance::new`] to continue the
1078 /// instantiation process.
1079 ///
1080 /// Each import of `module` will be looked up in this [`Linker`] and must
1081 /// have previously been defined. If it was previously defined with an
1082 /// incorrect signature or if it was not previously defined then an error
1083 /// will be returned because the import can not be satisfied.
1084 ///
1085 /// Per the WebAssembly spec, instantiation includes running the module's
1086 /// start function, if it has one (not to be confused with the `_start`
1087 /// function, which is not run).
1088 ///
1089 /// # Errors
1090 ///
1091 /// This method can fail because an import may not be found, or because
1092 /// instantiation itself may fail. For information on instantiation
1093 /// failures see [`Instance::new`]. If an import is not found, the error
1094 /// may be downcast to an [`UnknownImportError`].
1095 ///
1096 ///
1097 /// # Panics
1098 ///
1099 /// Panics if any item used to instantiate `module` is not owned by
1100 /// `store`. Additionally this will panic if the [`Engine`] that the `store`
1101 /// belongs to is different than this [`Linker`].
1102 ///
1103 /// # Examples
1104 ///
1105 /// ```
1106 /// # use wasmtime::*;
1107 /// # fn main() -> anyhow::Result<()> {
1108 /// # let engine = Engine::default();
1109 /// # let mut store = Store::new(&engine, ());
1110 /// let mut linker = Linker::new(&engine);
1111 /// linker.func_wrap("host", "double", |x: i32| x * 2)?;
1112 ///
1113 /// let wat = r#"
1114 /// (module
1115 /// (import "host" "double" (func (param i32) (result i32)))
1116 /// )
1117 /// "#;
1118 /// let module = Module::new(&engine, wat)?;
1119 /// linker.instantiate(&mut store, &module)?;
1120 /// # Ok(())
1121 /// # }
1122 /// ```
1123 pub fn instantiate(
1124 &self,
1125 mut store: impl AsContextMut<Data = T>,
1126 module: &Module,
1127 ) -> Result<Instance>
1128 where
1129 T: 'static,
1130 {
1131 self._instantiate_pre(module, Some(store.as_context_mut().0))?
1132 .instantiate(store)
1133 }
1134
1135 /// Attempts to instantiate the `module` provided. This is the same as
1136 /// [`Linker::instantiate`], except for async `Store`s.
1137 #[cfg(feature = "async")]
1138 pub async fn instantiate_async(
1139 &self,
1140 mut store: impl AsContextMut<Data = T>,
1141 module: &Module,
1142 ) -> Result<Instance>
1143 where
1144 T: Send + 'static,
1145 {
1146 self._instantiate_pre(module, Some(store.as_context_mut().0))?
1147 .instantiate_async(store)
1148 .await
1149 }
1150
1151 /// Performs all checks necessary for instantiating `module` with this
1152 /// linker, except that instantiation doesn't actually finish.
1153 ///
1154 /// This method is used for front-loading type-checking information as well
1155 /// as collecting the imports to use to instantiate a module with. The
1156 /// returned [`InstancePre`] represents a ready-to-be-instantiated module,
1157 /// which can also be instantiated multiple times if desired.
1158 ///
1159 /// # Errors
1160 ///
1161 /// Returns an error which may be downcast to an [`UnknownImportError`] if
1162 /// the module has any unresolvable imports.
1163 ///
1164 /// # Examples
1165 ///
1166 /// ```
1167 /// # use wasmtime::*;
1168 /// # fn main() -> anyhow::Result<()> {
1169 /// # let engine = Engine::default();
1170 /// # let mut store = Store::new(&engine, ());
1171 /// let mut linker = Linker::new(&engine);
1172 /// linker.func_wrap("host", "double", |x: i32| x * 2)?;
1173 ///
1174 /// let wat = r#"
1175 /// (module
1176 /// (import "host" "double" (func (param i32) (result i32)))
1177 /// )
1178 /// "#;
1179 /// let module = Module::new(&engine, wat)?;
1180 /// let instance_pre = linker.instantiate_pre(&module)?;
1181 ///
1182 /// // Finish instantiation after the type-checking has all completed...
1183 /// let instance = instance_pre.instantiate(&mut store)?;
1184 ///
1185 /// // ... and we can even continue to keep instantiating if desired!
1186 /// instance_pre.instantiate(&mut store)?;
1187 /// instance_pre.instantiate(&mut store)?;
1188 ///
1189 /// // Note that functions defined in a linker with `func_wrap` and similar
1190 /// // constructors are not owned by any particular `Store`, so we can also
1191 /// // instantiate our `instance_pre` in other stores because no imports
1192 /// // belong to the original store.
1193 /// let mut new_store = Store::new(&engine, ());
1194 /// instance_pre.instantiate(&mut new_store)?;
1195 /// # Ok(())
1196 /// # }
1197 /// ```
1198 pub fn instantiate_pre(&self, module: &Module) -> Result<InstancePre<T>>
1199 where
1200 T: 'static,
1201 {
1202 self._instantiate_pre(module, None)
1203 }
1204
1205 /// This is split out to optionally take a `store` so that when the
1206 /// `.instantiate` API is used we can get fresh up-to-date type information
1207 /// for memories and their current size, if necessary.
1208 ///
1209 /// Note that providing a `store` here is not required for correctness
1210 /// per-se. If one is not provided, such as the with the `instantiate_pre`
1211 /// API, then the type information used for memories and tables will reflect
1212 /// their size when inserted into the linker rather than their current size.
1213 /// This isn't expected to be much of a problem though since
1214 /// per-store-`Linker` types are likely using `.instantiate(..)` and
1215 /// per-`Engine` linkers don't have memories/tables in them.
1216 fn _instantiate_pre(
1217 &self,
1218 module: &Module,
1219 store: Option<&StoreOpaque>,
1220 ) -> Result<InstancePre<T>>
1221 where
1222 T: 'static,
1223 {
1224 let mut imports = module
1225 .imports()
1226 .map(|import| self._get_by_import(&import))
1227 .collect::<Result<Vec<_>, _>>()?;
1228 if let Some(store) = store {
1229 for import in imports.iter_mut() {
1230 import.update_size(store);
1231 }
1232 }
1233 unsafe { InstancePre::new(module, imports) }
1234 }
1235
1236 /// Returns an iterator over all items defined in this `Linker`, in
1237 /// arbitrary order.
1238 ///
1239 /// The iterator returned will yield 3-tuples where the first two elements
1240 /// are the module name and item name for the external item, and the third
1241 /// item is the item itself that is defined.
1242 ///
1243 /// Note that multiple `Extern` items may be defined for the same
1244 /// module/name pair.
1245 ///
1246 /// # Panics
1247 ///
1248 /// This function will panic if the `store` provided does not come from the
1249 /// same [`Engine`] that this linker was created with.
1250 pub fn iter<'a: 'p, 'p>(
1251 &'a self,
1252 mut store: impl AsContextMut<Data = T> + 'p,
1253 ) -> impl Iterator<Item = (&'a str, &'a str, Extern)> + 'p
1254 where
1255 T: 'static,
1256 {
1257 self.map.iter().map(move |(key, item)| {
1258 let store = store.as_context_mut();
1259 (
1260 &*self.strings[key.module],
1261 &*self.strings[key.name],
1262 // Should be safe since `T` is connecting the linker and store
1263 unsafe { item.to_extern(store.0) },
1264 )
1265 })
1266 }
1267
1268 /// Looks up a previously defined value in this [`Linker`], identified by
1269 /// the names provided.
1270 ///
1271 /// Returns `None` if this name was not previously defined in this
1272 /// [`Linker`].
1273 ///
1274 /// # Panics
1275 ///
1276 /// This function will panic if the `store` provided does not come from the
1277 /// same [`Engine`] that this linker was created with.
1278 pub fn get(
1279 &self,
1280 mut store: impl AsContextMut<Data = T>,
1281 module: &str,
1282 name: &str,
1283 ) -> Option<Extern>
1284 where
1285 T: 'static,
1286 {
1287 let store = store.as_context_mut().0;
1288 // Should be safe since `T` is connecting the linker and store
1289 Some(unsafe { self._get(module, name)?.to_extern(store) })
1290 }
1291
1292 fn _get(&self, module: &str, name: &str) -> Option<&Definition> {
1293 let key = ImportKey {
1294 module: *self.string2idx.get(module)?,
1295 name: *self.string2idx.get(name)?,
1296 };
1297 self.map.get(&key)
1298 }
1299
1300 /// Looks up a value in this `Linker` which matches the `import` type
1301 /// provided.
1302 ///
1303 /// Returns `None` if no match was found.
1304 ///
1305 /// # Panics
1306 ///
1307 /// This function will panic if the `store` provided does not come from the
1308 /// same [`Engine`] that this linker was created with.
1309 pub fn get_by_import(
1310 &self,
1311 mut store: impl AsContextMut<Data = T>,
1312 import: &ImportType,
1313 ) -> Option<Extern>
1314 where
1315 T: 'static,
1316 {
1317 let store = store.as_context_mut().0;
1318 // Should be safe since `T` is connecting the linker and store
1319 Some(unsafe { self._get_by_import(import).ok()?.to_extern(store) })
1320 }
1321
1322 fn _get_by_import(&self, import: &ImportType) -> Result<Definition, UnknownImportError> {
1323 match self._get(import.module(), import.name()) {
1324 Some(item) => Ok(item.clone()),
1325 None => Err(UnknownImportError::new(import)),
1326 }
1327 }
1328
1329 /// Returns the "default export" of a module.
1330 ///
1331 /// An export with an empty string is considered to be a "default export".
1332 /// "_start" is also recognized for compatibility.
1333 ///
1334 /// # Panics
1335 ///
1336 /// Panics if the default function found is not owned by `store`. This
1337 /// function will also panic if the `store` provided does not come from the
1338 /// same [`Engine`] that this linker was created with.
1339 pub fn get_default(&self, mut store: impl AsContextMut<Data = T>, module: &str) -> Result<Func>
1340 where
1341 T: 'static,
1342 {
1343 if let Some(external) = self.get(&mut store, module, "") {
1344 if let Extern::Func(func) = external {
1345 return Ok(func);
1346 }
1347 bail!("default export in '{}' is not a function", module);
1348 }
1349
1350 // For compatibility, also recognize "_start".
1351 if let Some(external) = self.get(&mut store, module, "_start") {
1352 if let Extern::Func(func) = external {
1353 return Ok(func);
1354 }
1355 bail!("`_start` in '{}' is not a function", module);
1356 }
1357
1358 // Otherwise return a no-op function.
1359 Ok(Func::wrap(store, || {}))
1360 }
1361}
1362
1363impl<T: 'static> Default for Linker<T> {
1364 fn default() -> Linker<T> {
1365 Linker::new(&Engine::default())
1366 }
1367}
1368
1369impl Definition {
1370 fn new(store: &StoreOpaque, item: Extern) -> Definition {
1371 let ty = DefinitionType::from(store, &item);
1372 Definition::Extern(item, ty)
1373 }
1374
1375 pub(crate) fn ty(&self) -> DefinitionType {
1376 match self {
1377 Definition::Extern(_, ty) => ty.clone(),
1378 Definition::HostFunc(func) => DefinitionType::Func(func.sig_index()),
1379 }
1380 }
1381
1382 /// Inserts this definition into the `store` provided.
1383 ///
1384 /// # Safety
1385 ///
1386 /// Note the unsafety here is due to calling `HostFunc::to_func`. The
1387 /// requirement here is that the `T` that was originally used to create the
1388 /// `HostFunc` matches the `T` on the store.
1389 pub(crate) unsafe fn to_extern(&self, store: &mut StoreOpaque) -> Extern {
1390 match self {
1391 Definition::Extern(e, _) => e.clone(),
1392 // SAFETY: the contract of this function is the same as what's
1393 // required of `to_func`, that `T` of the store matches the `T` of
1394 // this original definition.
1395 Definition::HostFunc(func) => unsafe { func.to_func(store).into() },
1396 }
1397 }
1398
1399 pub(crate) fn comes_from_same_store(&self, store: &StoreOpaque) -> bool {
1400 match self {
1401 Definition::Extern(e, _) => e.comes_from_same_store(store),
1402 Definition::HostFunc(_func) => true,
1403 }
1404 }
1405
1406 fn update_size(&mut self, store: &StoreOpaque) {
1407 match self {
1408 Definition::Extern(Extern::Memory(m), DefinitionType::Memory(_, size)) => {
1409 *size = m.internal_size(store);
1410 }
1411 Definition::Extern(Extern::SharedMemory(m), DefinitionType::Memory(_, size)) => {
1412 *size = m.size();
1413 }
1414 Definition::Extern(Extern::Table(m), DefinitionType::Table(_, size)) => {
1415 *size = m.internal_size(store);
1416 }
1417 _ => {}
1418 }
1419 }
1420}
1421
1422impl DefinitionType {
1423 pub(crate) fn from(store: &StoreOpaque, item: &Extern) -> DefinitionType {
1424 match item {
1425 Extern::Func(f) => DefinitionType::Func(f.type_index(store)),
1426 Extern::Table(t) => {
1427 DefinitionType::Table(*t.wasmtime_ty(store), t.internal_size(store))
1428 }
1429 Extern::Global(t) => DefinitionType::Global(*t.wasmtime_ty(store)),
1430 Extern::Memory(t) => {
1431 DefinitionType::Memory(*t.wasmtime_ty(store), t.internal_size(store))
1432 }
1433 Extern::SharedMemory(t) => DefinitionType::Memory(*t.ty().wasmtime_memory(), t.size()),
1434 Extern::Tag(t) => DefinitionType::Tag(*t.wasmtime_ty(store)),
1435 }
1436 }
1437
1438 pub(crate) fn desc(&self) -> &'static str {
1439 match self {
1440 DefinitionType::Func(_) => "function",
1441 DefinitionType::Table(..) => "table",
1442 DefinitionType::Memory(..) => "memory",
1443 DefinitionType::Global(_) => "global",
1444 DefinitionType::Tag(_) => "tag",
1445 }
1446 }
1447}
1448
1449/// Modules can be interpreted either as Commands or Reactors.
1450enum ModuleKind {
1451 /// The instance is a Command, meaning an instance is created for each
1452 /// exported function and lives for the duration of the function call.
1453 Command,
1454
1455 /// The instance is a Reactor, meaning one instance is created which
1456 /// may live across multiple calls.
1457 Reactor,
1458}
1459
1460impl ModuleKind {
1461 /// Determine whether the given module is a Command or a Reactor.
1462 fn categorize(module: &Module) -> Result<ModuleKind> {
1463 let command_start = module.get_export("_start");
1464 let reactor_start = module.get_export("_initialize");
1465 match (command_start, reactor_start) {
1466 (Some(command_start), None) => {
1467 if let Some(_) = command_start.func() {
1468 Ok(ModuleKind::Command)
1469 } else {
1470 bail!("`_start` must be a function")
1471 }
1472 }
1473 (None, Some(reactor_start)) => {
1474 if let Some(_) = reactor_start.func() {
1475 Ok(ModuleKind::Reactor)
1476 } else {
1477 bail!("`_initialize` must be a function")
1478 }
1479 }
1480 (None, None) => {
1481 // Module declares neither of the recognized functions, so treat
1482 // it as a reactor with no initialization function.
1483 Ok(ModuleKind::Reactor)
1484 }
1485 (Some(_), Some(_)) => {
1486 // Module declares itself to be both a Command and a Reactor.
1487 bail!("Program cannot be both a Command and a Reactor")
1488 }
1489 }
1490 }
1491}
1492
1493/// Error for an unresolvable import.
1494///
1495/// Returned - wrapped in an [`anyhow::Error`] - by [`Linker::instantiate`] and
1496/// related methods for modules with unresolvable imports.
1497#[derive(Clone, Debug)]
1498pub struct UnknownImportError {
1499 module: String,
1500 name: String,
1501 ty: ExternType,
1502}
1503
1504impl UnknownImportError {
1505 fn new(import: &ImportType) -> Self {
1506 Self {
1507 module: import.module().to_string(),
1508 name: import.name().to_string(),
1509 ty: import.ty(),
1510 }
1511 }
1512
1513 /// Returns the module name that the unknown import was expected to come from.
1514 pub fn module(&self) -> &str {
1515 &self.module
1516 }
1517
1518 /// Returns the field name of the module that the unknown import was expected to come from.
1519 pub fn name(&self) -> &str {
1520 &self.name
1521 }
1522
1523 /// Returns the type of the unknown import.
1524 pub fn ty(&self) -> ExternType {
1525 self.ty.clone()
1526 }
1527}
1528
1529impl fmt::Display for UnknownImportError {
1530 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1531 write!(
1532 f,
1533 "unknown import: `{}::{}` has not been defined",
1534 self.module, self.name,
1535 )
1536 }
1537}
1538
1539impl core::error::Error for UnknownImportError {}