Serialize and deserialize compilation artifacts. (#2020)

* Serialize and deserialize Module
* Use bincode to serialize
* Add wasm_module_serialize; docs
* Simple tests

Cargo.lock

@@ -2361,12 +2361,14 @@ version = "0.19.0"
 dependencies = [
  "anyhow",
  "backtrace",
+ "bincode",
  "cfg-if",
  "lazy_static",
  "libc",
  "log",
  "region",
  "rustc-demangle",
+ "serde",
  "smallvec",
  "target-lexicon",
  "tempfile",
@@ -2529,6 +2531,7 @@ dependencies = [
  "more-asserts",
  "object 0.20.0",
  "region",
+ "serde",
  "target-lexicon",
  "thiserror",
  "wasmparser 0.59.0",

cranelift/codegen/src/settings.rs

@@ -45,7 +45,7 @@ pub trait Configurable {
 }
 
 /// Collect settings values based on a template.
-#[derive(Clone)]
+#[derive(Clone, Hash)]
 pub struct Builder {
     template: &'static detail::Template,
     bytes: Box<[u8]>,
@@ -212,8 +212,10 @@ impl<'a> PredicateView<'a> {
 pub mod detail {
     use crate::constant_hash;
     use core::fmt;
+    use core::hash::Hash;
 
     /// An instruction group template.
+    #[derive(Hash)]
     pub struct Template {
         /// Name of the instruction group.
         pub name: &'static str,
@@ -281,6 +283,7 @@ pub mod detail {
     /// A setting descriptor holds the information needed to generically set and print a setting.
     ///
     /// Each settings group will be represented as a constant DESCRIPTORS array.
+    #[derive(Hash)]
     pub struct Descriptor {
         /// Lower snake-case name of setting as defined in meta.
         pub name: &'static str,
@@ -293,7 +296,7 @@ pub mod detail {
     }
 
     /// The different kind of settings along with descriptor bits that depend on the kind.
-    #[derive(Clone, Copy)]
+    #[derive(Clone, Copy, Hash)]
     pub enum Detail {
         /// A boolean setting only uses one bit, numbered from LSB.
         Bool {

crates/c-api/include/wasmtime.h

@@ -930,6 +930,37 @@ WASM_API_EXTERN void wasmtime_externref_new_with_finalizer(
  */
 WASM_API_EXTERN bool wasmtime_externref_data(wasm_val_t* val, void** datap);
 
+/**
+ * \brief This function serializes compiled module artifacts
+ *   as blob data.
+ *
+ * \param module the module
+ * \param ret if the conversion is successful, this byte vector is filled in with
+ *   the serialized compiled module.
+ *
+ * \return a non-null error if parsing fails, or returns `NULL`. If parsing
+ * fails then `ret` isn't touched.
+ *
+ * This function does not take ownership of `module`, and the caller is
+ * expected to deallocate the returned #wasmtime_error_t and #wasm_byte_vec_t.
+ */
+WASM_API_EXTERN own wasmtime_error_t* wasmtime_module_serialize(
+    wasm_module_t* module,
+    own wasm_byte_vec_t *ret
+);
+
+/**
+ * \brief Build a module from serialized data.
+ * *
+ * This function does not take ownership of any of its arguments, but the
+ * returned error and module are owned by the caller.
+ */
+WASM_API_EXTERN own wasmtime_error_t *wasmtime_module_deserialize(
+    wasm_engine_t *engine,
+    const wasm_byte_vec_t *serialized,
+    own wasm_module_t **ret
+);
+
 #undef own
 
 #ifdef __cplusplus

crates/c-api/src/module.rs

@@ -130,3 +130,63 @@ pub extern "C" fn wasm_module_obtain(
         exports,
     }))
 }
+
+#[no_mangle]
+pub extern "C" fn wasm_module_serialize(module: &wasm_module_t, ret: &mut wasm_byte_vec_t) {
+    drop(wasmtime_module_serialize(module, ret));
+}
+
+#[no_mangle]
+pub extern "C" fn wasm_module_deserialize(
+    store: &wasm_store_t,
+    binary: &wasm_byte_vec_t,
+) -> Option<Box<wasm_module_t>> {
+    let mut ret = ptr::null_mut();
+    let engine = wasm_engine_t {
+        engine: store.store.engine().clone(),
+    };
+    match wasmtime_module_deserialize(&engine, binary, &mut ret) {
+        Some(_err) => None,
+        None => {
+            assert!(!ret.is_null());
+            Some(unsafe { Box::from_raw(ret) })
+        }
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn wasmtime_module_serialize(
+    module: &wasm_module_t,
+    ret: &mut wasm_byte_vec_t,
+) -> Option<Box<wasmtime_error_t>> {
+    handle_result(module.module.serialize(), |buf| {
+        ret.set_buffer(buf);
+    })
+}
+
+#[no_mangle]
+pub extern "C" fn wasmtime_module_deserialize(
+    engine: &wasm_engine_t,
+    binary: &wasm_byte_vec_t,
+    ret: &mut *mut wasm_module_t,
+) -> Option<Box<wasmtime_error_t>> {
+    handle_result(
+        Module::deserialize(&engine.engine, binary.as_slice()),
+        |module| {
+            let imports = module
+                .imports()
+                .map(|i| wasm_importtype_t::new(i.module().to_owned(), i.name().to_owned(), i.ty()))
+                .collect::<Vec<_>>();
+            let exports = module
+                .exports()
+                .map(|e| wasm_exporttype_t::new(e.name().to_owned(), e.ty()))
+                .collect::<Vec<_>>();
+            let module = Box::new(wasm_module_t {
+                module: module,
+                imports,
+                exports,
+            });
+            *ret = Box::into_raw(module);
+        },
+    )
+}

crates/environ/src/module.rs

@@ -137,10 +137,10 @@ impl TablePlan {
 
 /// A translated WebAssembly module, excluding the function bodies and
 /// memory initializers.
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Module {
     /// A unique identifier (within this process) for this module.
-    #[serde(skip_serializing, default = "Module::next_id")]
+    #[serde(skip_serializing, skip_deserializing, default = "Module::next_id")]
     pub id: usize,
 
     /// The name of this wasm module, often found in the wasm file.
@@ -181,7 +181,7 @@ pub struct Module {
 /// This is stored within a `Module` and it implements `Hash`, unlike `Module`,
 /// and is used as part of the cache key when we load compiled modules from the
 /// global cache.
-#[derive(Debug, Hash, Serialize, Deserialize)]
+#[derive(Debug, Clone, Hash, Serialize, Deserialize)]
 pub struct ModuleLocal {
     /// Unprocessed signatures exactly as provided by `declare_signature()`.
     pub signatures: PrimaryMap<SignatureIndex, (WasmFuncType, ir::Signature)>,

crates/environ/src/module_environ.rs

@@ -9,6 +9,7 @@ use cranelift_wasm::{
     Memory, MemoryIndex, ModuleTranslationState, SignatureIndex, Table, TableIndex,
     TargetEnvironment, WasmError, WasmFuncType, WasmResult,
 };
+use serde::{Deserialize, Serialize};
 use std::convert::TryFrom;
 use std::sync::Arc;
 
@@ -450,7 +451,7 @@ pub fn translate_signature(mut sig: ir::Signature, pointer_type: ir::Type) -> ir
 
 /// A memory index and offset within that memory where a data initialization
 /// should is to be performed.
-#[derive(Clone)]
+#[derive(Clone, Serialize, Deserialize)]
 pub struct DataInitializerLocation {
     /// The index of the memory to initialize.
     pub memory_index: MemoryIndex,

crates/jit/Cargo.toml

@@ -32,6 +32,7 @@ cfg-if = "0.1.9"
 log = "0.4"
 gimli = { version = "0.21.0", default-features = false, features = ["write"] }
 object = { version = "0.20", default-features = false, features = ["write"] }
+serde = { version = "1.0.94", features = ["derive"] }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = { version = "0.3.8", features = ["winnt", "impl-default"] }

crates/jit/src/instantiate.rs

@@ -10,6 +10,7 @@ use crate::link::link_module;
 use crate::object::ObjectUnwindInfo;
 use crate::resolver::Resolver;
 use object::File as ObjectFile;
+use serde::{Deserialize, Serialize};
 use std::any::Any;
 use std::collections::HashMap;
 use std::sync::Arc;
@@ -51,27 +52,47 @@ pub enum SetupError {
     DebugInfo(#[from] anyhow::Error),
 }
 
-// Contains all compilation artifacts.
-struct CompilationArtifacts {
+/// Contains all compilation artifacts.
+#[derive(Serialize, Deserialize)]
+pub struct CompilationArtifacts {
+    /// Module metadata.
     module: Module,
+
+    /// ELF image with functions code.
     obj: Box<[u8]>,
+
+    /// Unwind information for function code.
     unwind_info: Box<[ObjectUnwindInfo]>,
+
+    /// Data initiailizers.
     data_initializers: Box<[OwnedDataInitializer]>,
+
+    /// Traps descriptors.
     traps: Traps,
+
+    /// Stack map descriptors.
     stack_maps: StackMaps,
+
+    /// Wasm to function code address map.
     address_transform: ModuleAddressMap,
+
+    /// Debug info presence flags.
+    debug_info: bool,
 }
 
 impl CompilationArtifacts {
-    fn new(compiler: &Compiler, data: &[u8]) -> Result<Self, SetupError> {
+    /// Builds compilation artifacts.
+    pub fn build(compiler: &Compiler, data: &[u8]) -> Result<Self, SetupError> {
         let environ = ModuleEnvironment::new(compiler.frontend_config(), compiler.tunables());
 
         let translation = environ
             .translate(data)
             .map_err(|error| SetupError::Compile(CompileError::Wasm(error)))?;
 
+        let debug_info = compiler.tunables().debug_info;
+
         let mut debug_data = None;
-        if compiler.tunables().debug_info {
+        if debug_info {
             // TODO Do we want to ignore invalid DWARF data?
             debug_data = Some(read_debuginfo(&data)?);
         }
@@ -110,6 +131,7 @@ impl CompilationArtifacts {
             traps,
             stack_maps,
             address_transform,
+            debug_info,
         })
     }
 }
@@ -136,6 +158,8 @@ pub struct CompiledModule {
     traps: Traps,
     stack_maps: StackMaps,
     address_transform: ModuleAddressMap,
+    obj: Box<[u8]>,
+    unwind_info: Box<[ObjectUnwindInfo]>,
 }
 
 impl CompiledModule {
@@ -145,8 +169,16 @@ impl CompiledModule {
         data: &'data [u8],
         profiler: &dyn ProfilingAgent,
     ) -> Result<Self, SetupError> {
-        let artifacts = CompilationArtifacts::new(compiler, data)?;
+        let artifacts = CompilationArtifacts::build(compiler, data)?;
+        Self::from_artifacts(artifacts, compiler.isa(), profiler)
+    }
 
+    /// Creates `CompiledModule` directly from `CompilationArtifacts`.
+    pub fn from_artifacts(
+        artifacts: CompilationArtifacts,
+        isa: &dyn TargetIsa,
+        profiler: &dyn ProfilingAgent,
+    ) -> Result<Self, SetupError> {
         let CompilationArtifacts {
             module,
             obj,
@@ -155,12 +187,13 @@ impl CompiledModule {
             traps,
             stack_maps,
             address_transform,
+            debug_info,
         } = artifacts;
 
         // Allocate all of the compiled functions into executable memory,
         // copying over their contents.
         let (code_memory, code_range, finished_functions, trampolines) =
-            build_code_memory(compiler.isa(), &obj, &module, unwind_info).map_err(|message| {
+            build_code_memory(isa, &obj, &module, &unwind_info).map_err(|message| {
                 SetupError::Instantiate(InstantiationError::Resource(format!(
                     "failed to build code memory for functions: {}",
                     message
@@ -168,7 +201,7 @@ impl CompiledModule {
             })?;
 
         // Register GDB JIT images; initialize profiler and load the wasm module.
-        let dbg_jit_registration = if compiler.tunables().debug_info {
+        let dbg_jit_registration = if debug_info {
             let bytes = create_dbg_image(obj.to_vec(), code_range, &module, &finished_functions)?;
 
             profiler.module_load(&module, &finished_functions, Some(&bytes));
@@ -194,9 +227,25 @@ impl CompiledModule {
             traps,
             stack_maps,
             address_transform,
+            obj,
+            unwind_info,
         })
     }
 
+    /// Extracts `CompilationArtifacts` from the compiled module.
+    pub fn to_compilation_artifacts(&self) -> CompilationArtifacts {
+        CompilationArtifacts {
+            module: (*self.module).clone(),
+            obj: self.obj.clone(),
+            unwind_info: self.unwind_info.clone(),
+            data_initializers: self.data_initializers.clone(),
+            traps: self.traps.clone(),
+            stack_maps: self.stack_maps.clone(),
+            address_transform: self.address_transform.clone(),
+            debug_info: self.code.dbg_jit_registration.is_some(),
+        }
+    }
+
     /// Crate an `Instance` from this `CompiledModule`.
     ///
     /// Note that if only one instance of this module is needed, it may be more
@@ -305,6 +354,7 @@ impl CompiledModule {
 
 /// Similar to `DataInitializer`, but owns its own copy of the data rather
 /// than holding a slice of the original module.
+#[derive(Clone, Serialize, Deserialize)]
 pub struct OwnedDataInitializer {
     /// The location where the initialization is to be performed.
     location: DataInitializerLocation,
@@ -340,7 +390,7 @@ fn build_code_memory(
     isa: &dyn TargetIsa,
     obj: &[u8],
     module: &Module,
-    unwind_info: Box<[ObjectUnwindInfo]>,
+    unwind_info: &Box<[ObjectUnwindInfo]>,
 ) -> Result<
     (
         CodeMemory,
@@ -354,7 +404,7 @@ fn build_code_memory(
 
     let mut code_memory = CodeMemory::new();
 
-    let allocation = code_memory.allocate_for_object(&obj, &unwind_info)?;
+    let allocation = code_memory.allocate_for_object(&obj, unwind_info)?;
 
     // Second, create a PrimaryMap from result vector of pointers.
     let mut finished_functions = PrimaryMap::new();

crates/jit/src/lib.rs

@@ -35,7 +35,7 @@ pub mod trampoline;
 
 pub use crate::code_memory::CodeMemory;
 pub use crate::compiler::{Compilation, CompilationStrategy, Compiler};
-pub use crate::instantiate::{CompiledModule, SetupError};
+pub use crate::instantiate::{CompilationArtifacts, CompiledModule, SetupError};
 pub use crate::link::link_module;
 pub use crate::resolver::{NullResolver, Resolver};
 

crates/jit/src/object.rs

@@ -3,6 +3,7 @@
 use super::trampoline::build_trampoline;
 use cranelift_frontend::FunctionBuilderContext;
 use object::write::Object;
+use serde::{Deserialize, Serialize};
 use wasmtime_debug::DwarfSection;
 use wasmtime_environ::entity::{EntityRef, PrimaryMap};
 use wasmtime_environ::isa::{unwind::UnwindInfo, TargetIsa};
@@ -13,7 +14,7 @@ use wasmtime_obj::{ObjectBuilder, ObjectBuilderTarget};
 pub use wasmtime_obj::utils;
 
 /// Unwind information for object files functions (including trampolines).
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub enum ObjectUnwindInfo {
     Func(FuncIndex, UnwindInfo),
     Trampoline(SignatureIndex, UnwindInfo),

crates/wasmtime/Cargo.toml

@@ -26,6 +26,8 @@ lazy_static = "1.4"
 log = "0.4.8"
 wat = { version = "1.0.18", optional = true }
 smallvec = "1.4.0"
+serde = { version = "1.0.94", features = ["derive"] }
+bincode = "1.2.1"
 
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = "0.3.7"

crates/wasmtime/src/module.rs

@@ -1,10 +1,10 @@
 use crate::frame_info::GlobalFrameInfoRegistration;
-use crate::runtime::Engine;
+use crate::runtime::{Config, Engine};
 use crate::types::{EntityType, ExportType, ExternType, ImportType};
-use anyhow::Result;
+use anyhow::{bail, Context, Result};
 use std::path::Path;
 use std::sync::{Arc, Mutex};
-use wasmtime_jit::CompiledModule;
+use wasmtime_jit::{CompilationArtifacts, CompiledModule};
 
 /// A compiled WebAssembly module, ready to be instantiated.
 ///
@@ -309,6 +309,51 @@ impl Module {
         })
     }
 
+    /// Serialize compilation artifacts to the buffer. See also `deseriaize`.
+    pub fn serialize(&self) -> Result<Vec<u8>> {
+        let artifacts = (
+            compiler_fingerprint(self.engine.config()),
+            self.compiled.to_compilation_artifacts(),
+        );
+
+        let mut buffer = Vec::new();
+        bincode::serialize_into(&mut buffer, &artifacts)?;
+
+        Ok(buffer)
+    }
+
+    /// Deserializes and creates a module from the compilatio nartifacts.
+    /// The `serialize` saves the compilation artifacts along with the host
+    /// fingerprint, which consists of target, compiler flags, and wasmtime
+    /// package version.
+    ///
+    /// The method will fail if fingerprints of current host and serialized
+    /// one are different. The method does not verify the serialized artifacts
+    /// for modifications or curruptions. All responsibily of signing and its
+    /// verification falls on the embedder.
+    pub fn deserialize(engine: &Engine, serialized: &[u8]) -> Result<Module> {
+        let expected_fingerprint = compiler_fingerprint(engine.config());
+
+        let (fingerprint, artifacts) =
+            bincode::deserialize_from::<_, (u64, CompilationArtifacts)>(serialized)
+                .context("Deserialize compilation artifacts")?;
+        if fingerprint != expected_fingerprint {
+            bail!("Incompatible compilation artifact");
+        }
+
+        let compiled = CompiledModule::from_artifacts(
+            artifacts,
+            engine.compiler().isa(),
+            &*engine.config().profiler,
+        )?;
+
+        Ok(Module {
+            engine: engine.clone(),
+            compiled: Arc::new(compiled),
+            frame_info_registration: Arc::new(Mutex::new(None)),
+        })
+    }
+
     pub(crate) fn compiled_module(&self) -> &CompiledModule {
         &self.compiled
     }
@@ -535,6 +580,13 @@ impl Module {
     }
 }
 
+fn compiler_fingerprint(config: &Config) -> u64 {
+    use std::hash::Hasher;
+    let mut hasher = std::collections::hash_map::DefaultHasher::new();
+    config.compiler_fingerprint(&mut hasher);
+    hasher.finish()
+}
+
 fn _assert_send_sync() {
     fn _assert<T: Send + Sync>() {}
     _assert::<Module>();

crates/wasmtime/src/runtime.rs

@@ -10,6 +10,7 @@ use std::hash::{Hash, Hasher};
 use std::path::Path;
 use std::rc::{Rc, Weak};
 use std::sync::Arc;
+use target_lexicon::Triple;
 use wasmparser::Validator;
 use wasmtime_environ::settings::{self, Configurable, SetError};
 use wasmtime_environ::{ir, isa, isa::TargetIsa, wasm, CacheConfig, Tunables};
@@ -634,6 +635,22 @@ impl Config {
             self.tunables.clone(),
         )
     }
+
+    /// Hashes/fingerprints compiler setting to ensure that compatible
+    /// compilation artifacts are used.
+    pub(crate) fn compiler_fingerprint<H>(&self, state: &mut H)
+    where
+        H: Hasher,
+    {
+        self.flags.hash(state);
+        self.tunables.hash(state);
+
+        let triple = Triple::host();
+        triple.hash(state);
+
+        // Catch accidental bugs of reusing across wasmtime versions.
+        env!("CARGO_PKG_VERSION").hash(state);
+    }
 }
 
 fn round_up_to_pages(val: u64) -> u64 {

examples/serialize.c

@@ -0,0 +1,169 @@
+/*
+Example of instantiating of the WebAssembly module and invoking its exported
+function.
+
+You can compile and run this example on Linux with:
+
+   cargo build --release -p wasmtime
+   cc examples/hello.c \
+       -I crates/c-api/include \
+       -I crates/c-api/wasm-c-api/include \
+       target/release/libwasmtime.a \
+       -lpthread -ldl -lm \
+       -o hello
+   ./hello
+
+Note that on Windows and macOS the command will be similar, but you'll need
+to tweak the `-lpthread` and such annotations as well as the name of the
+`libwasmtime.a` file on Windows.
+*/
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <wasm.h>
+#include <wasmtime.h>
+
+static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap);
+
+static wasm_trap_t* hello_callback(const wasm_val_t args[], wasm_val_t results[]) {
+  printf("Calling back...\n");
+  printf("> Hello World!\n");
+  return NULL;
+}
+
+int serialize(wasm_byte_vec_t* buffer) {
+  // Set up our compilation context. Note that we could also work with a
+  // `wasm_config_t` here to configure what feature are enabled and various
+  // compilation settings.
+  printf("Initializing...\n");
+  wasm_engine_t *engine = wasm_engine_new();
+  assert(engine != NULL);
+
+  // Read our input file, which in this case is a wasm text file.
+  FILE* file = fopen("examples/hello.wat", "r");
+  assert(file != NULL);
+  fseek(file, 0L, SEEK_END);
+  size_t file_size = ftell(file);
+  fseek(file, 0L, SEEK_SET);
+  wasm_byte_vec_t wat;
+  wasm_byte_vec_new_uninitialized(&wat, file_size);
+  assert(fread(wat.data, file_size, 1, file) == 1);
+  fclose(file);
+
+  // Parse the wat into the binary wasm format
+  wasm_byte_vec_t wasm;
+  wasmtime_error_t *error = wasmtime_wat2wasm(&wat, &wasm);
+  if (error != NULL)
+    exit_with_error("failed to parse wat", error, NULL);
+  wasm_byte_vec_delete(&wat);
+
+  // Now that we've got our binary webassembly we can compile our module
+  // and serialize into buffer.
+  printf("Compiling and serializing module...\n");
+  wasm_module_t *module = NULL;
+  error = wasmtime_module_new(engine, &wasm, &module);
+  wasm_byte_vec_delete(&wasm);
+  if (error != NULL)
+    exit_with_error("failed to compile module", error, NULL);
+  error = wasmtime_module_serialize(module, buffer);
+  wasm_module_delete(module);
+  if (error != NULL)
+    exit_with_error("failed to serialize module", error, NULL);
+
+  printf("Serialized.\n");
+
+  wasm_engine_delete(engine);
+  return 0;
+}
+
+int deserialize(wasm_byte_vec_t* buffer) {
+  // Set up our compilation context. Note that we could also work with a
+  // `wasm_config_t` here to configure what feature are enabled and various
+  // compilation settings.
+  printf("Initializing...\n");
+  wasm_engine_t *engine = wasm_engine_new();
+  assert(engine != NULL);
+
+  // With an engine we can create a *store* which is a long-lived group of wasm
+  // modules.
+  wasm_store_t *store = wasm_store_new(engine);
+  assert(store != NULL);
+
+  // Deserialize compiled module.
+  printf("Deserialize module...\n");
+  wasm_module_t *module = NULL;
+  wasmtime_error_t *error = wasmtime_module_deserialize(engine, buffer, &module);
+  if (error != NULL)
+    exit_with_error("failed to compile module", error, NULL);
+
+  // Next up we need to create the function that the wasm module imports. Here
+  // we'll be hooking up a thunk function to the `hello_callback` native
+  // function above.
+  printf("Creating callback...\n");
+  wasm_functype_t *hello_ty = wasm_functype_new_0_0();
+  wasm_func_t *hello = wasm_func_new(store, hello_ty, hello_callback);
+
+  // With our callback function we can now instantiate the compiled module,
+  // giving us an instance we can then execute exports from. Note that
+  // instantiation can trap due to execution of the `start` function, so we need
+  // to handle that here too.
+  printf("Instantiating module...\n");
+  wasm_trap_t *trap = NULL;
+  wasm_instance_t *instance = NULL;
+  const wasm_extern_t *imports[] = { wasm_func_as_extern(hello) };
+  error = wasmtime_instance_new(store, module, imports, 1, &instance, &trap);
+  if (instance == NULL)
+    exit_with_error("failed to instantiate", error, trap);
+
+  // Lookup our `run` export function
+  printf("Extracting export...\n");
+  wasm_extern_vec_t externs;
+  wasm_instance_exports(instance, &externs);
+  assert(externs.size == 1);
+  wasm_func_t *run = wasm_extern_as_func(externs.data[0]);
+  assert(run != NULL);
+
+  // And call it!
+  printf("Calling export...\n");
+  error = wasmtime_func_call(run, NULL, 0, NULL, 0, &trap);
+  if (error != NULL || trap != NULL)
+    exit_with_error("failed to call function", error, trap);
+
+  // Clean up after ourselves at this point
+  printf("All finished!\n");
+
+  wasm_extern_vec_delete(&externs);
+  wasm_instance_delete(instance);
+  wasm_module_delete(module);
+  wasm_store_delete(store);
+  wasm_engine_delete(engine);
+  return 0;
+}
+
+int main() {
+  wasm_byte_vec_t buffer;
+  if (serialize(&buffer)) {
+    return 1;
+  }
+  if (deserialize(&buffer)) {
+    return 1;
+  }
+  wasm_byte_vec_delete(&buffer);
+  return 0;
+}
+
+static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap) {
+  fprintf(stderr, "error: %s\n", message);
+  wasm_byte_vec_t error_message;
+  if (error != NULL) {
+    wasmtime_error_message(error, &error_message);
+    wasmtime_error_delete(error);
+  } else {
+    wasm_trap_message(trap, &error_message);
+    wasm_trap_delete(trap);
+  }
+  fprintf(stderr, "%.*s\n", (int) error_message.size, error_message.data);
+  wasm_byte_vec_delete(&error_message);
+  exit(1);
+}

examples/serialize.rs

@@ -0,0 +1,69 @@
+//! Small example of how to serialize compiled wasm module to the disk,
+//! and then instantiate it from the compilation artifacts.
+
+// You can execute this example with `cargo run --example serialize`
+
+use anyhow::Result;
+use wasmtime::*;
+
+fn serialize() -> Result<Vec<u8>> {
+    // Configure the initial compilation environment, creating the global
+    // `Store` structure. Note that you can also tweak configuration settings
+    // with a `Config` and an `Engine` if desired.
+    println!("Initializing...");
+    let engine = Engine::default();
+
+    // Compile the wasm binary into an in-memory instance of a `Module`.
+    println!("Compiling module...");
+    let module = Module::from_file(&engine, "examples/hello.wat")?;
+    let serialized = module.serialize()?;
+
+    println!("Serialized.");
+    Ok(serialized)
+}
+
+fn deserialize(buffer: &[u8]) -> Result<()> {
+    // Configure the initial compilation environment, creating the global
+    // `Store` structure. Note that you can also tweak configuration settings
+    // with a `Config` and an `Engine` if desired.
+    println!("Initializing...");
+    let store = Store::default();
+
+    // Compile the wasm binary into an in-memory instance of a `Module`.
+    println!("Deserialize module...");
+    let module = Module::deserialize(store.engine(), buffer)?;
+
+    // Here we handle the imports of the module, which in this case is our
+    // `HelloCallback` type and its associated implementation of `Callback.
+    println!("Creating callback...");
+    let hello_func = Func::wrap(&store, || {
+        println!("Calling back...");
+        println!("> Hello World!");
+    });
+
+    // Once we've got that all set up we can then move to the instantiation
+    // phase, pairing together a compiled module as well as a set of imports.
+    // Note that this is where the wasm `start` function, if any, would run.
+    println!("Instantiating module...");
+    let imports = [hello_func.into()];
+    let instance = Instance::new(&store, &module, &imports)?;
+
+    // Next we poke around a bit to extract the `run` function from the module.
+    println!("Extracting export...");
+    let run = instance
+        .get_func("run")
+        .ok_or(anyhow::format_err!("failed to find `run` function export"))?
+        .get0::<()>()?;
+
+    // And last but not least we can call it!
+    println!("Calling export...");
+    run()?;
+
+    println!("Done.");
+    Ok(())
+}
+
+fn main() -> Result<()> {
+    let file = serialize()?;
+    deserialize(&file)
+}

tests/all/main.rs

@@ -12,6 +12,7 @@ mod instance;
 mod invoke_func_via_table;
 mod linker;
 mod memory_creator;
+mod module_serialize;
 mod name;
 mod stack_overflow;
 mod table;

tests/all/module_serialize.rs

@@ -0,0 +1,48 @@
+use anyhow::{bail, Result};
+use wasmtime::*;
+
+fn serialize(engine: &Engine, wat: &'static str) -> Result<Vec<u8>> {
+    let module = Module::new(&engine, wat)?;
+    Ok(module.serialize()?)
+}
+
+fn deserialize_and_instantiate(store: &Store, buffer: &[u8]) -> Result<Instance> {
+    let module = Module::deserialize(store.engine(), buffer)?;
+    Ok(Instance::new(&store, &module, &[])?)
+}
+
+#[test]
+fn test_module_serialize_simple() -> Result<()> {
+    let buffer = serialize(
+        &Engine::default(),
+        "(module (func (export \"run\") (result i32) i32.const 42))",
+    )?;
+
+    let store = Store::default();
+    let instance = deserialize_and_instantiate(&store, &buffer)?;
+    let run = instance
+        .get_func("run")
+        .ok_or(anyhow::format_err!("failed to find `run` function export"))?
+        .get0::<i32>()?;
+    let result = run()?;
+
+    assert_eq!(42, result);
+    Ok(())
+}
+
+#[test]
+fn test_module_serialize_fail() -> Result<()> {
+    let buffer = serialize(
+        &Engine::default(),
+        "(module (func (export \"run\") (result i32) i32.const 42))",
+    )?;
+
+    let mut config = Config::new();
+    config.cranelift_opt_level(OptLevel::None);
+    let store = Store::new(&Engine::new(&config));
+    match deserialize_and_instantiate(&store, &buffer) {
+        Ok(_) => bail!("expected failure at deserialization"),
+        Err(_) => (),
+    }
+    Ok(())
+}