feat: expose building a CompiledPlugin with a fuel limit (#883)

Expose a new method `extism_compiled_plugin_new_with_fuel_limit` to
build a CompiledPlugin with a fuel limit.

Fixes #882

runtime/Cargo.toml

@@ -9,7 +9,7 @@ repository.workspace = true
 version.workspace = true
 
 [dependencies]
-wasmtime = { version = ">= 27.0.0, < 31.0.0", default-features = false, features = [
+wasmtime = { version="37", default-features = false, features = [
   'cache',
   'gc',
   'gc-drc',
@@ -20,8 +20,8 @@ wasmtime = { version = ">= 27.0.0, < 31.0.0", default-features = false, features
   'pooling-allocator',
   'demangle',
 ] }
-wasi-common = { version = ">= 27.0.0, < 31.0.0" }
-wiggle = { version = ">= 27.0.0, < 31.0.0" }
+wasi-common = "37"
+wiggle = "37"
 anyhow = "1"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
@@ -43,18 +43,20 @@ libc = "0.2"
 
 [features]
 default = ["http", "register-http", "register-filesystem", "wasmtime-default-features"]
-register-http = ["ureq"]                                   # enables wasm to be downloaded using http
-register-filesystem = []                                   # enables wasm to be loaded from disk
-http = ["ureq"]                                            # enables extism_http_request
+register-http = ["ureq"]           # enables wasm to be downloaded using http
+register-filesystem = []           # enables wasm to be loaded from disk
+http = ["ureq"]                    # enables extism_http_request
+wasmtime-exceptions = []           # enables exception-handling proposal in wasmtime (requires wasmtime gc feature)
 wasmtime-default-features = [
   'wasmtime/default',
 ]
 
+
 [build-dependencies]
 cbindgen = { version = "0.29", default-features = false }
 
 [dev-dependencies]
-criterion = "0.6.0"
+criterion = "0.7.0"
 quickcheck = "1"
 rand = "0.9.0"
 

runtime/extism.h

@@ -191,6 +191,17 @@ ExtismCompiledPlugin *extism_compiled_plugin_new(const uint8_t *wasm,
                                                  bool with_wasi,
                                                  char **errmsg);
 
+/**
+ * Pre-compile an Extism plugin and set the number of instructions a plugin is allowed to execute
+ */
+ExtismCompiledPlugin *extism_compiled_plugin_new_with_fuel_limit(const uint8_t *wasm,
+                                                                 ExtismSize wasm_size,
+                                                                 const ExtismFunction **functions,
+                                                                 ExtismSize n_functions,
+                                                                 bool with_wasi,
+                                                                 uint64_t fuel_limit,
+                                                                 char **errmsg);
+
 /**
  * Free `ExtismCompiledPlugin`
  */

runtime/src/plugin.rs

@@ -1,6 +1,7 @@
 use std::{
     any::Any,
     collections::{BTreeMap, BTreeSet},
+    path::PathBuf,
     sync::TryLockError,
 };
 
@@ -60,26 +61,16 @@ impl CompiledPlugin {
             .wasm_tail_call(true)
             .wasm_function_references(true)
             .wasm_gc(true);
+        #[cfg(feature = "wasmtime-exceptions")]
+        {
+            config.wasm_exceptions(true);
+        }
 
         if builder.options.fuel.is_some() {
             config.consume_fuel(true);
         }
 
-        match &builder.options.cache_config {
-            Some(None) => (),
-            Some(Some(path)) => {
-                config.cache_config_load(path)?;
-            }
-            None => {
-                if let Ok(env) = std::env::var("EXTISM_CACHE_CONFIG") {
-                    if !env.is_empty() {
-                        config.cache_config_load(&env)?;
-                    }
-                } else {
-                    config.cache_config_load_default()?;
-                }
-            }
-        }
+        config.cache(Self::configure_cache(&builder.options.cache_config)?);
 
         let engine = Engine::new(&config)?;
 
@@ -97,6 +88,43 @@ impl CompiledPlugin {
             engine,
         })
     }
+
+    /// Return optional cache according to builder options.
+    fn configure_cache(
+        cache_opt: &Option<Option<std::path::PathBuf>>,
+    ) -> Result<Option<wasmtime::Cache>, Error> {
+        match cache_opt {
+            // Explicitly disabled
+            Some(None) => Ok(None),
+
+            // Explicit path
+            Some(Some(p)) => {
+                let cache = wasmtime::Cache::from_file(Some(p.as_path()))?;
+                Ok(Some(cache))
+            }
+
+            // Unspecified, try environment, then system fallback
+            None => {
+                match std::env::var_os("EXTISM_CACHE_CONFIG") {
+                    Some(val) => {
+                        if val.is_empty() {
+                            // Disable cache if env var exists but is empty
+                            Ok(None)
+                        } else {
+                            let p = PathBuf::from(val);
+                            let cache = wasmtime::Cache::from_file(Some(p.as_path()))?;
+                            Ok(Some(cache))
+                        }
+                    }
+                    None => {
+                        // load cache configuration from the system default path
+                        let cache = wasmtime::Cache::from_file(None)?;
+                        Ok(Some(cache))
+                    }
+                }
+            }
+        }
+    }
 }
 
 /// Plugin contains everything needed to execute a WASM function
@@ -344,6 +372,7 @@ fn relink(
                 let (kind, ty) = match import.ty() {
                     ExternType::Func(t) => ("function", t.to_string()),
                     ExternType::Global(t) => ("global", t.content().to_string()),
+                    ExternType::Tag(t) => ("tag", t.ty().to_string()),
                     ExternType::Table(t) => ("table", t.element().to_string()),
                     ExternType::Memory(_) => ("memory", String::new()),
                 };

runtime/src/pool.rs

@@ -49,7 +49,7 @@ impl PoolPlugin {
     }
 
     /// Access the underlying plugin
-    pub fn plugin(&self) -> std::cell::RefMut<Plugin> {
+    pub fn plugin(&self) -> std::cell::RefMut<'_, Plugin> {
         self.0.borrow_mut()
     }
 

runtime/src/sdk.rs

@@ -363,6 +363,70 @@ pub unsafe extern "C" fn extism_compiled_plugin_new(
         })
 }
 
+/// Pre-compile an Extism plugin and set the number of instructions a plugin is allowed to execute
+#[no_mangle]
+pub unsafe extern "C" fn extism_compiled_plugin_new_with_fuel_limit(
+    wasm: *const u8,
+    wasm_size: Size,
+    functions: *mut *const ExtismFunction,
+    n_functions: Size,
+    with_wasi: bool,
+    fuel_limit: u64,
+    errmsg: *mut *mut std::ffi::c_char,
+) -> *mut CompiledPlugin {
+    trace!("Call to extism_plugin_new with wasm pointer {:?}", wasm);
+    let data = std::slice::from_raw_parts(wasm, wasm_size as usize);
+
+    let mut builder = PluginBuilder::new(data)
+        .with_wasi(with_wasi)
+        .with_fuel_limit(fuel_limit);
+
+    if !functions.is_null() {
+        let funcs = (0..n_functions)
+            .map(|i| unsafe { *functions.add(i as usize) })
+            .map(|ptr| {
+                if ptr.is_null() {
+                    return Err("Cannot pass null pointer");
+                }
+
+                let ExtismFunction(func) = &*ptr;
+                let Some(func) = func.take() else {
+                    return Err("Function cannot be registered with multiple different Plugins");
+                };
+
+                Ok(func)
+            })
+            .collect::<Result<Vec<_>, _>>()
+            .unwrap_or_else(|e| {
+                if !errmsg.is_null() {
+                    let e = std::ffi::CString::new(e.to_string()).unwrap();
+                    *errmsg = e.into_raw();
+                }
+                Vec::new()
+            });
+
+        if funcs.len() != n_functions as usize {
+            return std::ptr::null_mut();
+        }
+
+        builder = builder.with_functions(funcs);
+    }
+
+    CompiledPlugin::new(builder)
+        .map(|v| Box::into_raw(Box::new(v)))
+        .unwrap_or_else(|e| {
+            if !errmsg.is_null() {
+                let e = std::ffi::CString::new(format!(
+                    "Unable to compile Extism plugin: {}",
+                    e.root_cause(),
+                ))
+                .unwrap();
+                *errmsg = e.into_raw();
+            }
+            std::ptr::null_mut()
+        })
+}
+
 /// Free `ExtismCompiledPlugin`
 #[no_mangle]
 pub unsafe extern "C" fn extism_compiled_plugin_free(plugin: *mut CompiledPlugin) {