ci: re-organize release workflow

Fixes #816

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @zshipko

.github/workflows/ci.yml

@@ -1,4 +1,4 @@
-on: 
+on:
   pull_request:
     paths:
       - .github/actions/extism/**
@@ -116,4 +116,9 @@ jobs:
           path: target/**
           key: ${{ runner.os }}-target-${{ github.sha }}
       - run: cargo install cargo-criterion
-      - run: cargo criterion
+      - run:
+          cargo criterion
+      - run: |
+          git fetch
+          git checkout main
+          cargo criterion

.github/workflows/release-dotnet-native.yaml

@@ -1,4 +1,6 @@
 on:
+  release:
+    types: [published, edited]
   workflow_dispatch:
 
 name: Release .NET Native NuGet Packages
@@ -18,7 +20,7 @@ jobs:
         uses: actions/setup-dotnet@v3.0.3
         with:
            dotnet-version: 7.x
-      - uses: dawidd6/action-download-artifact@v2
+      - uses: dawidd6/action-download-artifact@v6
         with:
           workflow: release.yml
           name: release-artifacts

.github/workflows/release.yml

@@ -38,6 +38,20 @@ jobs:
             static-dll-artifact: ''
             pc-in: 'extism.pc.in'
             static-pc-in: 'extism-static.pc.in'
+          - os: 'ubuntu'
+            target: 'aarch64-linux-android'
+            artifact: 'libextism.so'
+            static-artifact: 'libextism.a'
+            static-dll-artifact: ''
+            pc-in: 'extism.pc.in'
+            static-pc-in: 'extism-static.pc.in'
+          - os: 'ubuntu'
+            target: 'x86_64-linux-android'
+            artifact: 'libextism.so'
+            static-artifact: 'libextism.a'
+            static-dll-artifact: ''
+            pc-in: 'extism.pc.in'
+            static-pc-in: 'extism-static.pc.in'
           - os: 'ubuntu'
             target: 'aarch64-unknown-linux-gnu'
             artifact: 'libextism.so'
@@ -61,10 +75,10 @@ jobs:
             static-pc-in: 'extism-static.pc.in'
           - os: 'ubuntu'
             target: 'x86_64-unknown-linux-musl'
-            artifact: ''
+            artifact: 'libextism.so'
             static-artifact: 'libextism.a'
             static-dll-artifact: ''
-            pc-in: ''
+            pc-in: 'extism.pc.in'
             static-pc-in: 'extism-static.pc.in'
           - os: 'windows'
             target: 'x86_64-pc-windows-gnu'
@@ -98,13 +112,11 @@ jobs:
           pyproject="$(cat extism-maturin/pyproject.toml)"
           <<<"$pyproject" >extism-maturin/pyproject.toml sed -e 's/^version = "0.0.0.replaced-by-ci"/version = "'"$version"'"/g'
 
-      - name: Install Rust
-        uses: actions-rs/toolchain@v1
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: stable
-          profile: minimal
-          override: true
           target: ${{ matrix.target }}
+          override: true
+          toolchain: stable
 
       - uses: Swatinem/rust-cache@v2
         with:
@@ -113,11 +125,15 @@ jobs:
           cache-on-failure: "true"
 
       - name: Build Target (${{ matrix.os }} ${{ matrix.target }})
-        uses: actions-rs/cargo@v1
-        with:
-          use-cross: ${{ matrix.os != 'windows' }}
-          command: build
-          args: --release --target ${{ matrix.target }} -p ${{ env.RUNTIME_CRATE }}
+        if: ${{ matrix.os != 'windows' }}
+        run: |
+          cargo install cross
+          cross build --release --target ${{ matrix.target }} -p ${{ env.RUNTIME_CRATE }}
+
+      - name: Build Target (${{ matrix.os }} ${{ matrix.target }})
+        if: ${{ matrix.os == 'windows' }}
+        run: |
+          cargo build --release --target ${{ matrix.target }} -p ${{ env.RUNTIME_CRATE }}
 
       - uses: actions/setup-python@v4
         with:

README.md

@@ -8,7 +8,7 @@
 
 [![Discord](https://img.shields.io/discord/1011124058408112148?color=%23404eed&label=Community%20Chat&logo=Discord&logoColor=%23404eed)](https://extism.org/discord)
 ![GitHub Org's stars](https://img.shields.io/github/stars/extism)
-![Downloads](https://img.shields.io/crates/d/extism)
+![Downloads](https://img.shields.io/crates/d/extism-manifest)
 ![GitHub License](https://img.shields.io/github/license/extism/extism)
 ![GitHub release (with filter)](https://img.shields.io/github/v/release/extism/extism)
 
@@ -61,11 +61,11 @@ started:
 
 # Compile WebAssembly to run in Extism Hosts
 
-Extism Hosts (running the SDK) must execute WebAssembly code that has a PDK
-library compiled in to the `.wasm` binary. PDKs make it easy for plug-in /
-extension code authors to read input from the host and return data back, read
-provided configuration, set/get variables, make outbound HTTP calls if allowed,
-and more.
+Extism Hosts (running the SDK) must execute WebAssembly code that has a
+[PDK, or Plug-in Development Kit](https://extism.org/docs/concepts/pdk), library
+compiled in to the `.wasm` binary. PDKs make it easy for plug-in / extension
+code authors to read input from the host and return data back, read provided
+configuration, set/get variables, make outbound HTTP calls if allowed, and more.
 
 Pick a PDK to import into your Wasm program, and refer to the documentation to
 get started:
@@ -74,13 +74,73 @@ get started:
 | ------------------ | ---------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------- | --------------------------------------------------------- |
 | Rust PDK           | <img alt="Rust PDK" src="https://extism.org/img/sdk-languages/rust.svg" width="50px"/>                     | https://github.com/extism/rust-pdk                            | [Crates.io](https://crates.io/crates/extism-pdk)          |
 | JS PDK             | <img alt="JS PDK" src="https://extism.org/img/sdk-languages/js.svg" width="50px"/>                         | https://github.com/extism/js-pdk                              | N/A                                                       |
+| Python PDK         | <img alt="Python PDK" src="https://extism.org/img/sdk-languages/python.svg" width="50px"/>                 | https://github.com/extism/python-pdk                          | N/A                                                       |
 | Go PDK             | <img alt="Go PDK" src="https://extism.org/img/sdk-languages/go.svg" width="50px"/>                         | https://github.com/extism/go-pdk                              | [Go mod](https://pkg.go.dev/github.com/extism/go-pdk)     |
 | Haskell PDK        | <img alt="Haskell PDK" src="https://extism.org/img/sdk-languages/haskell.svg" width="50px"/>               | https://github.com/extism/haskell-pdk                         | [Hackage](https://hackage.haskell.org/package/extism-pdk) |
 | AssemblyScript PDK | <img alt="AssemblyScript PDK" src="https://extism.org/img/sdk-languages/assemblyscript.svg" width="50px"/> | https://github.com/extism/assemblyscript-pdk                  | [NPM](https://www.npmjs.com/package/@extism/as-pdk)       |
-| .NET PDK           | <img alt=".NET PDK" src="https://extism.org/img/sdk-languages/dotnet.svg" width="50px"/>                   | https://github.com/extism/dotnet-pdk <br/>(supports C# & F#!) | https://www.nuget.org/packages/Extism.Pdk                 |
+| .NET PDK           | <img alt=".NET PDK" src="https://extism.org/img/sdk-languages/dotnet.svg" width="50px"/>                   | https://github.com/extism/dotnet-pdk <br/>(supports C# & F#!) | [Nuget](https://www.nuget.org/packages/Extism.Pdk)        |
 | C PDK              | <img alt="C PDK" src="https://extism.org/img/sdk-languages/c.svg" width="50px"/>                           | https://github.com/extism/c-pdk                               | N/A                                                       |
+| C++ PDK            | <img alt="C++ PDK" src="https://extism.org/img/sdk-languages/cpp.svg" width="50px"/>                       | https://github.com/extism/cpp-pdk                             | N/A                                                       |
 | Zig PDK            | <img alt="Zig PDK" src="https://extism.org/img/sdk-languages/zig.svg" width="50px"/>                       | https://github.com/extism/zig-pdk                             | N/A                                                       |
 
+# Generating Bindings
+
+It's often very useful to define a schema to describe the function signatures
+and types you want to use between Extism SDK and PDK languages.
+
+[XTP Bindgen](https://github.com/dylibso/xtp-bindgen) is an open source
+framework to generate PDK bindings for Extism plug-ins. It's used by the
+[XTP Platform](https://www.getxtp.com/), but can be used outside of the platform
+to define any Extism compatible plug-in system.
+
+## 1. Install the `xtp` CLI.
+
+See installation instructions
+[here](https://docs.xtp.dylibso.com/docs/cli#installation).
+
+## 2. Create a schema using our OpenAPI-inspired IDL:
+
+```yaml
+version: v1-draft
+exports: 
+  CountVowels:
+      input: 
+          type: string
+          contentType: text/plain; charset=utf-8
+      output:
+          $ref: "#/components/schemas/VowelReport"
+          contentType: application/json
+# components.schemas defined in example-schema.yaml...
+```
+
+> See an example in [example-schema.yaml](./example-schema.yaml), or a full
+> "kitchen sink" example on
+> [the docs page](https://docs.xtp.dylibso.com/docs/concepts/xtp-schema/).
+
+## 3. Generate bindings to use from your plugins:
+
+```
+xtp plugin init --schema-file ./example-schema.yaml
+  > 1. TypeScript                      
+    2. Go                              
+    3. Rust                            
+    4. Python                          
+    5. C#                              
+    6. Zig                             
+    7. C++                             
+    8. GitHub Template                 
+    9. Local Template
+```
+
+This will create an entire boilerplate plugin project for you to get started
+with. Implement the empty function(s), and run `xtp plugin build` to compile
+your plugin.
+
+> For more information about XTP Bindgen, see the
+> [dylibso/xtp-bindgen](https://github.com/dylibso/xtp-bindgen) repository and
+> the official
+> [XTP Schema documentation](https://docs.xtp.dylibso.com/docs/concepts/xtp-schema).
+
 # Support
 
 ## Discord

convert/Cargo.toml

@@ -13,7 +13,7 @@ description = "Traits to make Rust types usable with Extism"
 anyhow = "1.0.75"
 base64 = "~0.22"
 bytemuck = {version = "1.14.0", optional = true }
-prost = { version = "0.12.0", optional = true }
+prost = { version = "0.13.1", optional = true }
 protobuf = { version = "3.2.0", optional = true }
 rmp-serde = { version = "1.1.2", optional = true }
 serde = "1.0.186"

convert/src/encoding.rs

@@ -55,7 +55,7 @@ encoding!(pub Json, serde_json::to_vec, serde_json::from_slice);
 #[cfg(feature = "msgpack")]
 encoding!(pub Msgpack, rmp_serde::to_vec, rmp_serde::from_slice);
 
-impl<'a> ToBytes<'a> for serde_json::Value {
+impl ToBytes<'_> for serde_json::Value {
     type Bytes = Vec<u8>;
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -85,7 +85,7 @@ impl<T: AsRef<[u8]>> From<T> for Base64<T> {
     }
 }
 
-impl<'a, T: AsRef<[u8]>> ToBytes<'a> for Base64<T> {
+impl<T: AsRef<[u8]>> ToBytes<'_> for Base64<T> {
     type Bytes = String;
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -124,7 +124,7 @@ impl<T: prost::Message> From<T> for Prost<T> {
 }
 
 #[cfg(feature = "prost")]
-impl<'a, T: prost::Message> ToBytes<'a> for Prost<T> {
+impl<T: prost::Message> ToBytes<'_> for Prost<T> {
     type Bytes = Vec<u8>;
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -146,7 +146,7 @@ impl<T: Default + prost::Message> FromBytesOwned for Prost<T> {
 pub struct Protobuf<T: protobuf::Message>(pub T);
 
 #[cfg(feature = "protobuf")]
-impl<'a, T: protobuf::Message> ToBytes<'a> for Protobuf<T> {
+impl<T: protobuf::Message> ToBytes<'_> for Protobuf<T> {
     type Bytes = Vec<u8>;
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {

convert/src/tests.rs

@@ -62,7 +62,7 @@ fn rountrip_option() {
 }
 
 #[cfg(all(feature = "raw", target_endian = "little"))]
-mod tests {
+mod raw_tests {
     use crate::*;
 
     #[test]
@@ -81,10 +81,10 @@ mod tests {
             c: true,
         };
         let raw = Raw(&x).to_bytes().unwrap();
-        let y = Raw::from_bytes(&raw).unwrap();
+        let y = Raw::from_bytes(raw).unwrap();
         assert_eq!(&x, y.0);
 
-        let y: Result<Raw<[u8; std::mem::size_of::<TestRaw>()]>, Error> = Raw::from_bytes(&raw);
+        let y: Result<Raw<[u8; std::mem::size_of::<TestRaw>()]>, Error> = Raw::from_bytes(raw);
         assert!(y.is_ok());
     }
 }

convert/src/to_bytes.rs

@@ -61,21 +61,21 @@ pub trait ToBytes<'a> {
     fn to_bytes(&self) -> Result<Self::Bytes, Error>;
 }
 
-impl<'a> ToBytes<'a> for () {
+impl ToBytes<'_> for () {
     type Bytes = [u8; 0];
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
         Ok([])
     }
 }
 
-impl<'a> ToBytes<'a> for Vec<u8> {
+impl ToBytes<'_> for Vec<u8> {
     type Bytes = Vec<u8>;
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
         Ok(self.clone())
     }
 }
 
-impl<'a> ToBytes<'a> for String {
+impl ToBytes<'_> for String {
     type Bytes = String;
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
         Ok(self.clone())
@@ -96,7 +96,7 @@ impl<'a> ToBytes<'a> for &'a str {
     }
 }
 
-impl<'a> ToBytes<'a> for f64 {
+impl ToBytes<'_> for f64 {
     type Bytes = [u8; 8];
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -104,7 +104,7 @@ impl<'a> ToBytes<'a> for f64 {
     }
 }
 
-impl<'a> ToBytes<'a> for f32 {
+impl ToBytes<'_> for f32 {
     type Bytes = [u8; 4];
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -112,7 +112,7 @@ impl<'a> ToBytes<'a> for f32 {
     }
 }
 
-impl<'a> ToBytes<'a> for i64 {
+impl ToBytes<'_> for i64 {
     type Bytes = [u8; 8];
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -120,7 +120,7 @@ impl<'a> ToBytes<'a> for i64 {
     }
 }
 
-impl<'a> ToBytes<'a> for i32 {
+impl ToBytes<'_> for i32 {
     type Bytes = [u8; 4];
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -128,7 +128,7 @@ impl<'a> ToBytes<'a> for i32 {
     }
 }
 
-impl<'a> ToBytes<'a> for u64 {
+impl ToBytes<'_> for u64 {
     type Bytes = [u8; 8];
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {
@@ -136,7 +136,7 @@ impl<'a> ToBytes<'a> for u64 {
     }
 }
 
-impl<'a> ToBytes<'a> for u32 {
+impl ToBytes<'_> for u32 {
     type Bytes = [u8; 4];
 
     fn to_bytes(&self) -> Result<Self::Bytes, Error> {

example-schema.yaml

@@ -0,0 +1,28 @@
+# yaml-language-server: $schema=https://xtp.dylibso.com/assets/wasm/schema.json
+# Learn more at https://docs.xtp.dylibso.com/docs/concepts/xtp-schema
+version: v1-draft
+exports: 
+  CountVowels:
+      input: 
+          type: string
+          contentType: text/plain; charset=utf-8
+      output:
+          $ref: "#/components/schemas/VowelReport"
+          contentType: application/json
+components:
+  schemas:
+    VowelReport:
+      description: The result of counting vowels on the Vowels input.
+      properties:
+        count:
+          type: integer
+          format: int32
+          description: The count of vowels for input string.
+        total:
+          type: integer
+          format: int32
+          description: The cumulative amount of vowels counted, if this keeps state across multiple function calls.
+          nullable: true
+        vowels:
+          type: string
+          description: The set of vowels used to get the count, e.g. "aAeEiIoOuU"

kernel/src/lib.rs

@@ -255,15 +255,6 @@ impl MemoryRoot {
     pub unsafe fn alloc(&mut self, length: u64) -> Option<&'static mut MemoryBlock> {
         let self_position = self.position.load(Ordering::Acquire);
         let self_length = self.length.load(Ordering::Acquire);
-        let b = self.find_free_block(length, self_position);
-
-        // If there's a free block then re-use it
-        if let Some(b) = b {
-            b.used = length as usize;
-            b.status
-                .store(MemoryStatus::Active as u8, Ordering::Release);
-            return Some(b);
-        }
 
         // Get the current index for a new block
         let curr = self.blocks.as_ptr() as u64 + self_position;
@@ -275,6 +266,21 @@ impl MemoryRoot {
         // When the allocation is larger than the number of bytes available
         // we will need to try to grow the memory
         if length_with_block >= mem_left {
+            // If the current position is large enough to hold the length of the block being
+            // allocated then check for existing free blocks that can be re-used before
+            // growing memory
+            if length_with_block <= self_position {
+                let b = self.find_free_block(length, self_position);
+
+                // If there's a free block then re-use it
+                if let Some(b) = b {
+                    b.used = length as usize;
+                    b.status
+                        .store(MemoryStatus::Active as u8, Ordering::Release);
+                    return Some(b);
+                }
+            }
+
             // Calculate the number of pages needed to cover the remaining bytes
             let npages = num_pages(length_with_block - mem_left);
             let x = core::arch::wasm32::memory_grow(0, npages);
@@ -489,6 +495,8 @@ pub unsafe fn store_u64(p: Pointer, x: u64) {
 /// Set the range of the input data in memory
 /// h must always be a handle so that length works on it
 /// len must match length(handle)
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 #[no_mangle]
 pub unsafe fn input_set(h: Handle, len: u64) {
     let root = MemoryRoot::new();
@@ -503,6 +511,8 @@ pub unsafe fn input_set(h: Handle, len: u64) {
 }
 
 /// Set the range of the output data in memory
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 #[no_mangle]
 pub unsafe fn output_set(p: Pointer, len: u64) {
     let root = MemoryRoot::new();
@@ -548,6 +558,8 @@ pub unsafe fn reset() {
 
 /// Set the error message offset, the handle passed to this
 /// function should not be freed after this call
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 #[no_mangle]
 pub unsafe fn error_set(h: Handle) {
     let root = MemoryRoot::new();
@@ -582,45 +594,6 @@ mod test {
     use crate::*;
     use wasm_bindgen_test::*;
 
-    // See https://github.com/extism/extism/pull/659
-    #[wasm_bindgen_test]
-    fn test_659() {
-        unsafe {
-            // Warning: These offsets will need to change if we adjust the kernel memory layout at all
-            reset();
-            assert_eq!(alloc(1065), 77);
-            assert_eq!(alloc(288), 1154);
-            assert_eq!(alloc(128), 1454);
-            assert_eq!(length(1154), 288);
-            assert_eq!(length(1454), 128);
-            free(1454);
-            assert_eq!(alloc(213), 1594);
-            length_unsafe(1594);
-            assert_eq!(alloc(511), 1819);
-            assert_eq!(alloc(4), 1454);
-            assert_eq!(length(1454), 4);
-            assert_eq!(length(1819), 511);
-            assert_eq!(alloc(13), 2342);
-            assert_eq!(length(2342), 13);
-            assert_eq!(alloc(336), 2367);
-            assert_eq!(alloc(1077), 2715);
-            assert_eq!(length(2367), 336);
-            assert_eq!(length(2715), 1077);
-            free(2715);
-            assert_eq!(alloc(1094), 3804);
-            length_unsafe(3804);
-
-            // Allocate 4 bytes, expect to receive address 3788
-            assert_eq!(alloc(4), 3788);
-
-            assert_eq!(alloc(4), 3772);
-            assert_eq!(length(3772), 4);
-
-            // Address 3788 has not been freed yet, so expect it to have 4 bytes allocated
-            assert_eq!(length(3788), 4);
-        }
-    }
-
     #[wasm_bindgen_test]
     fn test_oom() {
         let size = 1024 * 1024 * 5;

manifest/src/lib.rs

@@ -269,8 +269,8 @@ pub struct Manifest {
     /// Config values are made accessible using the PDK `extism_config_get` function
     #[serde(default)]
     pub config: BTreeMap<String, String>,
-    #[serde(default)]
 
+    #[serde(default)]
     /// Specifies which hosts may be accessed via HTTP, if this is empty then
     /// no hosts may be accessed. Wildcards may be used.
     pub allowed_hosts: Option<Vec<String>>,
@@ -417,14 +417,14 @@ mod wasmdata {
     }
 }
 
-impl<'a> From<Manifest> for std::borrow::Cow<'a, [u8]> {
+impl From<Manifest> for std::borrow::Cow<'_, [u8]> {
     fn from(m: Manifest) -> Self {
         let s = serde_json::to_vec(&m).unwrap();
         std::borrow::Cow::Owned(s)
     }
 }
 
-impl<'a> From<&Manifest> for std::borrow::Cow<'a, [u8]> {
+impl From<&Manifest> for std::borrow::Cow<'_, [u8]> {
     fn from(m: &Manifest) -> Self {
         let s = serde_json::to_vec(&m).unwrap();
         std::borrow::Cow::Owned(s)

runtime/Cargo.toml

@@ -9,9 +9,9 @@ repository.workspace = true
 version.workspace = true
 
 [dependencies]
-wasmtime = ">= 20.0.0, < 23.0.0"
-wasi-common = ">= 20.0.0, < 23.0.0"
-wiggle = ">= 20.0.0, < 23.0.0"
+wasmtime = {version = ">= 26.0.0, < 27.0.0"}
+wasi-common = {version = ">= 26.0.0, < 27.0.0"}
+wiggle = {version = ">= 26.0.0, < 27.0.0"}
 anyhow = "1"
 serde = {version = "1", features = ["derive"]}
 serde_json = "1"
@@ -34,7 +34,7 @@ register-filesystem = [] # enables wasm to be loaded from disk
 http = ["ureq"]          # enables extism_http_request
 
 [build-dependencies]
-cbindgen = { version = "0.26", default-features = false }
+cbindgen = { version = "0.28", default-features = false }
 
 [dev-dependencies]
 criterion = "0.5.1"

runtime/benches/bench.rs

@@ -6,6 +6,7 @@ const COUNT_VOWELS: &[u8] = include_bytes!("../../wasm/code.wasm");
 const REFLECT: &[u8] = include_bytes!("../../wasm/reflect.wasm");
 const ECHO: &[u8] = include_bytes!("../../wasm/echo.wasm");
 const CONSUME: &[u8] = include_bytes!("../../wasm/consume.wasm");
+const ALLOCATIONS: &[u8] = include_bytes!("../../wasm/allocations.wasm");
 
 host_fn!(hello_world (a: String) -> String { Ok(a) });
 
@@ -35,6 +36,31 @@ pub fn create_plugin(c: &mut Criterion) {
     });
 }
 
+pub fn create_compiled(c: &mut Criterion) {
+    let mut g = c.benchmark_group("create");
+    g.noise_threshold(1.0);
+    g.significance_level(0.2);
+    g.bench_function("create_compiled", |b| {
+        b.iter(|| {
+            let plugin = PluginBuilder::new(COUNT_VOWELS).with_wasi(true);
+            let _compiled = CompiledPlugin::new(plugin).unwrap();
+        })
+    });
+}
+
+pub fn create_plugin_compiled(c: &mut Criterion) {
+    let mut g = c.benchmark_group("create");
+    g.noise_threshold(1.0);
+    g.significance_level(0.2);
+    let plugin = PluginBuilder::new(COUNT_VOWELS).with_wasi(true);
+    let compiled = CompiledPlugin::new(plugin).unwrap();
+    g.bench_function("create_plugin_compiled", |b| {
+        b.iter(|| {
+            let _plugin = Plugin::new_from_compiled(&compiled).unwrap();
+        })
+    });
+}
+
 pub fn create_plugin_no_cache(c: &mut Criterion) {
     let mut g = c.benchmark_group("create");
     g.noise_threshold(1.0);
@@ -168,6 +194,17 @@ pub fn reflect(c: &mut Criterion) {
     }
 }
 
+pub fn allocations(c: &mut Criterion) {
+    let mut g = c.benchmark_group("allocations");
+
+    let mut plugin = PluginBuilder::new(ALLOCATIONS).build().unwrap();
+    g.bench_function("allocations", |b| {
+        b.iter(|| {
+            plugin.call::<_, ()>("allocations", "").unwrap();
+        })
+    });
+}
+
 // This is an apples-to-apples comparison of a linked wasm "reflect" function to our host "reflect"
 // function.
 pub fn reflect_linked(c: &mut Criterion) {
@@ -260,13 +297,16 @@ pub fn reflect_linked(c: &mut Criterion) {
 
 criterion_group!(
     benches,
+    allocations,
     consume,
     echo,
     reflect,
     reflect_linked,
     basic,
     create_plugin,
+    create_plugin_compiled,
     create_plugin_no_cache,
+    create_compiled,
     count_vowels
 );
 criterion_main!(benches);

runtime/build.rs

@@ -24,6 +24,7 @@ fn main() {
         .rename_item("CurrentPlugin", "ExtismCurrentPlugin")
         .rename_item("CancelHandle", "ExtismCancelHandle")
         .rename_item("Plugin", "ExtismPlugin")
+        .rename_item("CompiledPlugin", "ExtismCompiledPlugin")
         .rename_item("Function", "ExtismFunction")
         .with_style(cbindgen::Style::Type)
         .generate()

runtime/examples/fs.rs

@@ -2,6 +2,8 @@ use extism::*;
 fn main() {
     let url = Wasm::file("../wasm/read_write.wasm");
     let manifest = Manifest::new([url])
+        // This will fail because we're using a readonly path (specified with the `ro:` prefix)
+        // to overwrite the data file, remove `ro:` from the path on the following line
         .with_allowed_path("ro:src/tests/data".to_string(), "/data")
         .with_config_key("path", "/data/data.txt");
 
@@ -18,6 +20,7 @@ fn main() {
 
     println!("-----------------------------------------------------");
 
+    // If the allowed path is readonly then writing back to the file should fail
     println!("trying to write file: ");
     let line = format!(
         "Hello World at {:?}\n",

runtime/extism.h

@@ -52,6 +52,8 @@ typedef enum {
  */
 typedef struct ExtismCancelHandle ExtismCancelHandle;
 
+typedef struct ExtismCompiledPlugin ExtismCompiledPlugin;
+
 /**
  * CurrentPlugin stores data that is available to the caller in PDK functions, this should
  * only be accessed from inside a host function
@@ -179,6 +181,21 @@ void extism_function_free(ExtismFunction *f);
  */
 void extism_function_set_namespace(ExtismFunction *ptr, const char *namespace_);
 
+/**
+ * Pre-compile an Extism plugin
+ */
+ExtismCompiledPlugin *extism_compiled_plugin_new(const uint8_t *wasm,
+                                                 ExtismSize wasm_size,
+                                                 const ExtismFunction **functions,
+                                                 ExtismSize n_functions,
+                                                 bool with_wasi,
+                                                 char **errmsg);
+
+/**
+ * Free `ExtismCompiledPlugin`
+ */
+void extism_compiled_plugin_free(ExtismCompiledPlugin *plugin);
+
 /**
  * Create a new plugin with host functions, the functions passed to this function no longer need to be manually freed using
  *
@@ -195,13 +212,34 @@ ExtismPlugin *extism_plugin_new(const uint8_t *wasm,
                                 bool with_wasi,
                                 char **errmsg);
 
+/**
+ * Create a new plugin from an `ExtismCompiledPlugin`
+ */
+ExtismPlugin *extism_plugin_new_from_compiled(const ExtismCompiledPlugin *compiled, char **errmsg);
+
+/**
+ * Create a new plugin and set the number of instructions a plugin is allowed to execute
+ */
+ExtismPlugin *extism_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);
+
+/**
+ * Enable HTTP response headers in plugins using `extism:host/env::http_request`
+ */
+void extism_plugin_allow_http_response_headers(ExtismPlugin *plugin);
+
 /**
  * Free the error returned by `extism_plugin_new`, errors returned from `extism_plugin_error` don't need to be freed
  */
 void extism_plugin_new_error_free(char *err);
 
 /**
- * Remove a plugin from the registry and free associated memory
+ * Free `ExtismPlugin`
  */
 void extism_plugin_free(ExtismPlugin *plugin);
 
@@ -302,5 +340,5 @@ bool extism_plugin_reset(ExtismPlugin *plugin);
 const char *extism_version(void);
 
 #ifdef __cplusplus
-} // extern "C"
-#endif // __cplusplus
+}  // extern "C"
+#endif  // __cplusplus

runtime/src/current_plugin.rs

@@ -1,3 +1,5 @@
+use anyhow::Context;
+
 use crate::*;
 
 /// CurrentPlugin stores data that is available to the caller in PDK functions, this should
@@ -12,6 +14,7 @@ pub struct CurrentPlugin {
     pub(crate) linker: *mut wasmtime::Linker<CurrentPlugin>,
     pub(crate) wasi: Option<Wasi>,
     pub(crate) http_status: u16,
+    pub(crate) http_headers: Option<std::collections::BTreeMap<String, String>>,
     pub(crate) available_pages: Option<u32>,
     pub(crate) memory_limiter: Option<MemoryLimiter>,
     pub(crate) id: uuid::Uuid,
@@ -53,7 +56,12 @@ impl wasmtime::ResourceLimiter for MemoryLimiter {
         Ok(true)
     }
 
-    fn table_growing(&mut self, _current: u32, desired: u32, maximum: Option<u32>) -> Result<bool> {
+    fn table_growing(
+        &mut self,
+        _current: usize,
+        desired: usize,
+        maximum: Option<usize>,
+    ) -> Result<bool> {
         if let Some(max) = maximum {
             return Ok(desired <= max);
         }
@@ -160,10 +168,10 @@ impl CurrentPlugin {
     }
 
     pub fn memory_bytes_mut(&mut self, handle: MemoryHandle) -> Result<&mut [u8], Error> {
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(mem) = linker.get(&mut store, EXTISM_ENV_MODULE, "memory") {
+        let (linker, store) = self.linker_and_store();
+        if let Some(mem) = linker.get(&mut *store, EXTISM_ENV_MODULE, "memory") {
             let mem = mem.into_memory().unwrap();
-            let ptr = unsafe { mem.data_ptr(&store).add(handle.offset() as usize) };
+            let ptr = unsafe { mem.data_ptr(&*store).add(handle.offset() as usize) };
             if ptr.is_null() {
                 return Ok(&mut []);
             }
@@ -174,10 +182,10 @@ impl CurrentPlugin {
     }
 
     pub fn memory_bytes(&mut self, handle: MemoryHandle) -> Result<&[u8], Error> {
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(mem) = linker.get(&mut store, EXTISM_ENV_MODULE, "memory") {
+        let (linker, store) = self.linker_and_store();
+        if let Some(mem) = linker.get(&mut *store, EXTISM_ENV_MODULE, "memory") {
             let mem = mem.into_memory().unwrap();
-            let ptr = unsafe { mem.data_ptr(&store).add(handle.offset() as usize) };
+            let ptr = unsafe { mem.data_ptr(&*store).add(handle.offset() as usize) };
             if ptr.is_null() {
                 return Ok(&[]);
             }
@@ -187,20 +195,26 @@ impl CurrentPlugin {
         anyhow::bail!("{} unable to locate extism memory", self.id)
     }
 
-    pub fn host_context<T: Clone + 'static>(&mut self) -> Result<T, Error> {
-        let (linker, mut store) = self.linker_and_store();
-        let Some(Extern::Global(xs)) = linker.get(&mut store, EXTISM_ENV_MODULE, "extism_context")
+    pub fn host_context<T: 'static>(&mut self) -> Result<&mut T, Error> {
+        let (linker, store) = self.linker_and_store();
+        let Some(Extern::Global(xs)) = linker.get(&mut *store, EXTISM_ENV_MODULE, "extism_context")
         else {
             anyhow::bail!("unable to locate an extism kernel global: extism_context",)
         };
 
-        let Val::ExternRef(Some(xs)) = xs.get(&mut store) else {
+        let Val::ExternRef(Some(xs)) = xs.get(&mut *store) else {
             anyhow::bail!("expected extism_context to be an externref value",)
         };
 
-        match xs.data(&mut store)?.downcast_ref::<T>().cloned() {
-            Some(xs) => Ok(xs.clone()),
-            None => anyhow::bail!("could not downcast extism_context",),
+        match xs
+            .data_mut(&mut *store)?
+            .downcast_mut::<Box<dyn std::any::Any + Send + Sync>>()
+        {
+            Some(xs) => match xs.downcast_mut::<T>() {
+                Some(xs) => Ok(xs),
+                None => anyhow::bail!("could not downcast extism_context inner value"),
+            },
+            None => anyhow::bail!("could not downcast extism_context"),
         }
     }
 
@@ -214,9 +228,13 @@ impl CurrentPlugin {
         let (linker, mut store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
         if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "alloc") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(n as i64)], output)?;
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(n as i64)], output)
+                    .context("failed to allocate extism memory")
+            )?;
         } else {
             anyhow::bail!("{} unable to allocate memory", self.id);
         }
@@ -238,11 +256,15 @@ impl CurrentPlugin {
 
     /// Free a block of Extism plugin memory
     pub fn memory_free(&mut self, handle: MemoryHandle) -> Result<(), Error> {
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "free") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(handle.offset as i64)], &mut [])?;
+        let (linker, store) = self.linker_and_store();
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "free") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(handle.offset as i64)], &mut [])
+                    .context("failed to free extism memory")
+            )?;
         } else {
             anyhow::bail!("unable to locate an extism kernel function: free",)
         }
@@ -250,12 +272,16 @@ impl CurrentPlugin {
     }
 
     pub fn memory_length(&mut self, offs: u64) -> Result<u64, Error> {
-        let (linker, mut store) = self.linker_and_store();
+        let (linker, store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "length") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(offs as i64)], output)?;
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "length") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(offs as i64)], output)
+                    .context("failed to get length of extism memory handle")
+            )?;
         } else {
             anyhow::bail!("unable to locate an extism kernel function: length",)
         }
@@ -270,12 +296,16 @@ impl CurrentPlugin {
     }
 
     pub fn memory_length_unsafe(&mut self, offs: u64) -> Result<u64, Error> {
-        let (linker, mut store) = self.linker_and_store();
+        let (linker, store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "length_unsafe") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(offs as i64)], output)?;
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "length_unsafe") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(offs as i64)], output)
+                    .context("failed to get length of extism memory using length_unsafe")
+            )?;
         } else {
             anyhow::bail!("unable to locate an extism kernel function: length_unsafe",)
         }
@@ -308,6 +338,7 @@ impl CurrentPlugin {
         manifest: extism_manifest::Manifest,
         wasi: bool,
         available_pages: Option<u32>,
+        allow_http_response_headers: bool,
         id: uuid::Uuid,
     ) -> Result<Self, Error> {
         let wasi = if wasi {
@@ -351,7 +382,7 @@ impl CurrentPlugin {
 
         let memory_limiter = if let Some(pgs) = available_pages {
             let n = pgs as usize * 65536;
-            Some(crate::current_plugin::MemoryLimiter {
+            Some(MemoryLimiter {
                 max_bytes: n,
                 bytes_left: n,
             })
@@ -370,6 +401,11 @@ impl CurrentPlugin {
             memory_limiter,
             id,
             start_time: std::time::Instant::now(),
+            http_headers: if allow_http_response_headers {
+                Some(BTreeMap::new())
+            } else {
+                None
+            },
         })
     }
 
@@ -414,12 +450,12 @@ impl CurrentPlugin {
     /// Clear the current plugin error
     pub fn clear_error(&mut self) {
         trace!(plugin = self.id.to_string(), "CurrentPlugin::clear_error");
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_set") {
+        let (linker, store) = self.linker_and_store();
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_set") {
             let res = f
                 .into_func()
                 .unwrap()
-                .call(&mut store, &[Val::I64(0)], &mut []);
+                .call(&mut *store, &[Val::I64(0)], &mut []);
             if let Err(e) = res {
                 error!(
                     plugin = self.id.to_string(),
@@ -450,13 +486,15 @@ impl CurrentPlugin {
     pub fn set_error(&mut self, s: impl AsRef<str>) -> Result<(u64, u64), Error> {
         let s = s.as_ref();
         debug!(plugin = self.id.to_string(), "set error: {:?}", s);
-        let handle = self.current_plugin_mut().memory_new(s)?;
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_set") {
-            f.into_func().unwrap().call(
-                &mut store,
-                &[Val::I64(handle.offset() as i64)],
-                &mut [],
+        let handle = self.memory_new(s)?;
+        let (linker, store) = self.linker_and_store();
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_set") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(handle.offset() as i64)], &mut [])
+                    .context("failed to set extism error")
             )?;
             Ok((handle.offset(), s.len() as u64))
         } else {
@@ -465,10 +503,13 @@ impl CurrentPlugin {
     }
 
     pub(crate) fn get_error_position(&mut self) -> (u64, u64) {
-        let (linker, mut store) = self.linker_and_store();
+        let (linker, store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_get") {
-            if let Err(e) = f.into_func().unwrap().call(&mut store, &[], output) {
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_get") {
+            if let Err(e) = catch_out_of_fuel!(
+                &store,
+                f.into_func().unwrap().call(&mut *store, &[], output)
+            ) {
                 error!(
                     plugin = self.id.to_string(),
                     "unable to call extism:host/env::error_get: {:?}", e

runtime/src/lib.rs

@@ -1,6 +1,17 @@
 // Makes proc-macros able to resolve `::extism` correctly
 extern crate self as extism;
 
+macro_rules! catch_out_of_fuel {
+    ($store: expr, $x:expr) => {{
+        let y = $x;
+        if y.is_err() && $store.get_fuel().is_ok_and(|x| x == 0) {
+            Err(Error::msg("plugin ran out of fuel"))
+        } else {
+            y
+        }
+    }};
+}
+
 pub(crate) use extism_convert::*;
 pub(crate) use std::collections::BTreeMap;
 use std::str::FromStr;
@@ -28,7 +39,9 @@ pub use current_plugin::CurrentPlugin;
 pub use extism_convert::{FromBytes, FromBytesOwned, ToBytes};
 pub use extism_manifest::{Manifest, Wasm, WasmMetadata};
 pub use function::{Function, UserData, Val, ValType, PTR};
-pub use plugin::{CancelHandle, Plugin, WasmInput, EXTISM_ENV_MODULE, EXTISM_USER_MODULE};
+pub use plugin::{
+    CancelHandle, CompiledPlugin, Plugin, WasmInput, EXTISM_ENV_MODULE, EXTISM_USER_MODULE,
+};
 pub use plugin_builder::{DebugOptions, PluginBuilder};
 
 pub(crate) use internal::{Internal, Wasi};
@@ -78,11 +91,16 @@ pub fn set_log_callback<F: 'static + Clone + Fn(&str)>(
     filter: impl AsRef<str>,
 ) -> Result<(), Error> {
     let filter = filter.as_ref();
-    let cfg = tracing_subscriber::FmtSubscriber::builder().with_env_filter(
-        tracing_subscriber::EnvFilter::builder()
-            .with_default_directive(tracing::Level::ERROR.into())
-            .parse_lossy(filter),
-    );
+    let is_level = tracing::Level::from_str(filter).is_ok();
+    let cfg = tracing_subscriber::FmtSubscriber::builder().with_env_filter({
+        let x = tracing_subscriber::EnvFilter::builder()
+            .with_default_directive(tracing::Level::ERROR.into());
+        if is_level {
+            x.parse_lossy(format!("extism={}", filter))
+        } else {
+            x.parse_lossy(filter)
+        }
+    });
     let w = LogFunction { func };
     cfg.with_ansi(false)
         .with_writer(move || w.clone())

runtime/src/pdk.rs

@@ -20,6 +20,8 @@ macro_rules! args {
 /// Get a configuration value
 /// Params: i64 (offset)
 /// Returns: i64 (offset)
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn config_get(
     mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -38,6 +40,7 @@ pub(crate) fn config_get(
     };
     let val = data.manifest.config.get(key);
     let ptr = val.map(|x| (x.len(), x.as_ptr()));
+    data.memory_free(handle)?;
     let mem = match ptr {
         Some((len, ptr)) => {
             let bytes = unsafe { std::slice::from_raw_parts(ptr, len) };
@@ -55,6 +58,9 @@ pub(crate) fn config_get(
 /// Get a variable
 /// Params: i64 (offset)
 /// Returns: i64 (offset)
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value, but the return value
+/// will need to be freed
 pub(crate) fn var_get(
     mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -73,6 +79,8 @@ pub(crate) fn var_get(
     };
     let val = data.vars.get(key);
     let ptr = val.map(|x| (x.len(), x.as_ptr()));
+    data.memory_free(handle)?;
+
     let mem = match ptr {
         Some((len, ptr)) => {
             let bytes = unsafe { std::slice::from_raw_parts(ptr, len) };
@@ -90,6 +98,8 @@ pub(crate) fn var_get(
 /// Set a variable, if the value offset is 0 then the provided key will be removed
 /// Params: i64 (key offset), i64 (value offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handles passed in
+/// the caller should not `free` these values
 pub(crate) fn var_set(
     mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -104,12 +114,12 @@ pub(crate) fn var_set(
     let voffset = args!(input, 1, i64) as u64;
     let key_offs = args!(input, 0, i64) as u64;
 
+    let key_handle = match data.memory_handle(key_offs) {
+        Some(h) => h,
+        None => anyhow::bail!("invalid handle offset for var key: {key_offs}"),
+    };
     let key = {
-        let handle = match data.memory_handle(key_offs) {
-            Some(h) => h,
-            None => anyhow::bail!("invalid handle offset for var key: {key_offs}"),
-        };
-        let key = data.memory_str(handle)?;
+        let key = data.memory_str(key_handle)?;
         let key_len = key.len();
         let key_ptr = key.as_ptr();
         unsafe { std::str::from_utf8_unchecked(std::slice::from_raw_parts(key_ptr, key_len)) }
@@ -118,6 +128,7 @@ pub(crate) fn var_set(
     // Remove if the value offset is 0
     if voffset == 0 {
         data.vars.remove(key);
+        data.memory_free(key_handle)?;
         return Ok(());
     }
 
@@ -144,6 +155,9 @@ pub(crate) fn var_set(
 
     let value = data.memory_bytes(handle)?.to_vec();
 
+    data.memory_free(handle)?;
+    data.memory_free(key_handle)?;
+
     // Insert the value from memory into the `vars` map
     data.vars.insert(key.to_string(), value);
 
@@ -153,6 +167,9 @@ pub(crate) fn var_set(
 /// Make an HTTP request
 /// Params: i64 (offset to JSON encoded HttpRequest), i64 (offset to body or 0)
 /// Returns: i64 (offset)
+/// **Note**: this function takes ownership of the handles passed in
+/// the caller should not `free` these values, the result will need to
+/// be freed.
 pub(crate) fn http_request(
     #[allow(unused_mut)] mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -166,6 +183,7 @@ pub(crate) fn http_request(
             Some(h) => h,
             None => anyhow::bail!("http_request input is invalid: {http_req_offset}"),
         };
+        data.memory_free(handle)?;
         let req: extism_manifest::HttpRequest = serde_json::from_slice(data.memory_bytes(handle)?)?;
         output[0] = Val::I64(0);
         anyhow::bail!(
@@ -176,12 +194,16 @@ pub(crate) fn http_request(
 
     #[cfg(feature = "http")]
     {
+        data.http_headers.iter_mut().for_each(|x| x.clear());
+        data.http_status = 0;
+
         use std::io::Read;
         let handle = match data.memory_handle(http_req_offset) {
             Some(h) => h,
             None => anyhow::bail!("invalid handle offset for http request: {http_req_offset}"),
         };
         let req: extism_manifest::HttpRequest = serde_json::from_slice(data.memory_bytes(handle)?)?;
+        data.memory_free(handle)?;
 
         let body_offset = args!(input, 1, i64) as u64;
 
@@ -235,8 +257,19 @@ pub(crate) fn http_request(
             r.call()
         };
 
+        if let Some(handle) = data.memory_handle(body_offset) {
+            data.memory_free(handle)?;
+        }
+
         let reader = match res {
             Ok(res) => {
+                if let Some(headers) = &mut data.http_headers {
+                    for name in res.headers_names() {
+                        if let Some(h) = res.header(&name) {
+                            headers.insert(name, h.to_string());
+                        }
+                    }
+                }
                 data.http_status = res.status();
                 Some(res.into_reader())
             }
@@ -294,6 +327,24 @@ pub(crate) fn http_status_code(
     Ok(())
 }
 
+/// Get the HTTP response headers from the last HTTP request
+/// Params: none
+/// Returns: i64 (offset)
+pub(crate) fn http_headers(
+    mut caller: Caller<CurrentPlugin>,
+    _input: &[Val],
+    output: &mut [Val],
+) -> Result<(), Error> {
+    let data: &mut CurrentPlugin = caller.data_mut();
+    if let Some(h) = &data.http_headers {
+        let headers = serde_json::to_string(h)?;
+        data.memory_set_val(&mut output[0], headers)?;
+    } else {
+        output[0] = Val::I64(0);
+    }
+    Ok(())
+}
+
 pub fn log(
     level: tracing::Level,
     mut caller: Caller<CurrentPlugin>,
@@ -301,13 +352,22 @@ pub fn log(
     _output: &mut [Val],
 ) -> Result<(), Error> {
     let data: &mut CurrentPlugin = caller.data_mut();
+
     let offset = args!(input, 0, i64) as u64;
 
+    // Check if the current log level should be logged
+    let global_log_level = tracing::level_filters::LevelFilter::current();
+    if global_log_level == tracing::level_filters::LevelFilter::OFF || level > global_log_level {
+        if let Some(handle) = data.memory_handle(offset) {
+            data.memory_free(handle)?;
+        }
+        return Ok(());
+    }
+
     let handle = match data.memory_handle(offset) {
         Some(h) => h,
         None => anyhow::bail!("invalid handle offset for log message: {offset}"),
     };
-
     let id = data.id.to_string();
     let buf = data.memory_str(handle);
 
@@ -331,12 +391,16 @@ pub fn log(
         },
         Err(_) => tracing::error!(plugin = id, "unable to log message: {:?}", buf),
     }
+
+    data.memory_free(handle)?;
     Ok(())
 }
 
 /// Write to logs (warning)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_warn(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -348,6 +412,8 @@ pub(crate) fn log_warn(
 /// Write to logs (info)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_info(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -359,6 +425,8 @@ pub(crate) fn log_info(
 /// Write to logs (debug)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_debug(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -370,6 +438,8 @@ pub(crate) fn log_debug(
 /// Write to logs (error)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_error(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -377,3 +447,46 @@ pub(crate) fn log_error(
 ) -> Result<(), Error> {
     log(tracing::Level::ERROR, caller, input, _output)
 }
+
+/// Write to logs (trace)
+/// Params: i64 (offset)
+/// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
+pub(crate) fn log_trace(
+    caller: Caller<CurrentPlugin>,
+    input: &[Val],
+    _output: &mut [Val],
+) -> Result<(), Error> {
+    log(tracing::Level::TRACE, caller, input, _output)
+}
+
+/// Get the log level
+/// Params: none
+/// Returns: i32 (log level)
+pub(crate) fn get_log_level(
+    mut _caller: Caller<CurrentPlugin>,
+    _input: &[Val],
+    output: &mut [Val],
+) -> Result<(), Error> {
+    let level = tracing::level_filters::LevelFilter::current();
+    if level == tracing::level_filters::LevelFilter::OFF {
+        output[0] = Val::I32(i32::MAX)
+    } else {
+        output[0] = Val::I32(log_level_to_int(
+            level.into_level().unwrap_or(tracing::Level::ERROR),
+        ));
+    }
+    Ok(())
+}
+
+/// Convert log level to integer
+pub(crate) const fn log_level_to_int(level: tracing::Level) -> i32 {
+    match level {
+        tracing::Level::TRACE => 0,
+        tracing::Level::DEBUG => 1,
+        tracing::Level::INFO => 2,
+        tracing::Level::WARN => 3,
+        tracing::Level::ERROR => 4,
+    }
+}

runtime/src/plugin.rs

@@ -1,9 +1,11 @@
 use std::{
     any::Any,
     collections::{BTreeMap, BTreeSet},
-    path::PathBuf,
 };
 
+use anyhow::Context;
+use plugin_builder::PluginBuilderOptions;
+
 use crate::*;
 
 pub const EXTISM_ENV_MODULE: &str = "extism:host/env";
@@ -36,6 +38,66 @@ impl CancelHandle {
     }
 }
 
+#[derive(Clone)]
+pub struct CompiledPlugin {
+    pub(crate) manifest: Manifest,
+    pub(crate) modules: BTreeMap<String, Module>,
+    pub(crate) options: PluginBuilderOptions,
+    pub(crate) engine: wasmtime::Engine,
+}
+
+impl CompiledPlugin {
+    /// Create a new pre-compiled plugin
+    pub fn new(builder: PluginBuilder) -> Result<CompiledPlugin, Error> {
+        let mut config = builder.config.unwrap_or_default();
+        config
+            .async_support(false)
+            .epoch_interruption(true)
+            .debug_info(builder.options.debug_options.debug_info)
+            .coredump_on_trap(builder.options.debug_options.coredump.is_some())
+            .profiler(builder.options.debug_options.profiling_strategy)
+            .wasm_tail_call(true)
+            .wasm_function_references(true)
+            .wasm_gc(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()?;
+                }
+            }
+        }
+
+        let engine = Engine::new(&config)?;
+
+        let (manifest, modules) = manifest::load(&engine, builder.source)?;
+        if modules.len() <= 1 {
+            anyhow::bail!("No wasm modules provided");
+        } else if !modules.contains_key(MAIN_KEY) {
+            anyhow::bail!("No main module provided");
+        }
+
+        Ok(CompiledPlugin {
+            manifest,
+            modules,
+            options: builder.options,
+            engine,
+        })
+    }
+}
+
 /// Plugin contains everything needed to execute a WASM function
 pub struct Plugin {
     /// A unique ID for each plugin
@@ -83,6 +145,10 @@ pub struct Plugin {
     pub(crate) debug_options: DebugOptions,
 
     pub(crate) error_msg: Option<Vec<u8>>,
+
+    pub(crate) fuel: Option<u64>,
+
+    pub(crate) host_context: Rooted<ExternRef>,
 }
 
 unsafe impl Send for Plugin {}
@@ -133,7 +199,7 @@ pub enum WasmInput<'a> {
     ManifestRef(&'a Manifest),
 }
 
-impl<'a> From<Manifest> for WasmInput<'a> {
+impl From<Manifest> for WasmInput<'_> {
     fn from(value: Manifest) -> Self {
         WasmInput::Manifest(value)
     }
@@ -163,7 +229,7 @@ impl<'a> From<&'a str> for WasmInput<'a> {
     }
 }
 
-impl<'a> From<Vec<u8>> for WasmInput<'a> {
+impl From<Vec<u8>> for WasmInput<'_> {
     fn from(value: Vec<u8>) -> Self {
         WasmInput::Data(value.into())
     }
@@ -214,14 +280,24 @@ fn add_module<T: 'static>(
     Ok(())
 }
 
+#[allow(clippy::type_complexity)]
 fn relink(
     engine: &Engine,
     mut store: &mut Store<CurrentPlugin>,
     imports: &[Function],
     modules: &BTreeMap<String, Module>,
     with_wasi: bool,
-) -> Result<(InstancePre<CurrentPlugin>, Linker<CurrentPlugin>), Error> {
+) -> Result<
+    (
+        InstancePre<CurrentPlugin>,
+        Linker<CurrentPlugin>,
+        Rooted<ExternRef>,
+    ),
+    Error,
+> {
     let mut linker = Linker::new(engine);
+    linker.allow_shadowing(true);
+
     // Define PDK functions
     macro_rules! add_funcs {
             ($($name:ident($($args:expr),*) $(-> $($r:expr),*)?);* $(;)?) => {
@@ -240,12 +316,45 @@ fn relink(
         var_set(I64, I64);
         http_request(I64, I64) -> I64;
         http_status_code() -> I32;
+        http_headers() -> I64;
         log_warn(I64);
         log_info(I64);
         log_debug(I64);
         log_error(I64);
+        log_trace(I64);
+        get_log_level() -> I32;
     );
 
+    for (name, module) in modules.iter() {
+        if name == EXTISM_ENV_MODULE {
+            continue;
+        }
+
+        for import in module.imports() {
+            if import.module() == EXTISM_ENV_MODULE
+                && modules[EXTISM_ENV_MODULE]
+                    .get_export(import.name())
+                    .is_none()
+                && linker
+                    .get(&mut store, EXTISM_ENV_MODULE, import.name())
+                    .is_none()
+            {
+                let (kind, ty) = match import.ty() {
+                    ExternType::Func(t) => ("function", t.to_string()),
+                    ExternType::Global(t) => ("global", t.content().to_string()),
+                    ExternType::Table(t) => ("table", t.element().to_string()),
+                    ExternType::Memory(_) => ("memory", String::new()),
+                };
+                anyhow::bail!(
+                    "Invalid {kind} import from extism:host/env: {} {ty}\n\n\
+                    Note: This may indicate that the PDK that was used to build this plugin has additional features that aren't \
+                    available in this version of the SDK, try updating the SDK to the latest version.",
+                    import.name(),
+                )
+            }
+        }
+    }
+
     let mut linked = BTreeSet::new();
     linker.module(&mut store, EXTISM_ENV_MODULE, &modules[EXTISM_ENV_MODULE])?;
     linked.insert(EXTISM_ENV_MODULE.to_string());
@@ -276,9 +385,12 @@ fn relink(
         )?;
     }
 
+    let inner: Box<dyn std::any::Any + Send + Sync> = Box::new(());
+    let host_context = ExternRef::new(store, inner)?;
+
     let main = &modules[MAIN_KEY];
     let instance_pre = linker.instantiate_pre(main)?;
-    Ok((instance_pre, linker))
+    Ok((instance_pre, linker, host_context))
 }
 
 impl Plugin {
@@ -289,67 +401,45 @@ impl Plugin {
         imports: impl IntoIterator<Item = Function>,
         with_wasi: bool,
     ) -> Result<Plugin, Error> {
-        Self::build_new(wasm.into(), imports, with_wasi, Default::default(), None)
+        Self::new_from_compiled(&CompiledPlugin::new(
+            PluginBuilder::new(wasm)
+                .with_functions(imports)
+                .with_wasi(with_wasi),
+        )?)
     }
 
-    pub(crate) fn build_new(
-        wasm: WasmInput<'_>,
-        imports: impl IntoIterator<Item = Function>,
-        with_wasi: bool,
-        debug_options: DebugOptions,
-        cache_dir: Option<Option<PathBuf>>,
-    ) -> Result<Plugin, Error> {
-        // Setup wasmtime types
-        let mut config = Config::new();
-        config
-            .epoch_interruption(true)
-            .debug_info(debug_options.debug_info)
-            .coredump_on_trap(debug_options.coredump.is_some())
-            .profiler(debug_options.profiling_strategy)
-            .wasm_tail_call(true)
-            .wasm_function_references(true)
-            .wasm_gc(true);
-
-        match cache_dir {
-            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()?;
-                }
-            }
-        }
-
-        let engine = Engine::new(&config)?;
-        let (manifest, modules) = manifest::load(&engine, wasm)?;
-        if modules.len() <= 1 {
-            anyhow::bail!("No wasm modules provided");
-        } else if !modules.contains_key(MAIN_KEY) {
-            anyhow::bail!("No main module provided");
-        }
-
-        let available_pages = manifest.memory.max_pages;
+    /// Create a new plugin from a pre-compiled plugin
+    pub fn new_from_compiled(compiled: &CompiledPlugin) -> Result<Plugin, Error> {
+        let available_pages = compiled.manifest.memory.max_pages;
         debug!("Available pages: {available_pages:?}");
 
         let id = uuid::Uuid::new_v4();
         let mut store = Store::new(
-            &engine,
-            CurrentPlugin::new(manifest, with_wasi, available_pages, id)?,
+            &compiled.engine,
+            CurrentPlugin::new(
+                compiled.manifest.clone(),
+                compiled.options.wasi,
+                available_pages,
+                compiled.options.http_response_headers,
+                id,
+            )?,
         );
         store.set_epoch_deadline(1);
+        if let Some(fuel) = compiled.options.fuel {
+            store.set_fuel(fuel)?;
+        }
 
-        let imports: Vec<Function> = imports.into_iter().collect();
-        let (instance_pre, linker) = relink(&engine, &mut store, &imports, &modules, with_wasi)?;
-
+        let imports: Vec<Function> = compiled.options.functions.to_vec();
+        let (instance_pre, linker, host_context) = relink(
+            &compiled.engine,
+            &mut store,
+            &imports,
+            &compiled.modules,
+            compiled.options.wasi,
+        )?;
         let timer_tx = Timer::tx();
         let mut plugin = Plugin {
-            modules,
+            modules: compiled.modules.clone(),
             linker,
             instance: std::sync::Arc::new(std::sync::Mutex::new(None)),
             instance_pre,
@@ -361,9 +451,11 @@ impl Plugin {
             instantiations: 0,
             output: Output::default(),
             store_needs_reset: false,
-            debug_options,
+            debug_options: compiled.options.debug_options.clone(),
             _functions: imports,
             error_msg: None,
+            fuel: compiled.options.fuel,
+            host_context,
         };
 
         plugin.current_plugin_mut().store = &mut plugin.store;
@@ -392,12 +484,17 @@ impl Plugin {
                     internal.manifest.clone(),
                     internal.wasi.is_some(),
                     internal.available_pages,
+                    internal.http_headers.is_some(),
                     self.id,
                 )?,
             );
             self.store.set_epoch_deadline(1);
 
-            let (instance_pre, linker) = relink(
+            if let Some(fuel) = self.fuel {
+                self.store.set_fuel(fuel)?;
+            }
+
+            let (instance_pre, linker, host_context) = relink(
                 &engine,
                 &mut self.store,
                 &self._functions,
@@ -406,6 +503,7 @@ impl Plugin {
             )?;
             self.linker = linker;
             self.instance_pre = instance_pre;
+            self.host_context = host_context;
             let store = &mut self.store as *mut _;
             let linker = &mut self.linker as *mut _;
             let current_plugin = self.current_plugin_mut();
@@ -462,7 +560,7 @@ impl Plugin {
     }
 
     /// Returns `true` if the given function exists, otherwise `false`
-    pub fn function_exists(&mut self, function: impl AsRef<str>) -> bool {
+    pub fn function_exists(&self, function: impl AsRef<str>) -> bool {
         self.modules[MAIN_KEY]
             .get_export(function.as_ref())
             .map(|x| {
@@ -513,10 +611,16 @@ impl Plugin {
             .linker
             .get(&mut self.store, EXTISM_ENV_MODULE, "input_set")
         {
-            f.into_func().unwrap().call(
-                &mut self.store,
-                &[Val::I64(handle.offset() as i64), Val::I64(len as i64)],
-                &mut [],
+            catch_out_of_fuel!(
+                &self.store,
+                f.into_func()
+                    .unwrap()
+                    .call(
+                        &mut self.store,
+                        &[Val::I64(handle.offset() as i64), Val::I64(len as i64)],
+                        &mut [],
+                    )
+                    .context("unable to set extism input")
             )?;
         }
 
@@ -524,7 +628,8 @@ impl Plugin {
             self.linker
                 .get(&mut self.store, EXTISM_ENV_MODULE, "extism_context")
         {
-            ctxt.set(&mut self.store, Val::ExternRef(host_context))?;
+            ctxt.set(&mut self.store, Val::ExternRef(host_context))
+                .context("unable to set extism host context")?;
         }
 
         Ok(())
@@ -535,7 +640,13 @@ impl Plugin {
         let id = self.id.to_string();
 
         if let Some(f) = self.linker.get(&mut self.store, EXTISM_ENV_MODULE, "reset") {
-            f.into_func().unwrap().call(&mut self.store, &[], &mut [])?;
+            catch_out_of_fuel!(
+                &self.store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut self.store, &[], &mut [])
+                    .context("extism reset failed")
+            )?;
         } else {
             error!(plugin = &id, "call to extism:host/env::reset failed");
         }
@@ -611,19 +722,28 @@ impl Plugin {
 
     // Initialize the guest runtime
     pub(crate) fn initialize_guest_runtime(&mut self) -> Result<(), Error> {
-        let mut store = &mut self.store;
+        let store = &mut self.store;
         if let Some(runtime) = &self.runtime {
             trace!(plugin = self.id.to_string(), "Plugin::initialize_runtime");
             match runtime {
                 GuestRuntime::Haskell { init, reactor_init } => {
                     if let Some(reactor_init) = reactor_init {
-                        reactor_init.call(&mut store, &[], &mut [])?;
+                        catch_out_of_fuel!(
+                            &store,
+                            reactor_init
+                                .call(&mut *store, &[], &mut [])
+                                .context("failed to initialize Haskell reactor runtime")
+                        )?;
                     }
-                    let mut results = vec![Val::I32(0); init.ty(&store).results().len()];
-                    init.call(
-                        &mut store,
-                        &[Val::I32(0), Val::I32(0)],
-                        results.as_mut_slice(),
+                    let mut results = vec![Val::I32(0); init.ty(&*store).results().len()];
+                    catch_out_of_fuel!(
+                        &store,
+                        init.call(
+                            &mut *store,
+                            &[Val::I32(0), Val::I32(0)],
+                            results.as_mut_slice(),
+                        )
+                        .context("failed to initialize Haskell using hs_init")
                     )?;
                     debug!(
                         plugin = self.id.to_string(),
@@ -631,7 +751,11 @@ impl Plugin {
                     );
                 }
                 GuestRuntime::Wasi { init } => {
-                    init.call(&mut store, &[], &mut [])?;
+                    catch_out_of_fuel!(
+                        &store,
+                        init.call(&mut *store, &[], &mut [])
+                            .context("failed to initialize wasi runtime")
+                    )?;
                     debug!(plugin = self.id.to_string(), "initialied WASI runtime");
                 }
             }
@@ -644,20 +768,32 @@ impl Plugin {
     fn output_memory_position(&mut self) -> Result<(u64, u64), Error> {
         let out = &mut [Val::I64(0)];
         let out_len = &mut [Val::I64(0)];
-        let mut store = &mut self.store;
+        let store = &mut self.store;
         if let Some(f) = self
             .linker
-            .get(&mut store, EXTISM_ENV_MODULE, "output_offset")
+            .get(&mut *store, EXTISM_ENV_MODULE, "output_offset")
         {
-            f.into_func().unwrap().call(&mut store, &[], out)?;
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[], out)
+                    .context("call to set extism output offset failed")
+            )?;
         } else {
             anyhow::bail!("unable to set output")
         }
         if let Some(f) = self
             .linker
-            .get(&mut store, EXTISM_ENV_MODULE, "output_length")
+            .get(&mut *store, EXTISM_ENV_MODULE, "output_length")
         {
-            f.into_func().unwrap().call(&mut store, &[], out_len)?;
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[], out_len)
+                    .context("call to set extism output length failed")
+            )?;
         } else {
             anyhow::bail!("unable to set output length")
         }
@@ -671,10 +807,10 @@ impl Plugin {
     fn output<'a, T: FromBytes<'a>>(&'a mut self) -> Result<T, Error> {
         let offs = self.output.offset;
         let len = self.output.length;
-        T::from_bytes(
-            self.current_plugin_mut()
-                .memory_bytes(unsafe { MemoryHandle::new(offs, len) })?,
-        )
+        let x = self
+            .current_plugin_mut()
+            .memory_bytes(unsafe { MemoryHandle::new(offs, len) })?;
+        T::from_bytes(x)
     }
 
     // Cache output memory and error information after call is complete
@@ -699,26 +835,40 @@ impl Plugin {
 
     // Implements the build of the `call` function, `raw_call` is also used in the SDK
     // code
-    pub(crate) fn raw_call(
+    pub(crate) fn raw_call<T: 'static + Send + Sync>(
         &mut self,
         lock: &mut std::sync::MutexGuard<Option<Instance>>,
         name: impl AsRef<str>,
         input: impl AsRef<[u8]>,
-        host_context: Option<Rooted<ExternRef>>,
+        host_context: Option<T>,
     ) -> Result<i32, (Error, i32)> {
         let name = name.as_ref();
         let input = input.as_ref();
 
-        if let Err(e) = self.reset_store(lock) {
-            error!(
-                plugin = self.id.to_string(),
-                "call to Plugin::reset_store failed: {e:?}"
-            );
+        if let Some(fuel) = self.fuel {
+            self.store.set_fuel(fuel).map_err(|x| (x, -1))?;
         }
 
+        catch_out_of_fuel!(&self.store, self.reset_store(lock)).map_err(|x| (x, -1))?;
+
         self.instantiate(lock).map_err(|e| (e, -1))?;
 
-        self.set_input(input.as_ptr(), input.len(), host_context)
+        // Set host context
+        let r = if let Some(host_context) = host_context {
+            let inner = self
+                .host_context
+                .data_mut(&mut self.store)
+                .map_err(|x| (x, -1))?;
+            if let Some(inner) = inner.downcast_mut::<Box<dyn std::any::Any + Send + Sync>>() {
+                let x: Box<T> = Box::new(host_context);
+                *inner = x;
+            }
+            Some(self.host_context)
+        } else {
+            None
+        };
+
+        self.set_input(input.as_ptr(), input.len(), r)
             .map_err(|x| (x, -1))?;
 
         let func = match self.get_func(lock, name) {
@@ -755,40 +905,70 @@ impl Plugin {
         let mut results = vec![wasmtime::Val::I32(0); n_results];
         let mut res = func.call(self.store_mut(), &[], results.as_mut_slice());
 
+        // Reset host context
+        if let Ok(inner) = self.host_context.data_mut(&mut self.store) {
+            if let Some(inner) = inner.downcast_mut::<Box<dyn std::any::Any + Send + Sync>>() {
+                let x: Box<dyn Any + Send + Sync> = Box::new(());
+                *inner = x;
+            }
+        }
+
         // Stop timer
         self.store
             .epoch_deadline_callback(|_| Ok(UpdateDeadline::Continue(1)));
         let _ = self.timer_tx.send(TimerAction::Stop { id: self.id });
         self.store_needs_reset = name == "_start";
 
-        // Get extism error
-        self.get_output_after_call().map_err(|x| (x, -1))?;
-        let mut rc = 0;
-        if !results.is_empty() {
-            rc = results[0].i32().unwrap_or(-1);
-            debug!(plugin = self.id.to_string(), "got return code: {}", rc);
-        }
+        let mut rc = -1;
+        if self.store.get_fuel().is_ok_and(|x| x == 0) {
+            res = Err(Error::msg("plugin ran out of fuel"));
+        } else {
+            // Get extism error
+            let output_res = self.get_output_after_call().map_err(|x| (x, -1));
 
-        if self.output.error_offset != 0 && self.output.error_length != 0 {
-            let handle = MemoryHandle {
-                offset: self.output.error_offset,
-                length: self.output.error_length,
-            };
-            if let Ok(e) = self.current_plugin_mut().memory_str(handle) {
-                let x = e.to_string();
-                error!(
-                    plugin = self.id.to_string(),
-                    "call to {name} returned with error message: {}", x
-                );
-                if let Err(e) = res {
-                    res = Err(Error::msg(x).context(e));
-                } else {
-                    res = Err(Error::msg(x))
+            // Get the return code
+            if output_res.is_ok() && res.is_ok() {
+                rc = 0;
+                if !results.is_empty() {
+                    rc = results[0].i32().unwrap_or(-1);
+                    debug!(plugin = self.id.to_string(), "got return code: {}", rc);
                 }
+            }
+
+            // on extism error
+            if output_res.is_ok() && self.extism_error_is_set() {
+                let handle = MemoryHandle {
+                    offset: self.output.error_offset,
+                    length: self.output.error_length,
+                };
+                match self.current_plugin_mut().memory_str(handle) {
+                    Ok(e) => {
+                        let x = e.to_string();
+                        error!(
+                            plugin = self.id.to_string(),
+                            "call to {name} returned with error message: {}", x
+                        );
+                        if let Err(e) = res {
+                            res = Err(Error::msg(x).context(e));
+                        } else {
+                            res = Err(Error::msg(x))
+                        }
+                    }
+                    Err(msg) => {
+                        res = Err(Error::msg(format!(
+                            "unable to load error message from memory: {}",
+                            msg,
+                        )));
+                    }
+                }
+            // on wasmtime error
+            } else if let Err(e) = &res {
+                if e.is::<wasmtime::Trap>() {
+                    rc = 134; // EXIT_SIGNALED_SIGABRT
+                }
+            // if there was an error retrieving the output
             } else {
-                res = Err(Error::msg(format!(
-                    "Call to Extism plugin function {name} encountered an error"
-                )));
+                output_res?;
             }
         }
 
@@ -843,11 +1023,12 @@ impl Plugin {
                         plugin = self.id.to_string(),
                         "WASI exit code: {}", exit_code
                     );
-                    if exit_code == 0 {
+
+                    if exit_code == 0 && !self.extism_error_is_set() {
                         return Ok(0);
                     }
 
-                    return Err((e.context("WASI exit code"), exit_code));
+                    return Err((e, exit_code));
                 }
 
                 // Handle timeout interrupts
@@ -875,6 +1056,10 @@ impl Plugin {
         }
     }
 
+    fn extism_error_is_set(&self) -> bool {
+        self.output.error_offset != 0 && self.output.error_length != 0
+    }
+
     /// Call a function by name with the given input, the return value is
     /// the output data returned by the plugin. The return type can be anything that implements
     /// [FromBytes]. This data will be invalidated next time the plugin is called.
@@ -900,7 +1085,7 @@ impl Plugin {
         let lock = self.instance.clone();
         let mut lock = lock.lock().unwrap();
         let data = input.to_bytes()?;
-        self.raw_call(&mut lock, name, data, None)
+        self.raw_call(&mut lock, name, data, None::<()>)
             .map_err(|e| e.0)
             .and_then(move |rc| {
                 if rc != 0 {
@@ -925,8 +1110,7 @@ impl Plugin {
         let lock = self.instance.clone();
         let mut lock = lock.lock().unwrap();
         let data = input.to_bytes()?;
-        let ctx = ExternRef::new(&mut self.store, host_context)?;
-        self.raw_call(&mut lock, name, data, Some(ctx))
+        self.raw_call(&mut lock, name, data, Some(host_context))
             .map_err(|e| e.0)
             .and_then(move |_| self.output())
     }
@@ -945,7 +1129,7 @@ impl Plugin {
         let lock = self.instance.clone();
         let mut lock = lock.lock().unwrap();
         let data = input.to_bytes().map_err(|e| (e, -1))?;
-        self.raw_call(&mut lock, name, data, None)
+        self.raw_call(&mut lock, name, data, None::<()>)
             .and_then(move |_| self.output().map_err(|e| (e, -1)))
     }
 
@@ -956,41 +1140,39 @@ impl Plugin {
 
     pub(crate) fn clear_error(&mut self) -> Result<(), Error> {
         trace!(plugin = self.id.to_string(), "clearing error");
+        self.error_msg = None;
         let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_set") {
-            f.into_func()
+        #[allow(clippy::needless_borrows_for_generic_args)]
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_set") {
+            let x = f
+                .into_func()
                 .unwrap()
-                .call(&mut store, &[Val::I64(0)], &mut [])?;
+                .call(&mut store, &[Val::I64(0)], &mut [])
+                .context("unable to clear error message");
+            catch_out_of_fuel!(&store, x)?;
             Ok(())
         } else {
             anyhow::bail!("Plugin::clear_error failed, extism:host/env::error_set not found")
         }
     }
 
-    // A convenience method to set the plugin error and return a value
-    pub(crate) fn return_error<E>(
-        &mut self,
-        instance_lock: &mut std::sync::MutexGuard<Option<Instance>>,
-        e: impl std::fmt::Display,
-        x: E,
-    ) -> E {
-        if instance_lock.is_none() {
-            error!(
-                plugin = self.id.to_string(),
-                "no instance, unable to set error: {}", e
-            );
-            return x;
-        }
-        match self.current_plugin_mut().set_error(e.to_string()) {
-            Ok((a, b)) => {
-                self.output.error_offset = a;
-                self.output.error_length = b;
-            }
-            Err(e) => {
-                error!(plugin = self.id.to_string(), "unable to set error: {e:?}")
-            }
-        }
-        x
+    /// Returns the amount of fuel consumed by the plugin.
+    ///
+    /// This function calculates the difference between the initial fuel and the remaining fuel.
+    /// If either the initial fuel or the remaining fuel is not set, it returns `None`.
+    ///
+    /// # Returns
+    ///
+    /// * `Some(u64)` - The amount of fuel consumed.
+    /// * `None` - If the initial fuel or remaining fuel is not set.
+    pub fn fuel_consumed(&self) -> Option<u64> {
+        self.fuel.map(|x| {
+            x.saturating_sub(
+                self.store
+                    .get_fuel()
+                    .expect("fuel support should be enabled to use fuel"),
+            )
+        })
     }
 }
 
@@ -1035,7 +1217,7 @@ macro_rules! typed_plugin {
 
         impl TryFrom<$crate::Plugin> for $name {
             type Error = $crate::Error;
-            fn try_from(mut x: $crate::Plugin) -> Result<Self, Self::Error> {
+            fn try_from(x: $crate::Plugin) -> Result<Self, Self::Error> {
                 $(
                     if !x.function_exists(stringify!($f)) {
                         return Err($crate::Error::msg(format!("Invalid function: {}", stringify!($f))));

runtime/src/plugin_builder.rs

@@ -34,11 +34,19 @@ impl Default for DebugOptions {
 
 /// PluginBuilder is used to configure and create `Plugin` instances
 pub struct PluginBuilder<'a> {
-    source: WasmInput<'a>,
-    wasi: bool,
-    functions: Vec<Function>,
-    debug_options: DebugOptions,
-    cache_config: Option<Option<PathBuf>>,
+    pub(crate) source: WasmInput<'a>,
+    pub(crate) config: Option<wasmtime::Config>,
+    pub(crate) options: PluginBuilderOptions,
+}
+
+#[derive(Clone)]
+pub(crate) struct PluginBuilderOptions {
+    pub(crate) wasi: bool,
+    pub(crate) functions: Vec<Function>,
+    pub(crate) debug_options: DebugOptions,
+    pub(crate) cache_config: Option<Option<PathBuf>>,
+    pub(crate) fuel: Option<u64>,
+    pub(crate) http_response_headers: bool,
 }
 
 impl<'a> PluginBuilder<'a> {
@@ -46,16 +54,21 @@ impl<'a> PluginBuilder<'a> {
     pub fn new(plugin: impl Into<WasmInput<'a>>) -> Self {
         PluginBuilder {
             source: plugin.into(),
-            wasi: false,
-            functions: vec![],
-            debug_options: DebugOptions::default(),
-            cache_config: None,
+            config: None,
+            options: PluginBuilderOptions {
+                wasi: false,
+                functions: vec![],
+                debug_options: DebugOptions::default(),
+                cache_config: None,
+                fuel: None,
+                http_response_headers: false,
+            },
         }
     }
 
     /// Enables WASI if the argument is set to `true`
     pub fn with_wasi(mut self, wasi: bool) -> Self {
-        self.wasi = wasi;
+        self.options.wasi = wasi;
         self
     }
 
@@ -74,7 +87,8 @@ impl<'a> PluginBuilder<'a> {
             + Sync
             + Send,
     {
-        self.functions
+        self.options
+            .functions
             .push(Function::new(name, args, returns, user_data, f));
         self
     }
@@ -95,67 +109,97 @@ impl<'a> PluginBuilder<'a> {
             + Sync
             + Send,
     {
-        self.functions
+        self.options
+            .functions
             .push(Function::new(name, args, returns, user_data, f).with_namespace(namespace));
         self
     }
 
     /// Add multiple host functions
     pub fn with_functions(mut self, f: impl IntoIterator<Item = Function>) -> Self {
-        self.functions.extend(f);
+        self.options.functions.extend(f);
         self
     }
 
     /// Set profiling strategy
     pub fn with_profiling_strategy(mut self, p: wasmtime::ProfilingStrategy) -> Self {
-        self.debug_options.profiling_strategy = p;
+        self.options.debug_options.profiling_strategy = p;
         self
     }
 
     /// Enable Wasmtime coredump on trap
     pub fn with_coredump(mut self, path: impl Into<std::path::PathBuf>) -> Self {
-        self.debug_options.coredump = Some(path.into());
+        self.options.debug_options.coredump = Some(path.into());
         self
     }
 
     /// Enable Extism memory dump when plugin calls return an error
     pub fn with_memdump(mut self, path: impl Into<std::path::PathBuf>) -> Self {
-        self.debug_options.memdump = Some(path.into());
+        self.options.debug_options.memdump = Some(path.into());
         self
     }
 
     /// Compile with debug info
     pub fn with_debug_info(mut self) -> Self {
-        self.debug_options.debug_info = true;
+        self.options.debug_options.debug_info = true;
         self
     }
 
     /// Configure debug options
     pub fn with_debug_options(mut self, options: DebugOptions) -> Self {
-        self.debug_options = options;
+        self.options.debug_options = options;
         self
     }
 
     /// Set wasmtime compilation cache config path
     pub fn with_cache_config(mut self, dir: impl Into<PathBuf>) -> Self {
-        self.cache_config = Some(Some(dir.into()));
+        self.options.cache_config = Some(Some(dir.into()));
         self
     }
 
     /// Turn wasmtime compilation caching off
     pub fn with_cache_disabled(mut self) -> Self {
-        self.cache_config = Some(None);
+        self.options.cache_config = Some(None);
+        self
+    }
+
+    /// Limit the number of instructions that can be executed
+    pub fn with_fuel_limit(mut self, fuel: u64) -> Self {
+        self.options.fuel = Some(fuel);
+        self
+    }
+
+    /// Configure an initial wasmtime config to be passed to the plugin
+    ///
+    /// **Warning**: some values might be overwritten by the Extism runtime. In particular:
+    /// - async_support
+    /// - epoch_interruption
+    /// - debug_info
+    /// - coredump_on_trap
+    /// - profiler
+    /// - wasm_tail_call
+    /// - wasm_function_references
+    /// - wasm_gc
+    ///
+    /// See the implementation details of [PluginBuilder::build] and [Plugin::build_new] to verify which values are overwritten.
+    pub fn with_wasmtime_config(mut self, config: wasmtime::Config) -> Self {
+        self.config = Some(config);
+        self
+    }
+
+    /// Enables `http_response_headers`, which allows for plugins to access response headers when using `extism:host/env::http_request`
+    pub fn with_http_response_headers(mut self, allow: bool) -> Self {
+        self.options.http_response_headers = allow;
         self
     }
 
     /// Generate a new plugin with the configured settings
     pub fn build(self) -> Result<Plugin, Error> {
-        Plugin::build_new(
-            self.source,
-            self.functions,
-            self.wasi,
-            self.debug_options,
-            self.cache_config,
-        )
+        Plugin::new_from_compiled(&CompiledPlugin::new(self)?)
+    }
+
+    /// Build new `CompiledPlugin`
+    pub fn compile(self) -> Result<CompiledPlugin, Error> {
+        CompiledPlugin::new(self)
     }
 }

runtime/src/sdk.rs

@@ -1,6 +1,6 @@
 #![allow(clippy::missing_safety_doc)]
 
-use std::os::raw::c_char;
+use std::{os::raw::c_char, ptr::null_mut};
 
 use crate::*;
 
@@ -11,6 +11,12 @@ pub struct ExtismFunction(std::cell::Cell<Option<Function>>);
 /// The return code used to specify a successful plugin call
 pub static EXTISM_SUCCESS: i32 = 0;
 
+fn make_error_msg(s: String) -> Vec<u8> {
+    let mut s = s.into_bytes();
+    s.push(0);
+    s
+}
+
 /// A union type for host function argument/return values
 #[repr(C)]
 pub union ValUnion {
@@ -42,32 +48,32 @@ pub type ExtismFunctionType = extern "C" fn(
 pub type ExtismLogDrainFunctionType = extern "C" fn(data: *const std::ffi::c_char, size: Size);
 
 impl ExtismVal {
-    fn from_val(value: &wasmtime::Val, ctx: impl AsContext) -> Self {
-        match value.ty(ctx) {
-            wasmtime::ValType::I32 => ExtismVal {
+    fn from_val(value: &wasmtime::Val, ctx: impl AsContext) -> Result<Self, Error> {
+        match value.ty(ctx)? {
+            wasmtime::ValType::I32 => Ok(ExtismVal {
                 t: ValType::I32,
                 v: ValUnion {
                     i32: value.unwrap_i32(),
                 },
-            },
-            wasmtime::ValType::I64 => ExtismVal {
+            }),
+            wasmtime::ValType::I64 => Ok(ExtismVal {
                 t: ValType::I64,
                 v: ValUnion {
                     i64: value.unwrap_i64(),
                 },
-            },
-            wasmtime::ValType::F32 => ExtismVal {
+            }),
+            wasmtime::ValType::F32 => Ok(ExtismVal {
                 t: ValType::F32,
                 v: ValUnion {
                     f32: value.unwrap_f32(),
                 },
-            },
-            wasmtime::ValType::F64 => ExtismVal {
+            }),
+            wasmtime::ValType::F64 => Ok(ExtismVal {
                 t: ValType::F64,
                 v: ValUnion {
                     f64: value.unwrap_f64(),
                 },
-            },
+            }),
             t => todo!("{}", t),
         }
     }
@@ -96,7 +102,7 @@ pub unsafe extern "C" fn extism_current_plugin_host_context(
 
     let plugin = &mut *plugin;
     if let Ok(CVoidContainer(ptr)) = plugin.host_context::<CVoidContainer>() {
-        ptr
+        *ptr
     } else {
         std::ptr::null_mut()
     }
@@ -221,7 +227,7 @@ pub unsafe extern "C" fn extism_function_new(
             let store = &*plugin.store;
             let inputs: Vec<_> = inputs
                 .iter()
-                .map(|x| ExtismVal::from_val(x, store))
+                .map(|x| ExtismVal::from_val(x, store).unwrap())
                 .collect();
             let mut output_tmp: Vec<_> = output_types
                 .iter()
@@ -231,12 +237,28 @@ pub unsafe extern "C" fn extism_function_new(
                 })
                 .collect();
 
+            // We cannot simply "get" the Vec's storage pointer because
+            // the underlying storage might be invalid when the Vec is empty.
+            // In that case, we return (null, 0).
+
+            let (inputs_ptr, inputs_len) = if inputs.is_empty() {
+                (core::ptr::null(), 0 as Size)
+            } else {
+                (inputs.as_ptr(), inputs.len() as Size)
+            };
+
+            let (output_ptr, output_len) = if output_tmp.is_empty() {
+                (null_mut(), 0 as Size)
+            } else {
+                (output_tmp.as_mut_ptr(), output_tmp.len() as Size)
+            };
+
             func(
                 plugin,
-                inputs.as_ptr(),
-                inputs.len() as Size,
-                output_tmp.as_mut_ptr(),
-                output_tmp.len() as Size,
+                inputs_ptr,
+                inputs_len,
+                output_ptr,
+                output_len,
                 user_data.as_ptr(),
             );
 
@@ -244,8 +266,8 @@ pub unsafe extern "C" fn extism_function_new(
                 match tmp.t {
                     ValType::I32 => *out = Val::I32(tmp.v.i32),
                     ValType::I64 => *out = Val::I64(tmp.v.i64),
-                    ValType::F32 => *out = Val::F32(tmp.v.f32 as u32),
-                    ValType::F64 => *out = Val::F64(tmp.v.f64 as u64),
+                    ValType::F32 => *out = Val::F32(tmp.v.f32.to_bits()),
+                    ValType::F64 => *out = Val::F64(tmp.v.f64.to_bits()),
                     _ => todo!(),
                 }
             }
@@ -280,6 +302,79 @@ pub unsafe extern "C" fn extism_function_set_namespace(
     }
 }
 
+/// Pre-compile an Extism plugin
+#[no_mangle]
+pub unsafe extern "C" fn extism_compiled_plugin_new(
+    wasm: *const u8,
+    wasm_size: Size,
+    functions: *mut *const ExtismFunction,
+    n_functions: Size,
+    with_wasi: bool,
+    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);
+
+    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) {
+    if plugin.is_null() {
+        return;
+    }
+
+    let plugin = Box::from_raw(plugin);
+    trace!("called extism_compiled_plugin_free");
+    drop(plugin)
+}
+
 /// Create a new plugin with host functions, the functions passed to this function no longer need to be manually freed using
 ///
 /// `wasm`: is a WASM module (wat or wasm) or a JSON encoded manifest
@@ -296,36 +391,70 @@ pub unsafe extern "C" fn extism_plugin_new(
     with_wasi: bool,
     errmsg: *mut *mut std::ffi::c_char,
 ) -> *mut Plugin {
-    trace!("Call to extism_plugin_new with wasm pointer {:?}", wasm);
     let data = std::slice::from_raw_parts(wasm, wasm_size as usize);
-    let mut funcs = vec![];
-
-    if !functions.is_null() {
-        for i in 0..n_functions {
-            unsafe {
-                let f = *functions.add(i as usize);
-                if f.is_null() {
-                    continue;
+    let funcs = if functions.is_null() {
+        vec![]
+    } else {
+        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");
                 }
-                if let Some(f) = (*f).0.take() {
-                    funcs.push(f);
-                } else {
-                    let e = std::ffi::CString::new(
-                        "Function cannot be registered with multiple different Plugins",
-                    )
-                    .unwrap();
+
+                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()
+            });
 
-    let plugin = Plugin::new(data, funcs, with_wasi);
+        if funcs.len() != n_functions as usize {
+            return std::ptr::null_mut();
+        }
+
+        funcs
+    };
+
+    Plugin::new(data, funcs, with_wasi)
+        .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()
+        })
+}
+
+/// Create a new plugin from an `ExtismCompiledPlugin`
+#[no_mangle]
+pub unsafe extern "C" fn extism_plugin_new_from_compiled(
+    compiled: *const CompiledPlugin,
+    errmsg: *mut *mut std::ffi::c_char,
+) -> *mut Plugin {
+    let plugin = Plugin::new_from_compiled(&*compiled);
     match plugin {
         Err(e) => {
             if !errmsg.is_null() {
-                let e = std::ffi::CString::new(format!("Unable to create Extism plugin: {}", e))
-                    .unwrap();
+                let e = std::ffi::CString::new(format!(
+                    "Unable to create Extism plugin: {}",
+                    e.root_cause(),
+                ))
+                .unwrap();
                 *errmsg = e.into_raw();
             }
             std::ptr::null_mut()
@@ -334,6 +463,100 @@ pub unsafe extern "C" fn extism_plugin_new(
     }
 }
 
+/// Create a new plugin and set the number of instructions a plugin is allowed to execute
+#[no_mangle]
+pub unsafe extern "C" fn extism_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 Plugin {
+    trace!(
+        "Call to extism_plugin_new_with_fuel_limit with wasm pointer {:?}",
+        wasm
+    );
+    let data = std::slice::from_raw_parts(wasm, wasm_size as usize);
+    let funcs = if functions.is_null() {
+        vec![]
+    } else {
+        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();
+        }
+
+        funcs
+    };
+
+    let compiled = match CompiledPlugin::new(
+        PluginBuilder::new(data)
+            .with_functions(funcs)
+            .with_wasi(with_wasi)
+            .with_fuel_limit(fuel_limit),
+    ) {
+        Ok(x) => x,
+        Err(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();
+            }
+            return std::ptr::null_mut();
+        }
+    };
+
+    let plugin = Plugin::new_from_compiled(&compiled);
+
+    match plugin {
+        Err(e) => {
+            if !errmsg.is_null() {
+                let e = std::ffi::CString::new(format!(
+                    "Unable to create Extism plugin: {}",
+                    e.root_cause(),
+                ))
+                .unwrap();
+                *errmsg = e.into_raw();
+            }
+            std::ptr::null_mut()
+        }
+        Ok(p) => Box::into_raw(Box::new(p)),
+    }
+}
+
+/// Enable HTTP response headers in plugins using `extism:host/env::http_request`
+#[no_mangle]
+pub unsafe extern "C" fn extism_plugin_allow_http_response_headers(plugin: *mut Plugin) {
+    let plugin = &mut *plugin;
+    plugin.store.data_mut().http_headers = Some(BTreeMap::new());
+}
+
 /// Free the error returned by `extism_plugin_new`, errors returned from `extism_plugin_error` don't need to be freed
 #[no_mangle]
 pub unsafe extern "C" fn extism_plugin_new_error_free(err: *mut std::ffi::c_char) {
@@ -343,7 +566,7 @@ pub unsafe extern "C" fn extism_plugin_new_error_free(err: *mut std::ffi::c_char
     drop(std::ffi::CString::from_raw(err))
 }
 
-/// Remove a plugin from the registry and free associated memory
+/// Free `ExtismPlugin`
 #[no_mangle]
 pub unsafe extern "C" fn extism_plugin_free(plugin: *mut Plugin) {
     if plugin.is_null() {
@@ -394,8 +617,6 @@ pub unsafe extern "C" fn extism_plugin_config(
         return false;
     }
     let plugin = &mut *plugin;
-    let _lock = plugin.instance.clone();
-    let mut lock = _lock.lock().unwrap();
 
     trace!(
         plugin = plugin.id.to_string(),
@@ -406,8 +627,8 @@ pub unsafe extern "C" fn extism_plugin_config(
     let json: std::collections::BTreeMap<String, Option<String>> =
         match serde_json::from_slice(data) {
             Ok(x) => x,
-            Err(e) => {
-                return plugin.return_error(&mut lock, e, false);
+            Err(_) => {
+                return false;
             }
         };
 
@@ -440,9 +661,6 @@ pub unsafe extern "C" fn extism_plugin_function_exists(
         return false;
     }
     let plugin = &mut *plugin;
-    let _lock = plugin.instance.clone();
-    let mut lock = _lock.lock().unwrap();
-
     let name = std::ffi::CStr::from_ptr(func_name);
     trace!(
         plugin = plugin.id.to_string(),
@@ -452,8 +670,8 @@ pub unsafe extern "C" fn extism_plugin_function_exists(
 
     let name = match name.to_str() {
         Ok(x) => x,
-        Err(e) => {
-            return plugin.return_error(&mut lock, e, false);
+        Err(_) => {
+            return false;
         }
     };
 
@@ -505,13 +723,14 @@ pub unsafe extern "C" fn extism_plugin_call_with_host_context(
     let lock = plugin.instance.clone();
     let mut lock = lock.lock().unwrap();
 
-    plugin.error_msg = None;
-
     // Get function name
     let name = std::ffi::CStr::from_ptr(func_name);
     let name = match name.to_str() {
         Ok(name) => name,
-        Err(e) => return plugin.return_error(&mut lock, e, -1),
+        Err(e) => {
+            plugin.error_msg = Some(make_error_msg(e.to_string()));
+            return -1;
+        }
     };
 
     trace!(
@@ -520,13 +739,17 @@ pub unsafe extern "C" fn extism_plugin_call_with_host_context(
         name
     );
     let input = std::slice::from_raw_parts(data, data_len as usize);
-    let r = match ExternRef::new(&mut plugin.store, CVoidContainer(host_context)) {
-        Err(e) => return plugin.return_error(&mut lock, e, -1),
-        Ok(x) => x,
+    let r = if host_context.is_null() {
+        None
+    } else {
+        Some(CVoidContainer(host_context))
     };
-    let res = plugin.raw_call(&mut lock, name, input, Some(r));
+    let res = plugin.raw_call(&mut lock, name, input, r);
     match res {
-        Err((e, rc)) => plugin.return_error(&mut lock, e, rc),
+        Err((e, rc)) => {
+            plugin.error_msg = Some(make_error_msg(e.to_string()));
+            rc
+        }
         Ok(x) => x,
     }
 }
@@ -549,6 +772,9 @@ pub unsafe extern "C" fn extism_plugin_error(plugin: *mut Plugin) -> *const c_ch
     let _lock = _lock.lock().unwrap();
 
     if plugin.output.error_offset == 0 {
+        if let Some(err) = &plugin.error_msg {
+            return err.as_ptr() as *const _;
+        }
         trace!(plugin = plugin.id.to_string(), "error is NULL");
         return std::ptr::null();
     }
@@ -640,7 +866,6 @@ pub unsafe extern "C" fn extism_log_file(
 fn set_log_file(log_file: impl Into<std::path::PathBuf>, filter: &str) -> Result<(), Error> {
     let log_file = log_file.into();
     let s = log_file.to_str();
-
     let is_level = tracing::Level::from_str(filter).is_ok();
     let cfg = tracing_subscriber::FmtSubscriber::builder().with_env_filter({
         let x = tracing_subscriber::EnvFilter::builder()
@@ -674,7 +899,7 @@ fn set_log_file(log_file: impl Into<std::path::PathBuf>, filter: &str) -> Result
     Ok(())
 }
 
-static mut LOG_BUFFER: Option<LogBuffer> = None;
+static LOG_BUFFER: std::sync::Mutex<Option<LogBuffer>> = std::sync::Mutex::new(None);
 
 /// Enable a custom log handler, this will buffer logs until `extism_log_drain` is called
 /// Log level should be one of: info, error, trace, debug, warn
@@ -691,6 +916,7 @@ pub unsafe extern "C" fn extism_log_custom(log_level: *const c_char) -> bool {
     } else {
         "error"
     };
+
     set_log_buffer(level).is_ok()
 }
 
@@ -705,8 +931,8 @@ unsafe fn set_log_buffer(filter: &str) -> Result<(), Error> {
             x.parse_lossy(filter)
         }
     });
-    LOG_BUFFER = Some(LogBuffer::default());
-    let buf = LOG_BUFFER.clone().unwrap();
+    *LOG_BUFFER.lock().unwrap() = Some(LogBuffer::default());
+    let buf = LOG_BUFFER.lock().unwrap().clone().unwrap();
     cfg.with_ansi(false)
         .with_writer(move || buf.clone())
         .try_init()
@@ -718,7 +944,7 @@ unsafe fn set_log_buffer(filter: &str) -> Result<(), Error> {
 /// Calls the provided callback function for each buffered log line.
 /// This is only needed when `extism_log_custom` is used.
 pub unsafe extern "C" fn extism_log_drain(handler: ExtismLogDrainFunctionType) {
-    if let Some(buf) = LOG_BUFFER.as_mut() {
+    if let Some(buf) = LOG_BUFFER.lock().unwrap().as_mut() {
         if let Ok(mut buf) = buf.buffer.lock() {
             for (line, len) in buf.drain(..) {
                 handler(line.as_ptr(), len as u64);

runtime/src/tests/issues.rs

@@ -1,6 +1,7 @@
 use crate::*;
 
 const WASM_EMPTY: &[u8] = include_bytes!("../../../wasm/empty.wasm");
+const WASM_UNREACHABLE: &[u8] = include_bytes!("../../../wasm/unreachable.wasm");
 
 // https://github.com/extism/extism/issues/620
 #[test]
@@ -26,3 +27,31 @@ host_fn!(
         Ok(path.display().to_string())
     }
 );
+
+// https://github.com/extism/extism/issues/775
+#[test]
+fn test_issue_775() {
+    // Load and build plugin
+    let url = Wasm::data(WASM_UNREACHABLE);
+    let manifest = Manifest::new([url]);
+    let mut plugin = PluginBuilder::new(manifest)
+        .with_wasi(true)
+        .build()
+        .unwrap();
+    // Call test method
+    let lock = plugin.instance.clone();
+    let mut lock = lock.lock().unwrap();
+    let res = plugin.raw_call(&mut lock, "do_unreachable", b"", None::<()>);
+    let p = match res {
+        Err(e) => {
+            if e.1 == 0 {
+                Err(e.1)
+            } else {
+                Ok(e.1)
+            }
+        }
+        Ok(code) => Err(code),
+    }
+    .unwrap();
+    println!("{}", p);
+}

runtime/src/tests/kernel.rs

@@ -3,36 +3,32 @@ use quickcheck::*;
 
 const KERNEL: &[u8] = include_bytes!("../extism-runtime.wasm");
 
-fn extism_alloc<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, n: u64) -> u64 {
+fn extism_alloc<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, n: u64) -> u64 {
     let out_alloc = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "alloc")
+        .get_func(&mut *store, "alloc")
         .unwrap()
-        .call(&mut store, &[Val::I64(n as i64)], out_alloc)
+        .call(store, &[Val::I64(n as i64)], out_alloc)
         .unwrap();
     out_alloc[0].unwrap_i64() as u64
 }
 
-fn extism_length<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
+fn extism_length<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
     let out = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "length")
+        .get_func(&mut *store, "length")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
 
-fn extism_length_unsafe<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-) -> u64 {
+fn extism_length_unsafe<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
     let out = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "length_unsafe")
+        .get_func(&mut *store, "length_unsafe")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
@@ -47,122 +43,96 @@ fn extism_load_u8<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance
     out[0].unwrap_i32() as u8
 }
 
-fn extism_load_u64<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
+fn extism_load_u64<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
     let out = &mut [Val::I32(0)];
     instance
-        .get_func(&mut store, "load_u64")
+        .get_func(&mut *store, "load_u64")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
 
-fn extism_input_load_u8<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-) -> u8 {
+fn extism_input_load_u8<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u8 {
     let out = &mut [Val::I32(0)];
     instance
-        .get_func(&mut store, "input_load_u8")
+        .get_func(&mut *store, "input_load_u8")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i32() as u8
 }
 
 fn extism_input_load_u64<T>(
-    mut store: &mut wasmtime::Store<T>,
+    store: &mut wasmtime::Store<T>,
     instance: &mut Instance,
     p: u64,
 ) -> u64 {
     let out = &mut [Val::I32(0)];
     instance
-        .get_func(&mut store, "input_load_u64")
+        .get_func(&mut *store, "input_load_u64")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
 
-fn extism_store_u8<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, x: u8) {
+fn extism_store_u8<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, x: u8) {
     instance
-        .get_func(&mut store, "store_u8")
+        .get_func(&mut *store, "store_u8")
         .unwrap()
-        .call(
-            &mut store,
-            &[Val::I64(p as i64), Val::I32(x as i32)],
-            &mut [],
-        )
+        .call(store, &[Val::I64(p as i64), Val::I32(x as i32)], &mut [])
         .unwrap();
 }
 
-fn extism_store_u64<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-    x: u64,
-) {
+fn extism_store_u64<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, x: u64) {
     instance
-        .get_func(&mut store, "store_u64")
+        .get_func(&mut *store, "store_u64")
         .unwrap()
-        .call(
-            &mut store,
-            &[Val::I64(p as i64), Val::I64(x as i64)],
-            &mut [],
-        )
+        .call(store, &[Val::I64(p as i64), Val::I64(x as i64)], &mut [])
         .unwrap();
 }
 
-fn extism_free<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
+fn extism_free<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
     instance
-        .get_func(&mut store, "free")
+        .get_func(&mut *store, "free")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], &mut [])
+        .call(store, &[Val::I64(p as i64)], &mut [])
         .unwrap();
 }
 
-fn extism_error_set<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
+fn extism_error_set<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
     instance
-        .get_func(&mut store, "error_set")
+        .get_func(&mut *store, "error_set")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], &mut [])
+        .call(store, &[Val::I64(p as i64)], &mut [])
         .unwrap();
 }
 
-fn extism_error_get<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance) -> u64 {
+fn extism_error_get<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance) -> u64 {
     let out = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "error_get")
+        .get_func(&mut *store, "error_get")
         .unwrap()
-        .call(&mut store, &[], out)
+        .call(store, &[], out)
         .unwrap();
 
     out[0].unwrap_i64() as u64
 }
 
-fn extism_reset<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance) {
+fn extism_reset<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance) {
     instance
-        .get_func(&mut store, "reset")
+        .get_func(&mut *store, "reset")
         .unwrap()
-        .call(&mut store, &[], &mut [])
+        .call(store, &[], &mut [])
         .unwrap();
 }
 
-fn extism_input_set<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-    l: u64,
-) {
+fn extism_input_set<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, l: u64) {
     instance
-        .get_func(&mut store, "input_set")
+        .get_func(&mut *store, "input_set")
         .unwrap()
-        .call(
-            &mut store,
-            &[Val::I64(p as i64), Val::I64(l as i64)],
-            &mut [],
-        )
+        .call(store, &[Val::I64(p as i64), Val::I64(l as i64)], &mut [])
         .unwrap();
 }
 
@@ -183,9 +153,29 @@ fn test_kernel_allocations() {
     // Test allocations
     assert_eq!(extism_alloc(&mut store, instance, 0), 0);
 
+    // 512 bytes, test block re-use + splitting
+    let p = extism_alloc(&mut store, instance, 65535);
+    let first_alloc = p;
+    assert_eq!(extism_length(&mut store, instance, p), 65535);
+    assert_eq!(extism_length(&mut store, instance, p + 1), 0);
+    assert_eq!(extism_length(&mut store, instance, p + 2), 0);
+    assert_eq!(extism_length(&mut store, instance, p + 3), 0);
+    assert_eq!(extism_length(&mut store, instance, p + 4), 0);
+    extism_free(&mut store, instance, p);
+
+    // Should re-use the previous block
+    let q = extism_alloc(&mut store, instance, 65535);
+    assert_eq!(q, p);
+    assert_eq!(extism_length(&mut store, instance, q), 65535);
+    extism_free(&mut store, instance, q);
+
+    let r = extism_alloc(&mut store, instance, 65535 - 24);
+    assert_eq!(r, q);
+    assert_eq!(extism_length(&mut store, instance, q), 65535 - 24);
+    extism_free(&mut store, instance, r);
+
     // 1 byte
     let p = extism_alloc(&mut store, instance, 1);
-    let first_alloc = p;
     assert!(p > 0);
     assert_eq!(extism_length(&mut store, instance, p), 1);
     assert_eq!(extism_length_unsafe(&mut store, instance, p), 1);
@@ -205,37 +195,8 @@ fn test_kernel_allocations() {
         assert_eq!(extism_length(&mut store, instance, p), 64 - i);
         assert_eq!(extism_length_unsafe(&mut store, instance, p), 64 - i);
         extism_free(&mut store, instance, p);
-
-        // should re-use the last allocation
-        let q = extism_alloc(&mut store, instance, 64 - i);
-        assert_eq!(p, q);
-        assert_eq!(extism_length(&mut store, instance, q), 64 - i);
-        assert_eq!(extism_length_unsafe(&mut store, instance, q), 64 - i);
-        extism_free(&mut store, instance, q);
     }
 
-    // 512 bytes, test block re-use + splitting
-    let p = extism_alloc(&mut store, instance, 512);
-    assert_eq!(extism_length(&mut store, instance, p), 512);
-    assert_eq!(extism_length(&mut store, instance, p + 1), 0);
-    assert_eq!(extism_length(&mut store, instance, p + 2), 0);
-    assert_eq!(extism_length(&mut store, instance, p + 3), 0);
-    assert_eq!(extism_length(&mut store, instance, p + 4), 0);
-    extism_free(&mut store, instance, p);
-
-    // 128 bytes, should be split off the 512 byte block
-    let q = extism_alloc(&mut store, instance, 128);
-    assert!(p <= q && q < p + 512);
-    assert_eq!(extism_length(&mut store, instance, q), 128);
-    extism_free(&mut store, instance, q);
-
-    // 128 bytes, same as above
-    let r = extism_alloc(&mut store, instance, 128);
-    assert!(p <= r && r < p + 512);
-    assert!(r > p);
-    assert_eq!(extism_length(&mut store, instance, r), 128);
-    extism_free(&mut store, instance, q);
-
     // 100 pages
     let p = extism_alloc(&mut store, instance, 6553600);
     assert!(p > 0);

runtime/src/tests/runtime.rs

@@ -1,7 +1,7 @@
-use extism_manifest::MemoryOptions;
+use extism_manifest::{HttpRequest, MemoryOptions};
 
 use crate::*;
-use std::{io::Write, time::Instant};
+use std::{collections::HashMap, io::Write, time::Instant};
 
 const WASM: &[u8] = include_bytes!("../../../wasm/code-functions.wasm");
 const WASM_NO_FUNCTIONS: &[u8] = include_bytes!("../../../wasm/code.wasm");
@@ -9,6 +9,7 @@ const WASM_LOOP: &[u8] = include_bytes!("../../../wasm/loop.wasm");
 const WASM_GLOBALS: &[u8] = include_bytes!("../../../wasm/globals.wasm");
 const WASM_REFLECT: &[u8] = include_bytes!("../../../wasm/reflect.wasm");
 const WASM_HTTP: &[u8] = include_bytes!("../../../wasm/http.wasm");
+const WASM_HTTP_HEADERS: &[u8] = include_bytes!("../../../wasm/http_headers.wasm");
 const WASM_FS: &[u8] = include_bytes!("../../../wasm/read_write.wasm");
 
 host_fn!(pub hello_world (a: String) -> String { Ok(a) });
@@ -242,6 +243,40 @@ fn test_timeout() {
 }
 
 #[test]
+fn test_fuel() {
+    let manifest = Manifest::new([extism_manifest::Wasm::data(WASM_LOOP)]);
+    let mut plugin = PluginBuilder::new(manifest)
+        .with_wasi(true)
+        .with_fuel_limit(1)
+        .build()
+        .unwrap();
+    for _ in 0..10001 {
+        let output: Result<&[u8], Error> = plugin.call("loop_forever", "abc123");
+        let err = output.unwrap_err().root_cause().to_string();
+        println!("Fuel limited plugin exited with error: {:?}", &err);
+        assert!(err.contains("fuel"));
+    }
+}
+
+#[test]
+fn test_fuel_consumption() {
+    let manifest = Manifest::new([extism_manifest::Wasm::data(WASM_LOOP)]);
+    let mut plugin = PluginBuilder::new(manifest)
+        .with_wasi(true)
+        .with_fuel_limit(10000)
+        .build()
+        .unwrap();
+
+    let output: Result<&[u8], Error> = plugin.call("loop_forever", "abc123");
+    assert!(output.is_err());
+
+    let fuel_consumed = plugin.fuel_consumed().unwrap();
+    println!("Fuel consumed: {}", fuel_consumed);
+    assert!(fuel_consumed > 0);
+}
+
+#[test]
+#[cfg(feature = "http")]
 fn test_http_timeout() {
     let f = Function::new(
         "hello_world",
@@ -317,8 +352,10 @@ fn test_multiple_instantiations() {
 #[test]
 fn test_globals() {
     let mut plugin = Plugin::new(WASM_GLOBALS, [], true).unwrap();
-    for i in 0..100000 {
-        let Json(count) = plugin.call::<_, Json<Count>>("globals", "").unwrap();
+    for i in 0..100001 {
+        let Json(count) = plugin
+            .call_with_host_context::<_, Json<Count>, _>("globals", "", ())
+            .unwrap();
         assert_eq!(count.count, i);
     }
 }
@@ -349,7 +386,7 @@ fn test_call_with_host_context() {
         [PTR],
         UserData::default(),
         |current_plugin, _val, ret, _user_data: UserData<()>| {
-            let foo = current_plugin.host_context::<Foo>()?;
+            let foo = current_plugin.host_context::<Foo>()?.clone();
             let hnd = current_plugin.memory_new(foo.message)?;
             ret[0] = current_plugin.memory_to_val(hnd);
             Ok(())
@@ -427,7 +464,7 @@ fn hello_world_set_error(
     _user_data: UserData<()>,
 ) -> Result<(), Error> {
     plugin.set_error("TEST")?;
-    outputs[0] = inputs[0].clone();
+    outputs[0] = inputs[0];
     Ok(())
 }
 
@@ -524,7 +561,7 @@ fn hello_world_user_data(
     let mut data = data.lock().unwrap();
     let s = _plugin.memory_get_val(&inputs[0])?;
     data.write_all(s)?;
-    outputs[0] = inputs[0].clone();
+    outputs[0] = inputs[0];
     Ok(())
 }
 
@@ -768,9 +805,39 @@ fn test_readonly_dirs() {
     assert_eq!(res, "hello world!");
 
     let line = "hello world 2";
-    let res2 = plugin.call::<&str, &str>("try_write", &line);
+    let res2 = plugin.call::<&str, &str>("try_write", line);
     assert!(
         res2.is_err(),
         "Expected try_write to fail, but it succeeded."
     );
 }
+
+#[test]
+#[cfg(feature = "http")]
+fn test_http_response_headers() {
+    let mut plugin = PluginBuilder::new(
+        Manifest::new([Wasm::data(WASM_HTTP_HEADERS)]).with_allowed_host("extism.org"),
+    )
+    .with_http_response_headers(true)
+    .build()
+    .unwrap();
+    let req = HttpRequest::new("https://extism.org");
+    let Json(res): Json<HashMap<String, String>> = plugin.call("http_get", Json(req)).unwrap();
+    println!("{:?}", res);
+    assert_eq!(res["content-type"], "text/html; charset=utf-8");
+}
+
+#[test]
+#[cfg(feature = "http")]
+fn test_http_response_headers_disabled() {
+    let mut plugin = PluginBuilder::new(
+        Manifest::new([Wasm::data(WASM_HTTP_HEADERS)]).with_allowed_host("extism.org"),
+    )
+    .with_http_response_headers(false)
+    .build()
+    .unwrap();
+    let req = HttpRequest::new("https://extism.org");
+    let Json(res): Json<HashMap<String, String>> = plugin.call("http_get", Json(req)).unwrap();
+    println!("{:?}", res);
+    assert!(res.is_empty());
+}

runtime/src/timer.rs

@@ -22,18 +22,18 @@ pub(crate) struct Timer {
 
 #[cfg(not(target_family = "windows"))]
 extern "C" fn cleanup_timer() {
-    let mut timer = match unsafe { TIMER.lock() } {
+    let mut timer = match TIMER.lock() {
         Ok(x) => x,
         Err(e) => e.into_inner(),
     };
     drop(timer.take());
 }
 
-static mut TIMER: std::sync::Mutex<Option<Timer>> = std::sync::Mutex::new(None);
+static TIMER: std::sync::Mutex<Option<Timer>> = std::sync::Mutex::new(None);
 
 impl Timer {
     pub(crate) fn tx() -> std::sync::mpsc::Sender<TimerAction> {
-        let mut timer = match unsafe { TIMER.lock() } {
+        let mut timer = match TIMER.lock() {
             Ok(x) => x,
             Err(e) => e.into_inner(),
         };
@@ -92,25 +92,39 @@ impl Timer {
             loop {
                 if plugins.is_empty() {
                     if let Ok(x) = rx.recv() {
-                        handle!(x)
+                        handle!(x);
                     }
                 }
 
-                plugins = plugins
-                    .into_iter()
-                    .filter(|(_k, (engine, end))| {
-                        if let Some(end) = end {
-                            let now = std::time::Instant::now();
-                            if end <= &now {
-                                engine.increment_epoch();
-                                return false;
+                let mut timeout: Option<std::time::Duration> = None;
+
+                plugins.retain(|_k, (engine, end)| {
+                    if let Some(end) = end {
+                        let now = std::time::Instant::now();
+                        if *end <= now {
+                            engine.increment_epoch();
+                            return false;
+                        } else {
+                            let time_left =
+                                (*end - now).saturating_sub(std::time::Duration::from_millis(1));
+                            if let Some(t) = &timeout {
+                                if time_left < *t {
+                                    timeout = Some(time_left);
+                                }
+                            } else {
+                                timeout = Some(time_left);
                             }
                         }
-                        true
-                    })
-                    .collect();
+                    }
 
-                for x in rx.try_iter() {
+                    true
+                });
+
+                if let Some(timeout) = timeout {
+                    if let Ok(x) = rx.recv_timeout(timeout) {
+                        handle!(x)
+                    }
+                } else if let Ok(x) = rx.recv() {
                     handle!(x)
                 }
             }