add wasmtime-wasi-io and custom async executor to min-platform example (bytecodealliance#10128)

* add wasmtime-wasi-io and custom async executor to min-platform example

* make it possible to find example from wasmtime-wasi-io docs

prtest:full

* fix comment

* add wasm32-wasip2 target for min-platform ci

and enable signals based traps when running with wasi disabled,
because at the moment without signals based traps no native code can be
loaded so the embedding never actually executes wasm. this ensures the
heap size setting when not(feature = "wasi") is checked by execution

* fix cbindgen version in ci

Author: pchickey

.github/workflows/main.yml

@@ -951,8 +951,9 @@ jobs:
       with:
         submodules: true
     - uses: ./.github/actions/install-rust
-    - run: cargo install cbindgen --vers "^0.27" --locked
+    - run: cargo install cbindgen --vers "^0.28" --locked
     - run: rustup target add x86_64-unknown-none
+    - run: rustup target add wasm32-wasip2
     - run: ./build.sh x86_64-unknown-none
       working-directory: ./examples/min-platform
 
@@ -966,6 +967,12 @@ jobs:
       env:
         WASMTIME_SIGNALS_BASED_TRAPS: 1
 
+    - run: ./build.sh x86_64-unknown-none
+      working-directory: ./examples/min-platform
+      env:
+        WASMTIME_SIGNALS_BASED_TRAPS: 1
+        MIN_PLATFORM_TEST_DISABLE_WASI: 1
+
     # Add the `wasmtime-platform.h` file as a release artifact
     - uses: actions/upload-artifact@v4
       with:

Cargo.lock

@@ -13,7 +13,9 @@
 //! and write to streams.
 //!
 //! This crate is designed to have no unnecessary dependencies and, in
-//! particular, to be #![no_std].
+//! particular, to be #![no_std]. For an example no_std embedding, see
+//! [`/examples/min-platform`](https://github.com/bytecodealliance/wasmtime/tree/main/examples/min-platform)
+//! at the root of the wasmtime repo.
 
 #![no_std]
 
@@ -30,6 +32,9 @@ pub mod streams;
 #[doc(no_inline)]
 pub use async_trait::async_trait;
 
+#[doc(no_inline)]
+pub use ::bytes;
+
 use alloc::boxed::Box;
 use wasmtime::component::ResourceTable;
 

crates/wasi-io/src/lib.rs

@@ -15,4 +15,6 @@ object = { workspace = true, features = ['std'] }
 wasmtime = { workspace = true, features = ['cranelift', 'wat'] }
 
 [features]
+default = ["wasi"]
 custom = []
+wasi = [ "wasmtime/component-model" ]

examples/min-platform/Cargo.toml

@@ -26,6 +26,15 @@ if [ "$WASMTIME_SIGNALS_BASED_TRAPS" = "1" ]; then
   features="$features,custom"
 fi
 
+if [ "$MIN_PLATFORM_EXAMPLE_DISABLE_WASI" != "1" ]; then
+  features="$features,wasi"
+  cargo build \
+      --manifest-path=$REPO_DIR/examples/wasm/Cargo.toml \
+      --target wasm32-wasip2 \
+      --release
+  WASI_EXAMPLE_PATH=$REPO_DIR/target/wasm32-wasip2/release/wasi.wasm
+fi
+
 # First compile the C implementation of the platform symbols that will be
 # required by our embedding. This is the `embedding/wasmtime-platform.c` file.
 # The header file used is generated from Rust source code with the `cbindgen`
@@ -49,6 +58,7 @@ clang -shared -O2 -o "$HOST_DIR/libwasmtime-platform.so" "$EMBEDDING_DIR/wasmtim
 cargo build \
   --manifest-path $EMBEDDING_DIR/Cargo.toml \
   --target $target \
+  --no-default-features \
   --features "$features" \
   --release
 cc \
@@ -61,7 +71,8 @@ cc \
 
 # The final step here is running the host, in the current directory, which will
 # load the embedding and execute it.
-cargo run --manifest-path "$HOST_DIR/Cargo.toml" --release --features "$features" -- \
+cargo run --manifest-path "$HOST_DIR/Cargo.toml" --release --no-default-features --features "$features" -- \
   "$target" \
   "$HOST_DIR/libembedding.so" \
-  "$HOST_DIR/libwasmtime-platform.so"
+  "$HOST_DIR/libwasmtime-platform.so" \
+  $WASI_EXAMPLE_PATH

examples/min-platform/build.sh

@@ -16,6 +16,9 @@ anyhow = { workspace = true }
 # format so `cranelift` and `wat` are enabled.
 wasmtime = { workspace = true, features = ['runtime'] }
 
+# Following deps are only required for wasi portion:
+wasmtime-wasi-io = { workspace = true, optional = true }
+
 # Memory allocator used in this example (not required, however)
 dlmalloc = "0.2.4"
 
@@ -25,4 +28,10 @@ test = false
 doctest = false
 
 [features]
+default = ["wasi"]
 custom = ['wasmtime/custom-virtual-memory', 'wasmtime/custom-native-signals']
+wasi = [
+    'wasmtime/component-model',
+    'wasmtime/async',
+    'dep:wasmtime-wasi-io',
+]

examples/min-platform/embedding/Cargo.toml

@@ -63,7 +63,12 @@ unsafe impl GlobalAlloc for MyGlobalDmalloc {
     }
 }
 
+#[cfg(not(feature = "wasi"))]
 const INITIAL_HEAP_SIZE: usize = 64 * 1024;
+// The wasi component requires a larger heap than the module tests
+#[cfg(feature = "wasi")]
+const INITIAL_HEAP_SIZE: usize = 4 * 1024 * 1024;
+
 static mut INITIAL_HEAP: [u8; INITIAL_HEAP_SIZE] = [0; INITIAL_HEAP_SIZE];
 static mut INITIAL_HEAP_ALLOCATED: bool = false;
 

examples/min-platform/embedding/src/allocator.rs

@@ -10,6 +10,9 @@ use wasmtime::{Engine, Instance, Linker, Module, Store};
 mod allocator;
 mod panic;
 
+#[cfg(feature = "wasi")]
+mod wasi;
+
 /// Entrypoint of this embedding.
 ///
 /// This takes a number of parameters which are the precompiled module AOT