This project demonstrates the pattern:

• A program compiled to wasm32-unknown-unknown that uses V8 API symbols.
• The V8 API is provided as imported functions at runtime.
• The wasm binary does not embed the V8 engine.

• guest/tests/*.cpp: default test sources.
• guest/tests/manifest.json: default test registry used by host integration tests.
• guest/build-test-native.sh: builds native test binaries.
• guest/build-test-wasix.sh: builds WASIX test wasm modules.
• host/: Wasmer 7.0 runtime that resolves guest imports via real libv8.dylib.
• host/tests/wasix_examples_compare.rs: compares native and WASIX outputs.

1. Build one guest test (native + WASIX):

./guest/build-test-native.sh version_printf
./guest/build-test-wasix.sh version_printf

2. Run host (Rust 1.91+; this repo includes rust-toolchain.toml):

cargo run -p v8_host -- target/wasm32-wasix/release/version_printf.wasm wasix

Expected output:

V8_VERSION_STRING=14.5.201.9
wasix_exit_code=0

Guest tests use V8 public headers (v8-version.h, v8-version-string.h) and compile to both native and WASIX artifacts. The host runs WASIX modules with wasmer-wasix, and test assertions enforce native vs WASIX output parity.

Run:

cargo test -p v8_host

This validates one default path:

• native stdout equals WASIX stdout for each test case.

The default test list is loaded from guest/tests/manifest.json, so adding a new parity test is:

1. add guest/tests/<name>.cpp
2. add <name> to guest/tests/manifest.json
3. run cargo test -p v8_host

Current coverage set (easy -> medium):

• version_printf (v8-version-string.h)
• version_numbers_printf (v8-version.h)
• version_string_printf (v8-version-string.h)
• getversion_signature_printf (v8::V8::GetVersion signature contract)
• setflags_from_string_printf (v8::V8::SetFlagsFromString runtime imports)

• No custom guest APIs: guest tests only call V8 headers APIs.
• Host import names: C++ mangled symbols (for example _ZN2v82V810GetVersionEv) are bound in host/src/lib.rs.
• Pointer-return APIs: if an API returns host memory pointers, host trampolines copy stable bytes into guest memory and return a guest pointer.
• WASIX modules: use wasmer-wasix runner imports as the default runtime path.

Before moving to lifecycle APIs, keep these acceptance criteria:

• cargo test -p v8_host is fully green.
• every new API test has deterministic native vs WASIX stdout parity.
• no flaky behavior across repeated runs.

Planned medium-difficulty next API family:

• v8::V8::SetFlagsFromCommandLine(...) (argv pointer mapping and post-parse argc/argv validation).