Add Wasmtime v44.0.1 as a second WebAssembly execution engine, selectable at runtime via the new featureWasmtimeEngine Amendment. When the Amendment is enabled, hook execution and WASM validation switch from WasmEdge to Wasmtime.
sfHookInstructionCount changes semantics to fuel consumed (initial budget: 10,000,000,000 units); fee calculation is redefined accordingly.
New files:
- external/wasmtime/conanfile.py + conandata.yml — prebuilt C API binary package (macOS arm64, Linux x86_64; SHA256-pinned at v44.0.1)
- cmake/deps/Wasmtime.cmake — find_package(wasmtime REQUIRED)
- src/.../WasmtimeEngine.h/.cpp — IWasmEngine implementation
Build system changes:
- CMakeLists.txt, conanfile.py: with_wasmtime option (default on)
- cmake/RippledCore.cmake: link wasmtime::wasmtime alongside wasmedge::wasmedge
Protocol changes:
- features.macro: XRPL_FEATURE(WasmtimeEngine, Supported::yes, DefaultNo)
- WasmEngine.h: constexpr kWasmtimeInitialFuel = 10'000'000'000ULL (consensus-fixed)
- applyHook.cpp, SetHook.cpp, Change.cpp: engine selected by featureWasmtimeEngine
Implementation notes:
- Consensus-fixed config: consume_fuel=true, wasm_simd=true, relaxed_simd=false, reference_types=true, bulk_memory=true, multi_value=false, nan_canonicalization=true
- Termination ABI: accept/rollback sets ExecState::terminated flag then returns a wasm_trap_t* to unwind the guest; execute() checks the flag before inspecting callErr to distinguish clean termination from errors
- Memory access workaround (ensureMemoryExported): Wasmtime lacks an index-based memory accessor equivalent to WasmEdge_CallingFrameGetMemoryInstance. The binary is patched before instantiation to inject a "memory" export when the module owns memory without exporting it, enabling wasmtime_caller_export_get() inside host callbacks.
Introduce an engine-agnostic abstraction so that <wasmedge/wasmedge.h> is included only in WasmEdgeEngine.cpp, enabling future execution engines to be plugged in without touching Hook API implementation code.
New files:
- include/xrpl/hook/WasmTypes.h – GuestMemory, WasmValue, HostFunctionDecl
- src/.../hook/detail/WasmEngine.h – IWasmEngine pure virtual interface, ExecutionResult, hookHostFunctionDecls()
- src/.../hook/detail/WasmEdgeEngine.h/.cpp – WasmEdge implementation; the sole consumer of wasmedge.h
Key changes:
- Macro.h: replace WasmEdge_* types with engine-agnostic WasmValue/GuestMemory; DEFINE_HOOK_FUNCTION now returns HostCallStatus via a thin wrapper
- applyHook.h: remove wasmedge.h include and HookExecutor class entirely
- applyHook.cpp: call makeWasmEdgeEngine()->execute() at the single call site
- SetHook.cpp, Change.cpp: call makeWasmEdgeEngine()->validate() for WASM validation instead of HookExecutor::validateWasm()
No behavioral change; no Amendment required.
