WAVM for XuperChain

This is a XuperChain WASM Virtual Machine based on WAVM/WAVM, most of the changes compared to the original repo are that we add gas metering to the wasm code and provide a golang wrapper. All the changes are not invasive to the original WAVM.

C/C++ code compiled with emscripten can run on WAVM without any other resolvers. For other languages it doesn’t support yet.

Quick start

Requirements:

• GCC 5.x
• LLVM 8.0.0 (recommended)
• XuperUnion v3.1

Standalone

If you try to test the new fetures like gas metering, just do as the original repository tells you : Building WAVM

we also provide a more unix-like way to build:

1. install llvm and clang by here, assume your installation directory is ${llvm_install_dir}
2. build

cd ${source-to-wavm}
CXX=${llvm_install_dir}/bin/clang++ CC=${llvm_install_dir}/bin/clang LLVMDIR=${llvm_install_dir}/lib/cmake/llvm make

Then run this command, you will get the gas used as the debug output.

./output/wavm-run -d ../Example/hello.wast

XuperChain

XuperChain is pluggable cause almost all the component included is pluggable, so is smart contract virtual machine. There are three steps to make it work.

1. Compile WAVM.

   cd ${source-to-wavm}
   CXX=${llvm_install_dir}/bin/clang++ CC=${llvm_install_dir}/bin/clang LLVMDIR=${llvm_install_dir}/lib/cmake/llvm make

2. cd ${source-to-wavm}, run make to build the plugin, copy it to the plugins directory, then add or update plugins.conf with

   "wasm":[{
   "subtype":"wavm",
   "path": "plugins/vm/wavm.so",
   "version": "1.0.0",
   "ondemand": false
   }]

3. Add the configure to xchain.yaml:

   wasm:
   driver: wavm
   external: true

external means it should be loaded as a plugin. Be careful that shim depends on xuperunion(which should be compiled by enabling GO111MODULE=on without -mod=vendor, remove the export GOFLAGS=-mod=vendor from xuperchain’s Makefile), so make sure that shim requires the same version of xuperunion who load this plugin,

or an error as below maybe occur:

Warn: plugin open failed!" module=pluginmgr pluginname=wasm 
err="plugin.Open(\"plugins/wavm\"): plugin was built with a different version of package github.com/xuperchain/xuperunion/..."

FAQ

1. libWAVM.so: cannot open shared object file: No such file or directory”

libWAVM.so is in the ${source-to-wavm}/WAVM/output by default. so if you intend to deploy wavm.so to other server, you can copy the libWAVM.so to any directory and set environment LD_LIBRARY_PATH to this directory.