Hera

Hera is an eWASM virtual machine implemented in C++ conforming to the Ethereum VM API.

It can be used with cpp-ethereum and perhaps in the future with other implementations through appropriate bindings.

Currently it uses Binaryen's interpreter for running WebAssembly bytecode and it should be improved to support the WAVM as a backend.

Build options

• -DHERA_DEBUGGING=ON will turn on debugging features and messages
• -DHERA_METERING_CONTRACT=ON will pass contract creation data through the metering contract residing at 0x00..0a

Interfaces

Hera implements two interfaces: EEI and a debugging module.

Debugging module

• debug::print32(value: i32) - print value
• debug::print64(value: i64) - print value
• debug::printMem(offset: i32, len: i32) - print memory segment as printable characters
• debug::printMemHex(offset: i32, len: i32) - print memory segment as hex
• debug::printStorage(pathOffset: i32) - print storage value as printable characters
• debug::printStorageHex(pathOffset: i32) - print storage value as hex

These are only enabled if Hera is compiled with debugging on.

Caveats

Although Hera enables the execution of eWASM bytecode, there are more elements to eWASM an Ethereum node must be aware of:

• backwards compatibility provisions
• injecting metering code to eWASM contracts
• transcompiling EVM1 contracts to eWASM if desired

All of the above must be implemented outside of Hera.

Author(s)

Alex Beregszaszi

License

MIT