Blanc: BLockchAiN Contract toolchain

3 min readJan 12, 2021

turnpike/blanc

Welcome to Blanc! Blanc is the toolchain for WebAssembly-based blockchain contracts, and the name of "BLANC" comes from…

github.com

Some of you who read my articles might know I have released the customized version of eosio.cdt, which is the comprehensive SDK for building the WebAssembly (WASM) smart contracts working on EOSIO platforms and officially provided by block.one. I called it eoscc, but now it's Blanc.

Blanc is the toolchain for WebAssembly-based blockchain contracts, and the name of "BLANC" comes from BLockchAiN Contract toolchain. Currently, Blanc supports EOSIO only, but I have a plan to support other WebAssembly-based contracts like Cosmwasm which is widely used in blockchains based on Cosmos SDK (It is well known for its consensus algorithm, Tendermint). Someday, if eWASM is adopted in Ethereum 2.0, it can belong to the scope of supported profile of Blanc.

Blanc is adapted from eosio.cdt, but has a different approach from it. The major difference between them is that eosio.cdt uses the modified version of Clang/LLVM to maximize its features, but Blanc uses the vanilla (unmodified) Clang/LLVM for easier maintenance and faster adoption of state-of-the-art technologies. Because of heavy modifications on Clang/LLVM of eosio.cdt, users should wait for block.one's updates to utilize the latest Clang/LLVM. At this point in time (January, 2021), eosio.cdt uses Clang-7 and its upcoming release uses Clang-9, but Blanc uses Clang-11. Clang-12 is under development, but you can still use it with Blanc. The only thing you need to care about is that your Clang/LLVM installed in your system supports Clang plugins and WASM binary generation. You should have Clang-11 or higher, and for MacOS, you need to install llvm Package by brew. Clang/LLVM installed by Xcode were not built for supporting plugins.

By using the latest Clang/LLVM, generated WASM binaries will have smaller size by about 10%. (eg. eosio.token 18KB → 16KB, eosio.system 276KB → 252KB) All unit tests provided by eosio.cdt and eosio.contracts are passed and all generated ABIs are identical. I lowered the version of Blanc to 0.8.0, because there remain many parts to be cleaned up, but it supports the same features of eosio.cdt v1.7.0.

When Blanc compiles C++ source code, it generates intermediate source file and its description temporarily for supporting EOSIO-specific C++11 attributes like [[eosio::action]] and generating ABI or action dispatcher. For this code generation, Blanc utilizes Clang (11 or higher) tool and plugins, and generated files will be compiled by Clang again. Blanc searches for clang++-11 from system installation path like /usr/bin in Linux, but also clang++ is set to fallback, so you can run Blanc with another version of Clang without installing Clang-11.

How to Install Blanc

Ubuntu 20.04

Install Clang/LLVM 11 from llvm.org:

bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)"

Install Blanc:

bash -c "$(wget -O - https://raw.githubusercontent.com/turnpike/blanc/develop/blanc.sh)"

MacOS Big Sur

Install Clang/LLVM 11 by brew:

brew install llvm