BAC-L1-SUB-103Substrate / Polkadot SDK
Rust for the constrained runtime environment
A runtime compiles to WebAssembly: no standard library, no implicit allocation, no non-determinism. The rules change.
- Level
- L1 — Blockchain developer
- Duration
- 4 h
- Maintainer
- Polkadot / Substrate Lead Architect
Learning objectives
- 01Build a module in a no-standard-library environment
- 02Encode and decode structures with a compact codec
- 03Identify the sources of non-determinism forbidden in a runtime
Guided lab
Convert an existing module to the constrained environment and compile it to WebAssembly.
Independent lab
Measure the resulting WebAssembly binary size and reduce it through documented design choices.
Security angle
Floating point, system clock, randomness not supplied by the chain: three ways to break determinism and thus consensus.
Assessment
Module compiled to WebAssembly, with a note on the non-determinism sources eliminated.