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Reproducible contract builds

Reproducible contract builds across all supported platforms is a goal of the compiler. We implement the following precautionary measures aiding reproducible builds:

  • Avoid datastructures with (random) state when iteration is required.
  • Including all bytecode altering compiler options as custom extensions in the standard JSON input.
  • Providing statically linked resolc linux binaries.
  • Continuous testing for reproducible builds using a large corpus.
  • Exposing all bytecode altering compiler configuration in the standard JSON input.

Any case where not possible to reproduce the build accross any support platform are treated as a bug. If you believe to have uncovered a case violating reproducibility of contract builds please do not hesitate to open an issue providing an exact reproducer.

Requirements​

In order to reproduce and thus verify the byte code of an on-chain contract by matching its code hash, the following information is needed:

  • The Solidity sources including all dependencies.
  • The resolc version used during the build process.
  • The solc version used during the build process.
  • Any byte code altering compiler options (see below) or the standard JSON input that was supplied to resolc.

Byte code altering compiler options​

The following resolc CLI options influence the byte code of compiled contracts:

  • -g
  • -O
  • --heap-size
  • --stack-size
  • --llvm-arg
  • --disable-solc-optimizer
  • --fallback-Oz