This release fixes a bug in the optimizer (more about this on the blog), introduces the standard JSON interface, adds interface contracts and implements some additional safety checks.

The standard JSON interface provides a unified way to invoke the Solidity compiler in order to ease cross-platform adoption and compilation verification.


  • Implement the Standard JSON Input / Output API
  • Support interface contracts.
  • C API (jsonCompiler): Add the compileStandard() method to process a Standard JSON I/O.
  • Commandline interface: Add the standard-json parameter to process a Standard JSON I/O.
  • Commandline interface: Support allow-paths to define trusted import paths. Note: the path(s) of the supplied source file(s) is always trusted.
  • Inline Assembly: Storage variable access using _slot and _offset suffixes.
  • Inline Assembly: Disallow blocks with unbalanced stack.
  • Static analyzer: Warn about statements without effects.
  • Static analyzer: Warn about unused local variables, parameters, and return parameters.
  • Syntax checker: issue deprecation warning for unary ‘+’


  • Assembly output: Implement missing AssemblyItem types.
  • Compiler interface: Fix a bug where source indexes could be inconsistent between Solidity compiled with different compilers (clang vs. gcc) or compiler settings. The bug was visible in AST and source mappings.
  • Gas Estimator: Reflect the most recent fee schedule.
  • Type system: Contract inheriting from base with unimplemented constructor should be abstract.
  • Optimizer: Number representation bug in the constant optimizer fixed.

A big thank you to all contributors who helped make this release possible!

Download the new version of Solidity here.