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Solidity 0.5.5 Release Announcement

Posted by Solidity Team on March 5, 2019


This release focuses on the stabilization of the ABIEncoderV2 and the optimizer. We also prepared for the Petersburg release which is the default EVM now and improved the SMT checker, such that it now reports less false positives when using SafeMath. You can now activate the experimental Yul optimizer using settings: {optimizer: {enabled: true, details: {yul: true}}} or in the commandline via solc optimize-yul.

Language Features:

  • Add support for getters of mappings with string or bytes key types.
  • Meta programming: Provide access to the name of contracts via type(C).name.

Compiler Features:

  • Support petersburg as evmVersion and set as default.
  • Commandline Interface: Option to activate the experimental yul optimizer using -optimize-yul.
  • Inline Assembly: Consider extcodehash as part of Constantinople.
  • Inline Assembly: Instructions unavailable to the currently configured EVM are errors now.
  • SMTChecker: Do not report underflow/overflow if they always revert. This removes false positives when using SafeMath.
  • Standard JSON Interface: Allow retrieving metadata without triggering bytecode generation.
  • Standard JSON Interface: Provide fine-grained control over the optimizer via the settings.
  • Static Analyzer: Warn about expressions with custom types when they have no effect.
  • Optimizer: Add new rules with constants including LT, GT, AND and BYTE.
  • Optimizer: Add rule for shifts with constants for Constantinople.
  • Optimizer: Combine multiple shifts with constant shift-by values into one.
  • Optimizer: Do not mask with 160-bits after CREATE and CREATE2 as they are guaranteed to return an address or 0.
  • Optimizer: Support shifts in the constant optimiser for Constantinople.
  • Yul Optimizer: Add rule to replace switch statements with literals by matching case body.


  • ABIEncoderV2: Fix internal error related to bare delegatecall.
  • ABIEncoderV2: Fix internal error related to ecrecover.
  • ABIEncoderV2: Fix internal error related to mappings as library parameters.
  • ABIEncoderV2: Fix invalid signature for events containing structs emitted in libraries.
  • Inline Assembly: Proper error message for missing variables.
  • Optimizer: Fix internal error related to unused tag removal across assemblies. This never generated any invalid code.
  • SMTChecker: Fix crash related to statically-sized arrays.
  • TypeChecker: Fix internal error and disallow index access on contracts and libraries.
  • Yul: Properly detect name clashes with functions before their declaration.
  • Yul: Take built-in functions into account in the compilability checker.
  • Yul Optimizer: Properly take reassignments to variables in sub-expressions into account when replacing in the ExpressionSimplifier.

Build System:

  • Soltest: Add support for left-aligned, padded hex literals.
  • Soltest: Add support for right-aligned, padded boolean literals.

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

Download the new version of Solidity here.

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