Mutatis mutandis: Safe and predictable dynamic software updating

Gareth Stoyle, Michael Hicks, Gavin Bierman, Peter Sewell, Iulian Neamtiu

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Dynamic software updates can be used to fix bugs or add features to a running program without downtime. Essential for some applications and convenient for others, low-level dynamic updating has been used for many years. Perhaps surprisingly, there is little high-level understanding or language support to help programmers write dynamic updates effectively. To bridge this gap, we present Proteus, a core calculus for dynamic software updating in C-like languages that is flexible, safe, and predictable. Proteus supports dynamic updates to functions (even active ones), to named types and to data, allowing on-line evolution to match source-code evolution as we have observed it in practice. We ensure updates are type-safe by checking for a property we call "con-freeness" for updated types t at the point of update. This means that non-updated code will not use t concretely beyond that point (concrete usages are via explicit coercions) and thus t's representation can safely change. We show how con-freeness can be enforced dynamically for a particular program state. We additionally define a novel and efficient static updateability analysis to establish con-freeness statically, and can thus automatically infer program points at which all future (well-formed) updates will be type-safe. We have implemented our analysis for C and tested it on several well-known programs.

Original languageEnglish (US)
Pages (from-to)183-194
Number of pages12
JournalACM SIGPLAN Notices
Volume40
Issue number1
DOIs
StatePublished - Jan 1 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Software
  • Computer Graphics and Computer-Aided Design

Keywords

  • Capability
  • Dynamic software updating
  • Proteus
  • Type inference
  • Updateability analysis

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