SPLASH 2022
Mon 5 - Sat 10 December 2022 Auckland, New Zealand
Fri 9 Dec 2022 14:00 - 14:30 at AMRF Auditorium - Logic and Verification I Chair(s): Benjamin Lucien Kaminski

Many separation logics support fractional permissions to distinguish between read and write access to a heap location, for instance, to allow concurrent reads while enforcing exclusive writes. Fractional permissions extend to composite assertions such as (co)inductive predicates and magic wands by allowing those to be multiplied by a fraction. Typical separation logic proofs require that this multiplication has three key properties: it needs to distribute over assertions, it should permit fractions to be factored out from assertions, and two fractions of the same assertion should be combinable into one larger fraction.

Existing formal semantics incorporating fractional assertions into a separation logic define multiplication semantically (via models), resulting in a semantics in which distributivity and combinability do not hold for key resource assertions such as magic wands, and fractions cannot be factored out from a separating conjunction. By contrast, existing automatic separation logic verifiers define multiplication syntactically, resulting in a different semantics for which it is unknown whether distributivity and combinability hold for all assertions.

In this paper, we present a novel semantics for separation logic assertions that allows states to hold more than a full permission to a heap location during the evaluation of an assertion. By reimposing upper bounds on the permissions held per location at statement boundaries, we retain key properties of separation logic, in particular, the frame rule. Our assertion semantics unifies semantic and syntactic multiplication and thereby reconciles the discrepancy between separation logic theory and tools and enjoys distributivity, factorisability, and combinability. We have formalised our semantics and proved its properties in Isabelle/HOL.

Fri 9 Dec

Displayed time zone: Auckland, Wellington change

13:30 - 15:00
Logic and Verification IOOPSLA at AMRF Auditorium
Chair(s): Benjamin Lucien Kaminski Saarland University and University College London
13:30
30m
Research paper
Finding real bugs in big programs with incorrectness logicDistinguished Paper
OOPSLA
Quang Loc Le University College London, Azalea Raad Imperial College London, Jules Villard Meta, Josh Berdine Meta, Derek Dreyer MPI-SWS, Peter W. O'Hearn Meta; University College London
DOI
14:00
30m
Talk
Fractional Resources in Unbounded Separation LogicDistinguished Paper
OOPSLA
Thibault Dardinier ETH Zurich, Peter Müller ETH Zurich, Alexander J. Summers University of British Columbia
DOI
14:30
30m
Talk
Proving Hypersafety Compositionally
OOPSLA
Emanuele D’Osualdo MPI-SWS, Azadeh Farzan University of Toronto, Derek Dreyer MPI-SWS
DOI Pre-print