Library Abstraction for C / C + + Concurrency — extended version —

When constructing complex concurrent systems, abstraction is vi-tal: programmers should be able to reason about concurrent li-braries in terms of abstract specifications that hide the implementa-tion details. Relaxed memory models present substantial challengesin this respect, as libraries need not provide sequentially consistentabstractions: to avoid unnecessary synchronisation, they may allowclients to observe relaxed memory effects, and library specifica-tions must capture these.In this paper, we propose a criterion for sound library abstrac-tion in the new C11 and C++11 memory model, generalising thestandard sequentially consistent notion of linearizability. We provethat our criterion soundly captures all client-library interactions,both through call and return values, and through the subtle syn-chronisation effects arising from the memory model. To illustrateour approach, we verify implementations against specifications forthe lock-free Treiber stack and a producer-consumer queue. Oursis the first approach to compositional reasoning for concurrentC11/C++11 programs.