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ISSTA 2021
Mon 12 - Fri 16 July 2021 Online
co-located with ECOOP and ISSTA 2021

Stable object identity and shared mutable state are two powerful principles in programming. The ability to create multiple aliases to mutable data allows a direct modelling of sharing that occurs naturally in a domain, and lies at the heart of efficient programming patterns where aliases provide shortcuts to key places in a data structure. However, aliasing is also the cause of low-level bugs which are notoriously hard to debug, where a change through one alias may cause unforeseen changes visible through another alias. These problems are exacerbated in a concurrent setting, where aliasing is at the root of data races with multiple threads mutating shared memory simultaneously.

Coping with pointers, aliasing and the proliferation of shared mutable state is a problem that crosscuts the software development stack, from compilers and runtimes to bug-finding tools and end-user software. They complicate modular reasoning and program analysis, efficient code generation, efficient use of memory, and obfuscate program logic.

Several techniques have been introduced to describe and reason about stateful programs, and to restrict, analyze, and prevent aliases. These include various forms of ownership types, capabilities, separation logic, linear logic, uniqueness, sharing control, escape analysis, argument independence, read-only references, linear references, effect systems, and access control mechanisms. These tools have found their way into type systems, compilers and interpreters, runtime systems and bug-finding tools.

IWACO 2021 will focus on these techniques, on how they can be used to reason about stateful (sequential or concurrent) programs, and how they have been applied to programming languages.