This paper presents a generalization of standard effect systems that we call contextual effects. A traditional effect system computes the effect of an expression e. Our system additionally computes the effects of the computational context in which e occurs: both the effect of the computation that has already occurred (prior effects) and the effect of the computation yet to take place (future effects).
Contextual effects can be used in any application in which the past or future computation of the program is relevant at various program points. We present two substantial examples. First, we show how prior and future effects can be used to enforce transactional version consistency (TVC), a novel correctness property for dynamic software updates. TVC ensures that programmer-designated transactional code blocks appear to execute entirely at the same code version, even if a dynamic update occurs in the middle of the block. Second, we show how future effects can be used in the analysis of multi-threaded programs to find thread-shared locations. This is an essential step in applications such as data race detection.
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@INPROCEEDINGS{neamtiu08context,
AUTHOR = {Iulian Neamtiu and Michael Hicks and Jeffrey S. Foster and Polyvios Pratikakis},
TITLE = {Contextual Effects for Version-Consistent Dynamic Software Updating and Safe Concurrent Programming},
BOOKTITLE = {Proceedings of the {ACM} Conference on Principles of Programming Languages (POPL)},
PAGES = {37--49},
MONTH = JAN,
YEAR = 2008
}