A Program Logic for Dependence Analysis

Bubel, Richard; Hähnle, Reiner; Tabar, Asmae Heydari

doi:10.1007/978-3-030-34968-4_5

Cited by 6 publications

(4 citation statements)

References 23 publications

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“…Future Work. For formalized parallelization of C code, we plan to integrate a formal, logic-based dependences analysis [10] and to consider further cases of underspecification of a larger fragment of C, e.g., in list initializers. The newest version of C2ABS uses different model extraction strategies [38] and we will investigate using Crowbar to verify these models as well.…”

Section: Discussionmentioning

confidence: 99%

The Right Kind of Non-Determinism: Using Concurrency to Verify C Programs with Underspecified Semantics

Kamburjan

Wasser²

2022

Electron. Proc. Theor. Comput. Sci.

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We present a novel and well automatable approach to formal verification of C programs with underspecified semantics, i.e., a language semantics that leaves open the order of certain evaluations. First, we reduce this problem to non-determinism of concurrent systems, automatically extracting a distributed Active Object model from underspecified, sequential C code. This translation process provides a fully formal semantics for the considered C subset. In the extracted model every non-deterministic choice corresponds to one possible evaluation order. This step also automatically translates specifications in the ANSI/ISO C Specification Language (ACSL) into method contracts and object invariants for Active Objects. We then perform verification on the specified Active Objects model, using the Crowbar theorem prover, which verifies the extracted model with respect to the translated specification and ensures the original property of the C code for all possible evaluation orders. By using model extraction, we can use standard tools, without designing a new complex program logic to deal with underspecification. The case study used is highly underspecified and cannot be handled correctly by existing tools for C.

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Section: Discussionmentioning

confidence: 99%

The Right Kind of Non-Determinism: Using Concurrency to Verify C Programs with Underspecified Semantics

Kamburjan

Wasser²

2022

Electron. Proc. Theor. Comput. Sci.

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show abstract

“…Future Work. For formalized parallelization of C code, we plan to integrate a formal, logic-based dependences analysis [10] and to consider further cases of underspecification of a larger fragment of C, e.g., in list initializers. The newest version of C2ABS uses different model extraction strategies [40] and we will investigate using Crowbar to verify these models as well.…”

Section: Discussionmentioning

confidence: 99%

“…Underspecified behavior lurks at every binary operation 10 and can have subtle effects in larger systems. To evaluate our verification approach, we use an extreme case of underspecification, investigating the C program 11 in Fig.…”

Section: Case Studymentioning

confidence: 99%

“…8 containing a function whose result heavily depends on unspecified evaluation order. The function in question is declared as int one_to_fib(int n) and should calculate 10 Underspecified behavior also lurks at many function calls. 11 Adapted from an idea on Derek Jones's The Shape of Code blog at: shape-of-code.coding-guidelines.com/2011/06/18/fibonacci-and-jit-compilers/ //@ ABS def Int fib(Int n) = if n <= 2 then 1 //@ else fib(n−1) + fib(n−2); / * @ strong global invariant x == 0 || x == 1; @ * / int x;…”

Section: Case Studymentioning

confidence: 99%

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Deductive Verification of Programs with Underspecified Semantics by Model Extraction

Kamburjan¹,

Wasser²

2021

Preprint

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We present a novel and well automatable approach to formal verification of programs with underspecified semantics, i.e., a language semantics that leaves open the order of certain evaluations. First, we reduce this problem to non-determinism of distributed systems, automatically extracting a distributed Active Object model from underspecified, sequential C code. This translation process provides a fully formal semantics for the considered C subset. In the extracted model every nondeterministic choice corresponds to one possible evaluation order. This step also automatically translates specifications in the ANSI/ISO C Specification Language (ACSL) into method contracts and object invariants for Active Objects. We then perform verification on the specified Active Objects model. For this we have implemented a theorem prover Crowbar based on the Behavioral Program Logic (BPL), which verifies the extracted model with respect to the translated specification and ensures the original property of the C code for all possible evaluation orders. By using model extraction, we can use standard tools, without designing a new complex program logic to deal with underspecification. The case study used is highly underspecified and cannot be verified with existing tools for C.

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Correct program parallelisations

Blom¹,

Darabi

Huisman

et al. 2021

Int J Softw Tools Technol Transfer

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A commonly used approach to develop deterministic parallel programs is to augment a sequential program with compiler directives that indicate which program blocks may potentially be executed in parallel. This paper develops a verification technique to reason about such compiler directives, in particular to show that they do not change the behaviour of the program. Moreover, the verification technique is tool-supported and can be combined with proving functional correctness of the program. To develop our verification technique, we propose a simple intermediate representation (syntax and semantics) that captures the main forms of deterministic parallel programs. This language distinguishes three kinds of basic blocks: parallel, vectorised and sequential blocks, which can be composed using three different composition operators: sequential, parallel and fusion composition. We show how a widely used subset of OpenMP can be encoded into this intermediate representation. Our verification technique builds on the notion of iteration contract to specify the behaviour of basic blocks; we show that if iteration contracts are manually specified for single blocks, then that is sufficient to automatically reason about data race freedom of the composed program. Moreover, we also show that it is sufficient to establish functional correctness on a linearised version of the original program to conclude functional correctness of the parallel program. Finally, we exemplify our approach on an example OpenMP program, and we discuss how tool support is provided.

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A Program Logic for Dependence Analysis

Cited by 6 publications

References 23 publications

The Right Kind of Non-Determinism: Using Concurrency to Verify C Programs with Underspecified Semantics

The Right Kind of Non-Determinism: Using Concurrency to Verify C Programs with Underspecified Semantics

Deductive Verification of Programs with Underspecified Semantics by Model Extraction

Correct program parallelisations

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