The Complex Approach of the C-lightVer System to the Automated Error Localization in C-Programs

The C-lightVer system for the deductive verification of C-programs is developed at the A.P. Ershov Institute of Informatics Systems of the Siberian Branch of the Russian Academy of Sciences. The C-light input language is translated into the intermediate C-kernel language based on the two-level architecture of the system. The C-kernel program and Hoare logic for the C-kernel are the input of the metagenerator. The definite iteration approach is used to solve the well-known problem of defining loop invariants. The body of a definite iteration loop is executed once for each element of the finite dimensional data structure, and the inference rule for them uses the replacement operation rep, which represents the action of the loop in a symbolic form. Also, the method of semantic labeling of verification conditions is implemented and extended in our metagenerator. This makes it possible to generate explanations for unproven conditions and simplifies error localization. Finally, if the ACL2 system fails to prove a verification condition, it is possible to focus on proving that it is false. Previously, we developed a method for checking the falsity of verification conditions for the ACL2 system. The need for more detailed explanations of the verification conditions containing the replacement operation rep has led to changes in the algorithms for generating the replacement operation, extracting semantic labels, and generating explanations for unproven verification conditions. The article presents modifications of these algorithms. These modifications make it possible to mark the source code of the rep function with semantic labels, extract semantic labels from the rep definition, and generate a description of the break statement execution condition.