When Long Jumps Fall Short: Control-Flow Tracking and Misuse Detection for Non-local Jumps in C
Michael H. Schwarz, Julian Erhard, Vesal Vojdani, Simmo Saan, Helmut Seidl · 2023
The C programming language offers setjmp/longjmp as a mechanism for non-local control flow. This mechanism has complicated semantics. As most developers do not encounter it day-to-day, they may be unfamiliar with all its intricacies – leading to subtle programming errors. At the same time, most static analyzers lack proper support, implying that otherwise sound tools miss whole classes of program deficiencies. We propose an approach for lifting existing interprocedural analyses to support setjmp/longjmp, as well as to flag their misuse. To deal with the non-local semantics, our approach leverages side-effecting transfer functions which, when executed, may trigger contributions to extra program points. We showcase our analysis on real-world examples and propose a set of litmus tests for other analyzers.