Telling the truth about all program behaviors collectively is hard. Can an analysis say something useful and true without making assumptions that are violated by nearly all real programs?
The purpose of a program analysis is to infer whether a certain property of a program execution can be observed at runtime. The notion of an analysis’ soundness defines how much confidence one should put in its results. The notion is not uniform and is determined by whether the analysis is intended to be used as a testing or as a verification tool.