CATCHING BUGS IN THE WEB OF PROGRAM INVARIANTS

MrSpidey is a user-friendly, interactive static debugger for Scheme. A static debugger supplements the standard debugger by analyzing the pr ogram and pinpointing those program operations that may cause run-time errors such as dereferencing the null pointer or applying non-functio ns. The program analysis of MrSpidey computes value set descriptions f or each term in the program and constructs a value flow graph connecti ng the set descriptions. Using the set descriptions, MrSpidey can iden tify and highlight potentially erroneous program operations, whose cau se the programmer can then explore by selectively exposing portions th e value flow graph.