DetectThrowsException Decision Problem

Anoop Guragain, Duru Akbas, Joseph Oforkansi

September 8, 2025

Introduction

A simple exceptions “detection” program

• Takes an input that is a string containing source code
• Search through the source code line by line using regex for certain keys or pattern
• Add those lines that matches to a list called “warnings” with a message
• Convert that list into multi-line string and returns it

To be noted

• It does not detect, it just kind of predicts if the program is going to throw an exception.

• It does not run the program or confirms that an exception will or won’t occur.

• It gives false positive and false negative such as it count comments and strings as the part of the source code

Exceptions

• Divisible by zero

 if re.search(r"/\s*0", line):
    warnings.append(f"Division by zero at line {i}")

• Value error (int() and float())

  if "int(" in line or "float(" in line:
    warnings.append(f"Possible ValueError in conversion at line {i}")

• Index error

  if re.search(r"\w+\[.*\]", line):
    warnings.append(f"Possible IndexError/KeyError at line {i}")

• Raise

  if "raise " in line:
    warnings.append(f"Explicit raise at line {i}")

Output

• detect_exceptions function scans for risky patterns
• Splits “code” into individual lines
• Exception triggers are: division by zero, type conversions, indexing or dictionary access (opening and closing brackets and matches a word), explicit raise statements
• Returns the warnings found

Conclusion

• Heuristic detection: 🟢 Our DetectThrowsException program is a heuristic demonstration of a decision problem. It cannot prove whether an exception will occur, but it offers a first step by flagging suspicious patterns in source code.
• Theoretical limits: ⚠️ This limitation connects to a fundamental idea in theoretical computer science: undecidability. Just as the halting problem shows no program can universally decide if another program will halt, no tool can perfectly predict all possible runtime exceptions
• Practical Value: 💡 While imperfect, our detector shows how even a simple pattern-matching approach can still provide practical value in software development, helping catch likely errors early without guaranteeing complete correctness.

What Our Detector Can and Cannot Do

✅ Can Do	❌ Cannot Do
Detect simple patterns with regex (e.g., /0, int("abc"), raise)	Prove with certainty that exceptions will (or won’t) occur
Flag likely sources of runtime errors early	Account for user input, runtime values, or complex program logic
Provide a practical, lightweight heuristic	Solve the general problem (undecidable, like the halting problem)

Key takeaway: A simple heuristic can still make a meaningful impact in software development, despite theoretical limits.

Thank You