Integer Overflow Interview Question - Salesforce Prep

What the question covers

You’ll be asked to explain and analyze integer overflow and underflow: how values exceed storage limits (e.g., 32-bit, 64-bit), language-specific behavior, and real-world consequences like crash or security flaws. Expect code snippets in C/C++ or Java where you must spot overflow risks (wraparound vs. undefined behavior) and propose fixes.

Typical interview flow

1. Clarify assumptions (signed vs unsigned, width of types, target language).
2. Read and reason about a short code example (arithmetic, buffer size calc, or loop).
3. Demonstrate detection strategies and write a safe alternative or checks.
4. Discuss trade-offs, performance, and security implications.

Skills and signals the interviewer looks for

You should show: understanding of fixed-width types (INT32_MAX/INT64_MAX), that C/C++ signed overflow is undefined while Java wraps, knowledge of safe patterns (bounds checking, use of wider types, saturation arithmetic), and practical tools (static analysis, -fsanitize=undefined, __builtin_add_overflow, BigInteger/BigInt, SafeInt libraries). Call out common pitfalls: mixing signed/unsigned, using size_t for allocation without checks, and integer-to-pointer conversions that enable exploits.

How to prepare and practice

Analyze snippets: add preconditions (check before add/multiply), promote types before arithmetic, use compiler sanitizers and unit tests, and write small helper functions (checked_add, checked_mul) using compiler intrinsics. Practice explaining the security impact (allocation size overflow → buffer overflow) and trade-offs between correctness and performance.