Optimization Flags

Tencent Database Technology

Dec 20, 2018 · Fundamentals

Unexpected Behavior with -O2 Optimization Due to Strict Aliasing Violations in C++

The article explains why a C++ program produces different outputs with and without the -O2 optimization flag, tracing the issue to strict aliasing violations caused by type‑punning pointer casts, and shows how disabling -fstrict-aliasing or using -fno‑strict‑aliasing resolves the problem.