Optimization Levels

Optimization levels, set with compiler flags like -O0 through -O3 in GCC and Clang, control how aggressively the compiler transforms code to improve performance, often at the cost of longer compile times and less predictable debugging behavior. -O0 disables optimization entirely, which is useful during development since the compiled code closely matches the source. Higher levels can reorder, inline, or eliminate code in ways that make step-by-step debugging harder to follow, and can also expose undefined behavior that seemed to work correctly at lower optimization levels.