Everything in C is undefined behavior

A 30-year C/C++ veteran argues that undefined behavior (UB) is so pervasive in C and C++ that no programmer, no matter how expert, can reliably avoid it. The post walks through numerous non-obvious UB examples: misaligned pointer access, casting uint8_t* to int*, passing char to isxdigit(), float-to-int conversion, null pointer semantics, variadic argument type mismatches, and integer promotion surprises. The author contends UB is not just a compiler optimization concern but a fundamental semantic gap — the compiler simply has no way to express the programmer's intent. The post concludes that LLMs are now better than humans at spotting UB, and that writing C/C++ in 2026 without LLM-assisted review is arguably irresponsible, citing findings in OpenBSD's codebase as evidence.