Hacker News Reader

> Not every high-level language gives you byte-level access to the representation of memory objects.

Any code that ventures anywhere near that territory is 99% Undefined Behavior. It's almost impossible to write proper C/C++ code that isn't UB while touching byte-level representations.

View on HN

This is certainly not true. Accessing bytes of objects is well-defined in C.

Just look at this: https://blog.habets.se/2026/05/Everything-in-C-is-undefined-...

This is undefined behavior!

const int* magic_intp = (const int*)bytes;

Heck even something trivial like this is UB:

bool bar(char ch) { return isxdigit(ch); }

The only safe thing to do is memcpy, but that's super useless. As soon as you try to interpret or manipulate the byte-level data in any way, there are UB traps everywhere you go.

Yes, using an arbitrary type that is different from the one of the object is UB. But any access of a representation byte using a character pointer is well defined, not just memcpy and I would also not call memcpy useless.

Reply on news.ycombinator.com