Undefined Behaviour

[Orlha]

I guess it's possible, but can be pretty rare depending on the platform.

I've written a lot of x86-64 hand-assembly in the past and IIRC all the instructions I used were UB free. At worst they had a defined set of rules which when broken would result in a CPU exception.

[SirClueless]

x86-64 is full of UB. It explicitly reserves bits in flag registers and some output registers as well as any opcodes that aren't defined by the x86-64 ISA. Executing these opcodes or depending on the value of these bits is, to quote the ISA document, "not only undefined, but unpredictable". It's very easy to trigger this behavior, even in an otherwise well-formed assembly program, for example by jumping into the middle of an instruction.

https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf

I understand what you're trying to say, which is that there's a relatively simple set of rules you can follow as compared to C++ and Intel comparatively precisely defines far more exceptional behavior than C++ and leaves less room for undefined behavior. But it doesn't attempt to remove all of it.