alt Hacker NewsI think it's common to be taught that UB is very bad when you're new, partly to simplify your debugging experience, partly to help you understand and mentally demarcate the boundaries of what the language allows and doesn't allow, and partly because there are many Standards-Purists who genuinely avoid UB. But from my own experience, UB just means "consult your compiler to see what it does here because this question is beyond our pay grade."
Interestingly enough, and only semi related, I had to use volatile for the first time ever in my latest project. Mainly because I was writing assembly that accessed memory directly, and I wanted to make sure the compiler didn't optimize away the variable. I think that's maybe the last C keyword on my bucket list.
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> But from my own experience, UB just means "consult your compiler to see what it does here because this question is beyond our pay grade."
Careful. It's not just "consult your compiler", because the behavior of a given compiler on code containing UB is also allowed to vary based on specific compiler version, and OS, and hardware, and the phase of the moon.
> But from my own experience, UB just means "consult your compiler to see what it does here because this question is beyond our pay grade."
People are taught it’s very bad because otherwise they do exactly this, which is the problem. What does your compiler do here may change from invocation to invocation, due to seemingly unrelated flags, small perturbations in unrelated code, or many other things. This approach encourages accepting UB in your program. Code that invokes UB is incorrect, full stop.