I'm sure there have been attempts at defining a language that has no UB, but afaik all meaningful languages have UB in some dark corner or enumerated explicitly. For example, Java thread execution order is UB.

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aw1621107 2 hours ago | parent [-]

> For example, Java thread execution order is UB.

In this context "UB" means something different than how you're using it. The UB being mentioned here is the "nasal demons" form, i.e., programs which contain undefined behavior have no defined meaning according to the language semantics.

What you're talking about is probably better described in this context as "unspecified behavior", which is behavior that the language standard does not mandate but does not render programs meaningless. For example, IIRC in C++ the order in which g(), h(), and i() are evaluated in f(g(), h(), and i()) is unspecified - an implementation can pick any order, and the order doesn't have to be consistent, but no matter the order the program is valid (approximately speaking).

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repelsteeltje 2 hours ago | parent [-]

Great example.

So this "unspecified behavior" might turn into the more nasal demon type when g(), h() and i() share mutable state and assume some particular sequential order of execution. No?

	▲	fc417fc802 18 minutes ago \| parent \| next [-]
		That would depend entirely on the assumptions being made and the constructs being used. I think in most cases it would likely just result in regular garden variety bugs. But sure, if you're writing C++ and (for example) g is depended on for initialization of pointed memory that the other two consume you could end up with UB. But if you're writing Java then no, you will not end up with UB just buggy code.
	▲	aw1621107 44 minutes ago \| parent \| prev [-]
		Not necessarily. Unspecified behavior and undefined behavior are independent concepts; a language can have one but not the other. As a result, you can have languages where incorrect reliance on unspecified behavior can lead to undefined behavior (e.g., C and C++) and languages where incorrect reliance on unspecified behavior can lead to bugs, but not nasal demons (e.g., Java)