What undefined behaviour is there using the operator?

Although mimicked by many languages because of its widespread familiarity, C's syntax has been often targeted as one of its weakest points. For example, Kernighan and Ritchie say in the second edition of The C Programming Language, "C, like any other language, has its blemishes. Some of the operators have the wrong precedence; some parts of the syntax could be better." Bjarne Stroustrup said of C++ (which is superficially similar to C): "Within C++, there is a much smaller and cleaner language struggling to get out. the C++ semantics is much cleaner than its syntax." Some specific problems worth noting are: