No, it was implementation defined, which is very different. Every implementation you were ever likely to encounter defined it reasonably. Making some of it undefined now has created a bunch of code that uses macros to cast back and forth between unsigned to get the expected behavior (or, for cases where it is provable that the result is representable, to replace the left shift with a multiplication and hope the optimizing compiler translates it back, because compilers now warn on any left shift of a negative value, despite the fact that the semantics are supposed to be the same as the corresponding multiplication now).

In other words, it created a mess for basically no reason.