This is undefined behavior, but glibc and macOS are both lenient, and
someone hit this in the wild, so we may as well be lenient too. (The
only cost is that it's now slightly easier to write code that works on
everything except old versions of Android.)
Bug: https://issuetracker.google.com/180598400
Test: treehugger
Change-Id: Ia217169ea6283cc53f4fbf71e5abfa08356c2049