MFC r317888:
Pull in r302362 from upstream libc++ trunk (by me):
Ensure showbase does not overflow do_put buffers Summary: In https://bugs.freebsd.org/207918, Daniel McRobb describes how using std::showbase with ostreams can cause truncation of unsigned long long when output format is octal. In fact, this can even happen with unsigned int and unsigned long. To ensure this does not happen, add one additional character to the do_put buffers if std::showbase is on. Also add a test case. Reviewers: EricWF, mclow.lists Reviewed By: EricWF Subscribers: cfe-commits, emaste Differential Revision: https://reviews.llvm.org/D32670
PR: 207918