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
MFC after: 3 days
5ffea91ec5