Make sure we appropriately retry calls to read if the return result is
less than what we asked for.
Additionally, check and handle IO errors: EINTR results in the read
operation getting restarted; other errors turn into exceptions.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@210061 91177308-0d34-0410-b5e6-96231b3b80d8
random_device::random_device(const string&) wrongly assumes that open
can only validly return a file descriptor greater than zero.
This results in random_device believing that it didn't successfully open
the device causing it to throw in it's constructor, this ends up leaking
a file descriptor.
The fix is simple, don't error on file descriptors which are zero.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@210060 91177308-0d34-0410-b5e6-96231b3b80d8
