tree 1aeef41d7c988db4d02026af31a3290e9288245f
parent 6de21f11125941ea1b94fdeec754bacea3916fd5
author Tom Cherry <tomcherry@google.com> 1503443235 -0700
committer Tom Cherry <tomcherry@google.com> 1503511472 -0700

init: pass errors from one Result<T> to another better

Result<T> currently has two problems,
1) A failing Result<T> cannot be easily constructed from a Result<U>'s
error.
2) errno is lost when passing .error() through multiple Result<T>'s

This change fixes both problems having Result<T>::error() return a
ResultError class that contains the std::string error message and int
errno.

It additionally has ostream operators to continue to allow printing
the error string directly to an ostream and also to pass the errno
through to another Result<T> class via Error() creation.

Lastly, it provides a new constructor for Result<T> for ResultError,
such that a Result<T> can be constructed from Result<U>::error().

Test: boot bullhead, init unit tests
Change-Id: Id9614b727cdabd2f5498b0da0e598e9aff7d9ae0