Re: More consistency for some file-related error message

On Thu, Jul 19, 2018 at 12:33:30PM +0900, Michael Paquier wrote:
> On Wed, Jul 18, 2018 at 11:24:05PM -0400, Tom Lane wrote:
>> read() is required by spec to set errno when returning a negative result.
>> I think the previous coding paid attention to errno regardless of the sign
>> of the result, which would justify pre-zeroing it ... but the new coding
>> definitely doesn't.
> 
> Yes, my point is a bit different though..  Do you think that we need to
> bother about the case where errno is not 0 before calling read(), in the
> case where it returns a positive result?  This would mean that errno
> would still have a previous errno set, still it returned a number of
> bytes read.  For the code paths discussed here that visibly does not
> matter so you are right, we could remove them, still patterns get easily
> copy-pasted around...

Okay, I just looked again at this point, and among the new messages only
what's in XLogFileCopy has been bothering setting errno to 0 (see
811b6e3), so let's remove it in this case.

Thoughts about the previous patch set?
--
Michael