Re: More consistency for some file-related error message

Michael Paquier <michael@paquier.xyz> writes:
> On Wed, Jul 18, 2018 at 10:57:16AM -0400, Tom Lane wrote:
>> BTW, isn't the initial "errno = 0" dead code now?

> Hm.  I have not bothered touching those as it could be possible that
> read() may not initialize errno to 0, so errno would remain set to any
> previous value when less bytes than expected are read, no?  It seems to
> me that the current coding is more careful.

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.

            regards, tom lane