Michael Paquier <michael(at)paquier(dot)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