Daniel Gustafsson <daniel(at)yesql(dot)se> writes:
> Agreed, zero should be valid as it's a non-negative integer. However, callers
> in fd.c are themselves checking for (fd <= 0) in some cases, and some have done
> so since the very early days of the codebase, so I wonder if there historically
> used to be a platform which considered 0 an invalid fd?
I'm betting it's a thinko that never got caught because 0 would
always be taken up by stdin. Maybe you'd notice if you tried to
close-and-reopen stdin, but that's not something the server ever does.
regards, tom lane