Re: dup(0) fails on Ubuntu 20.04 and macOS 10.15 with 13.0

Mario Emmenlauer <mario@emmenlauer.de> writes:
> The idea to switch to dup(2) sounds very good to me.

I poked at this some more, and verified that adding "fclose(stdin);"
at the head of PostmasterMain is enough to trigger the reported
failure.  However, after changing fd.c to dup stderr not stdin,
we can pass check-world even with that in place.  So that confirms
that there is no very good reason for the postmaster to require
stdin to be available.

Hence, I pushed the fix to make fd.c use stderr here.  I only
back-patched to v14, because given the lack of other complaints,
I couldn't quite justify touching stable branches for this.

            regards, tom lane