Re: Cleaning up historical portability baggage

On Mon, Aug 29, 2022 at 3:13 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:

> On Mon, Aug 29, 2022 at 9:40 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Here's another bit of baggage handling: fixing up the places that
> > were afraid to use fflush(NULL). We could doubtless have done
> > this years ago (indeed, I found several places already using it)
> > but as long as we're making a push to get rid of obsolete code,
> > doing it now seems appropriate.
>
> +1, must be OK (pg_dump and pg_upgrade).
>
> Archeology:
>
> commit 79fcde48b229534fd4a5e07834e5e0e84dd38bee
> Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
> Date: Sun Nov 29 01:51:56 1998 +0000
>
> Portability fix for old SunOS releases: fflush(NULL)
>
>
> https://www.postgresql.org/message-id/199811241847.NAA04690%40tuna.uimage.com
>
> SunOS 4.x was still in some kind of support phase for a few more
> years, but I guess they weren't working too hard on conformance and
> features, given that SunOS 5 (the big BSD -> System V rewrite) had
> come out in '92...
>
> > One thing that's not clear to me is what the appropriate rules
> > should be for popen(). POSIX makes clear that you shouldn't
> > expect popen() to include an fflush() itself, but we seem quite
> > haphazard about whether to do one or not before popen(). In
> > the case of popen(..., "r") we can expect that the child can't
> > write on our stdout, but stderr could be a problem anyway.
> >
> > Likewise, there are some places that fflush before system(),
> > but they are a minority. Again it seems like the main risk
> > is duplicated or mis-ordered stderr output.
> >
> > I'm inclined to add fflush(NULL) before any popen() or system()
> > that hasn't got one already, but did not do that in the attached.
>
> Couldn't hurt. (Looking around at our setvbuf() setup to check the
> expected stream state in various places... and huh, I hadn't
> previously noticed the thing about Windows interpreting line buffering
> to mean full buffering. Pfnghghl...)
>
>
> The patch does not apply successfully; please rebase the patch.

patching file src/backend/postmaster/fork_process.c
Hunk #1 FAILED at 37.
1 out of 1 hunk FAILED -- saving rejects to file
src/backend/postmaster/fork_process.c.rej
patching file src/backend/storage/file/fd.c
Hunk #1 FAILED at 2503.
1 out of 1 hunk FAILED -- saving rejects to file
src/backend/storage/file/fd.c.rej
patching file src/backend/utils/error/elog.c
Hunk #1 FAILED at 643.
Hunk #2 FAILED at 670.

--
Ibrar Ahmed