Re: Obsolete coding in fork_process.c

I wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
>> On Thu, May 01, 2014 at 12:13:28PM -0400, Tom Lane wrote:
>>> Is there any reason not to change this to just fflush(NULL)? We dropped
>>> support for SunOS 4.1 quite some time ago ...

>> Modern systems have other fflush(NULL) problems:

>> http://www.nntp.perl.org/group/perl.perl5.porters/2013/09/msg207692.html
>> http://perl5.git.perl.org/metaconfig.git/blob/master:/U/perl/fflushall.U

> Fun. I doubt that the postmaster's stdin would ever be a pipe, but
> maybe we'd better leave well enough alone. Should update the comment
> though.

However ... after looking around I notice that fflush(NULL) is already
being used in parallel pg_dump and pg_upgrade; and at least in the latter
case I'm afraid to change that because it looks like there are probably
other stdio output files open in the process.

I think we should probably go ahead and switch over to using
fflush(NULL). The capability is required by C89 for crissake;
are we really going to rely on hearsay evidence that there are
current platforms that are still broken? Also, I found at least
one claim on the net that this has been fixed in Solaris for awhile:
http://grokbase.com/t/perl/perl5-porters/021hn4z9pq/fflush-null-on-solaris-9

Attached is a draft patch that I was working on before I decided that
making the indicated changes in pg_upgrade was probably a bad idea.
This is mainly to memorialize the places we should look at if we
change it.

BTW, while working on this I noticed that there are a boatload of places
where we use system() or popen() without a prior fflush. I suspect most
of them are safe, or we'd have heard more complaints --- but shouldn't
we clamp down on that?

regards, tom lane