On Thu, May 01, 2014 at 11:07:51PM -0400, Tom Lane wrote: > Noah Misch <n...@leadboat.com> writes: > > On Thu, May 01, 2014 at 08:44:46PM -0400, Tom Lane wrote: > >> You're only considering one aspect of the problem. Yeah, you might not > >> get duplicated output unless system() prints something before exec(), > >> but we would also like to have causality: that is, whatever we sent to > >> stdout before calling system() should appear there before anything the > >> child process sends to stdout. > > > Good point. I suppose a couple of fflush() calls have negligible cost next > > to > > a system() or popen(). Introduce pg_popen()/pg_system(), and adopt a rule > > that they are [almost] our only callers of raw popen()/system()? > > Meh. I'm not usually in favor of adopting nonstandard notation, and > this doesn't seem like a place to start. In particular, if you don't > want to use fflush(NULL) in these proposed wrappers, then call sites > are still going to have an issue with needing to do manual fflushes; > pg_regress.c's spawn_process is an example: > > /* > * Must flush I/O buffers before fork. Ideally we'd use fflush(NULL) here > * ... does anyone still care about systems where that doesn't work? > */ > fflush(stdout); > fflush(stderr); > if (logfile) > fflush(logfile); > > pid = fork(); > > I think that removing the need for fflush(stdout) and fflush(stderr) > in this context would mostly result in people forgetting to fflush > other output files. I'd rather have the two lines of boilerplate > (and a comment about why we're refusing to depend on fflush(NULL)) > than take that risk.
Works for me. -- Noah Misch EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
