Re: cat-file timing window on Cygwin

[Adam Dinwoodie <adam@dinwoodie.org>]

On Sat, Aug 26, 2017 at 11:53:37AM -0700, Jeff King wrote:
> On Sat, Aug 26, 2017 at 01:57:18AM +0100, Ramsay Jones wrote:
> 
> > > diff --git a/run-command.c b/run-command.c
> > > index 98621faca8..064ebd1995 100644
> > > --- a/run-command.c
> > > +++ b/run-command.c
> > > @@ -641,7 +641,6 @@ int start_command(struct child_process *cmd)
> > >  	}
> > >  
> > >  	trace_argv_printf(cmd->argv, "trace: run_command:");
> > > -	fflush(NULL);
> > >  
> > >  #ifndef GIT_WINDOWS_NATIVE
> > >  {
> > 
> > I suspect not, but I can give it a try ...
> > 
> > ... oh, wow, that works! Ahem. (Hmm, so it's flushing stdin?!)
> 
> Interesting. I find it a little hard to believe there's so obvious a bug
> as "fflush(NULL) flushes stdin", but well...that's what it seems like.
> 
> If that's truly what it is, this is the minimal reproduction I came up
> with:
> 
> -- >8 --
> #include <stdio.h>
> 
> int main(void)
> {
> 	char buf[256];
> 	while (fgets(buf, sizeof(buf), stdin)) {
> 		fprintf(stdout, "got: %s", buf);
> 		fflush(NULL);
> 	}
> 	return 0;
> }
> -- 8< --
> 
> If this really is the bug, then doing something like "seq 10 | ./a.out"
> would drop some of the input lines.

...yep.  It does.  Specifically, I consistently only get the firsts
line:

    $ seq 10 | ./a.exe
    got: 1
    
    $ 

If I introduce a delay between the lines of stdin (which I tested by
just typing stdin from the keyboard), it works as expected.

Looks like this one will need to go to the Cygwin mailing list; I'll
take it there shortly.  Thank you all for your help getting this far!