Re: [patch, libgfortran] PR31052 Bad IOSTAT values when readings NAMELISTs past EOF

[Jerry DeLisle <jvdelisle at verizon dot net>]

Brooks Moses wrote:
> Jerry DeLisle wrote:
> > Steve Kargl wrote:
> > > I haven't read the PR nor your patch.  But, if
> > > someone is trying to rewind /dev/null, he/she
> > > is an idiot.  If it was me, I'd close the PR
> > > with a rather biting comment about stupidity.
> >
> > Easy guy, its the existing dev_null.f90 in gfortran.dg thats doing 
> > this rewind.   If you suggest we get rid of the rewind in there, then 
> > patching this PR is simply delete the call to test_endfile in st_rewind.
>
> I suspect /dev/null there is acting as a proxy for other sources that 
> also can't be rewound, but can't be easily tested in a testcase.
>
> I've certainly written codes that did rewinds which weren't obviously 
> necessary from the end-user standpoint, and I could certainly imagine an 
> unknowing user (or a forgetful user, if the user was me) hooking them up 
> to some source -- a named pipe, say -- which didn't support rewinding. 
> I'd be a bit annoyed if GFortran didn't handle that with a reasonable 
> error/IOSTAT result.
>
> Thus, if you remove this from dev_null.f90, I'd want to recommend 
> checking to make sure that you're _only_ breaking /dev/null and not 
> breaking other non-rewindable sources, and ideally make sure that this 
> is still tested some other way in the testsuite.
>
> - Brooks
I would rather keep the patch as I have it and leave dev_null.f90 alone.  In 
this case we are user proofing.  st_rewind is simply seeking to position zero of 
the file and then resetting all the internal libgfortran accounting stuff. 
/dev/null is a "special seekable" file.

I have also tested this on an empty file and it works OK for that.  The 
adjustment in the patch occurs well after all the rewind stuff is done.

I will await approval.

Thanks,

Jerry