Bug#1040947: perl: readline fails to detect updated file

[Niko Tyni]

On Sun, Jul 16, 2023 at 11:35:49AM +0300, Niko Tyni wrote:
> Control: forwarded -1 https://github.com/Perl/perl5/issues/21240
> 
> On Wed, Jul 12, 2023 at 09:17:54PM +0000, Eric Wong wrote:
> > Package: perl
> > Version: 5.36.0-7
> > Severity: normal
> > Tags: upstream
> > 
> > Dear Maintainer,
> > 
> > The `readline' op (`<FH>') no longer detects updates to file
> > which is being written to in Perl 5.36.0 after updating to bookworm.
> > 
> > The attached script worked fine with Perl 5.32.1 in oldstable,
> > both scripts show the size changing with the `-s FH' op.
> > Same behavior on both amd64 and i386.
> 
> Thanks for the report.
> 
> This changed with
> 
>   https://github.com/Perl/perl5/commit/80c1f1e45e8ef8c27d170fae7ade41971fe20218
> 
> which went upstream in 5.37.4. We backported it for 5.36 to fix #1016369 .
> 
> I've forwarded it upstream as https://github.com/Perl/perl5/issues/21240

Upstream says it's a direct consequence of fixing #1016369 so
the earlier behaviour of reading after EOF was a bug.

You need to clear the EOF flag by calling $rd->clearerr() or
seek($rd, 0, SEEK_CUR) to get the appended lines.

-- 
Niko Tyni   ntyni at debian.org