POD: sysseek #15438

p5pRT · 2016-07-12T09:56:05Z

Migrated from rt.perl.org#128607 (status was 'resolved')

Searchable as RT128607$

p5pRT · 2016-07-12T09:56:05Z

From niczero@wow.com

This is a bug report for perl from niczero@wow.com,
generated with the help of perlbug 1.40 running under perl 5.24.0.

The POD for sysseek [perldoc -f sysseek] appears to me to have an
error. In the second stanza it says

Note the in bytes: even if the filehandle has been set to operate
on characters (for example by using the ":encoding(utf8)" I/O
layer), "tell" will return byte offsets, not character offsets
(because implementing that would render "sysseek" unacceptably
slow).

Where it says "tell" I think it should say "sysseek". I suspect
it shouldn't mention 'tell' at all, other than in the following
stanza.

Flags:
category=docs
severity=low

Site configuration information for perl 5.24.0:

Configured by root at Mon May 16 22:00:30 BST 2016.

Summary of my perl5 (revision 5 version 24 subversion 0) configuration:

Platform:
osname=linux, osvers=3.16.0-4-amd64, archname=x86_64-linux
uname='linux dbdev 3.16.0-4-amd64 #1 smp debian 3.16.7-ckt20-1+deb8u4 (2016-02-29) x86_64 gnulinux '
config_args='-des'
hint=recommended, useposix=true, d_sigaction=define
useithreads=undef, usemultiplicity=undef
use64bitint=define, use64bitall=define, uselongdouble=undef
usemymalloc=n, bincompat5005=undef
Compiler:
cc='cc', ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2',
optimize='-O2',
cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
ccversion='', gccversion='4.9.2', gccosandvers=''
intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678, doublekind=3
d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16, longdblkind=3
ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
alignbytes=8, prototype=define
Linker and Libraries:
ld='cc', ldflags =' -fstack-protector-strong -L/usr/local/lib'
libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
libs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
libc=libc-2.19.so, so=so, useshrplib=false, libperl=libperl.a
gnulibc_version='2.19'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'

@INC for perl 5.24.0:
/usr/local/lib/site_perl/x86_64-linux
/usr/local/lib/site_perl
/opt/perl/5.24.0/lib/x86_64-linux
/opt/perl/5.24.0/lib
.

Environment for perl 5.24.0:
HOME=/home/nsandfield
LANG=en_GB.UTF-8
LANGUAGE=en_GB:en
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=/usr/local/bin:/opt/perl/5.24.0/bin:/usr/bin:/bin
PERL_BADLANG (unset)
PERL_MB_OPT=--install_base /opt/perl/5.24.0
PERL_MM_OPT=INSTALL_BASE=/opt/perl/5.24.0
SHELL=/bin/bash

p5pRT · 2016-07-12T13:55:14Z

From @dcollinsn

Introduced in 9124316, I agree that this is a typo (copy/pasted from other docs that were also added in that commit).

p5pRT · 2016-07-12T13:55:14Z

The RT System itself - Status changed from 'new' to 'open'

p5pRT · 2016-07-12T13:59:18Z

From @jkeenan

On Tue Jul 12 02:56:05 2016, niczero@wow.com wrote:

This is a bug report for perl from niczero@wow.com,
generated with the help of perlbug 1.40 running under perl 5.24.0.

-----------------------------------------------------------------
The POD for sysseek [perldoc -f sysseek] appears to me to have an
error. In the second stanza it says

Note the in bytes: even if the filehandle has been set to operate
on characters (for example by using the ":encoding(utf8)" I/O
layer), "tell" will return byte offsets, not character offsets
(because implementing that would render "sysseek" unacceptably
slow).

Where it says "tell" I think it should say "sysseek". I suspect
it shouldn't mention 'tell' at all, other than in the following
stanza.

The text here is almost identical to a paragraph also found in pod/perlfunc.pod for 'tell' (perldoc -f tell). I'm pinging the last committer to this section of the code to investigate.

Thank you very much.

--
James E Keenan (jkeenan@cpan.org)

p5pRT · 2016-07-12T19:50:21Z

From zefram@fysh.org

via RT wrote:

Note the in bytes: even if the filehandle has been set to operate
on characters (for example by using the ":encoding(utf8)" I/O
layer), "tell" will return byte offsets, not character offsets
(because implementing that would render "sysseek" unacceptably
slow).

Where it says "tell" I think it should say "sysseek".

No, it really does mean "tell", but the wording is a bit awkward.
It's obviously been copied from the equivalent paragraph in the "seek"
doc, and that seems to have been copied from the equivalent for "tell",
where it fits rather better. Note that it's referring to a function
*returning* a byte offset, which "tell" relevantly does. "sysseek"
also returns an offset, but that isn't discussed (and so isn't relevant)
until the last paragraph of this doc.

-zefram

p5pRT · 2016-07-12T20:58:54Z

From @mauke

On Tue Jul 12 02:56:05 2016, niczero@wow.com wrote:

The POD for sysseek [perldoc -f sysseek] appears to me to have an
error. In the second stanza it says

Note the in bytes: even if the filehandle has been set to operate
on characters (for example by using the ":encoding(utf8)" I/O
layer), "tell" will return byte offsets, not character offsets
(because implementing that would render "sysseek" unacceptably
slow).

Where it says "tell" I think it should say "sysseek". I suspect
it shouldn't mention 'tell' at all, other than in the following
stanza.

I agree. Fixed in 6d451ee.

p5pRT · 2016-07-12T21:21:15Z

From @dcollinsn

Are you sure? Did you see Zefram's reply?

On Tue, Jul 12, 2016 at 4:58 PM, l.mai@web.de via RT <
perlbug-followup@perl.org> wrote:

On Tue Jul 12 02:56:05 2016, niczero@wow.com wrote:

The POD for sysseek [perldoc -f sysseek] appears to me to have an
error. In the second stanza it says

Note the in bytes: even if the filehandle has been set to operate
on characters (for example by using the ":encoding(utf8)" I/O
layer), "tell" will return byte offsets, not character offsets
(because implementing that would render "sysseek" unacceptably
slow).

Where it says "tell" I think it should say "sysseek". I suspect
it shouldn't mention 'tell' at all, other than in the following
stanza.

I agree. Fixed in 6d451ee.

---
via perlbug: queue: perl5 status: open
https://rt-archive.perl.org/perl5/Ticket/Display.html?id=128607

p5pRT · 2016-07-13T03:21:55Z

From @ap

* l.mai@web.de via RT <perlbug-followup@perl.org> [2016-07-12 23:00]:

I agree. Fixed in 6d451ee.

I don’t like this edit. I propose to instead change all 3 instances of
that paragraph in perlfunc to the following:

Note the emphasis on bytes: even if the filehandle has been set to operate
on characters (for example using the C<:encoding(utf8)> I/O layer), the
L<C<seek>|/seek FILEHANDLE,POSITION,WHENCE>,
L<C<tell>|/tell FILEHANDLE>, and
L<C<sysseek>|/sysseek FILEHANDLE,POSITION,WHENCE>
family of functions use byte offsets, not character offsets,
because seeking to a character offset would be very slow in a UTF-8 file.

Pushed to ap/seektell so people can look at how the result looks&feels.

Regards,
--
Aristotle Pagaltzis // <http://plasmasturm.org/>

p5pRT · 2016-07-13T13:01:26Z

From zefram@fysh.org

Aristotle Pagaltzis wrote:

                   I propose to instead change all 3 instances of

that paragraph in perlfunc to the following:

I like this proposed version.

-zefram

p5pRT · 2016-07-13T14:08:45Z

From @xsawyerx

On 07/13/2016 05:21 AM, Aristotle Pagaltzis wrote:

* l.mai@web.de via RT <perlbug-followup@perl.org> [2016-07-12 23:00]:

I agree. Fixed in 6d451ee.
I don’t like this edit. I propose to instead change all 3 instances of
that paragraph in perlfunc to the following:

I think this phrasing is much clearer.

p5pRT · 2016-07-13T15:03:17Z

From @ap

* Aristotle Pagaltzis <pagaltzis@gmx.de> [2016-07-13 05:24]:

Pushed to ap/seektell so people can look at how the result looks&feels.

Now in blead as 01f0ef6 (and preceding).

p5pRT · 2016-07-13T19:54:23Z

@cpansprout - Status changed from 'open' to 'pending release'

p5pRT · 2017-05-30T20:14:17Z

From @khwilliamson

Thank you for filing this report. You have helped make Perl better.

With the release today of Perl 5.26.0, this and 210 other issues have been
resolved.

Perl 5.26.0 may be downloaded via:
https://metacpan.org/release/XSAWYERX/perl-5.26.0

If you find that the problem persists, feel free to reopen this ticket.

p5pRT · 2017-05-30T20:14:18Z

@khwilliamson - Status changed from 'pending release' to 'resolved'

p5pRT closed this as completed May 30, 2017

p5pRT added Severity Low distro-All documentation labels Oct 19, 2019

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POD: sysseek #15438

POD: sysseek #15438

Comments

p5pRT commented Jul 12, 2016

p5pRT commented Jul 12, 2016

From niczero@wow.com

p5pRT commented Jul 12, 2016

From @dcollinsn

p5pRT commented Jul 12, 2016

p5pRT commented Jul 12, 2016

From @jkeenan

p5pRT commented Jul 12, 2016

From zefram@fysh.org

p5pRT commented Jul 12, 2016

From @mauke

p5pRT commented Jul 12, 2016

From @dcollinsn

p5pRT commented Jul 13, 2016

From @ap

p5pRT commented Jul 13, 2016

From zefram@fysh.org

p5pRT commented Jul 13, 2016

From @xsawyerx

p5pRT commented Jul 13, 2016

From @ap

p5pRT commented Jul 13, 2016

p5pRT commented May 30, 2017

From @khwilliamson

p5pRT commented May 30, 2017