Warn on some format-related variables when not using formats #14478

p5pRT · 2015-02-06T13:47:14Z

Migrated from rt.perl.org#123751 (status was 'open')

Searchable as RT123751$

p5pRT · 2015-02-06T13:47:14Z

From @epa

Created by @epa

Formats are a long-standing feature of perl which many programmers and
programs do not use. This bug is not about getting rid of formats.
However, there are some builtin variables for use with formats which
don't make sense otherwise.

I am particularly thinking of $%, 'the current page number', and
$-, 'the number of lines left'. I can't imagine anyone using these
when not using formats. Their default seems to be zero.

However, they can hide typos in code, e.g. $->[0] for $_->[0].

Please add a warning at run time if these builtin variables are
used but format() has never been called.

It is possible that other format-related variables are set up by some
programs before the first call to format(), so I don't suggest warning
on all of them. But these two in particular seem like nobody would
want to read or set them without calling format() first.

Perl Info


Flags:
    category=core
    severity=low

Site configuration information for perl 5.18.4:

Configured by Red Hat, Inc. at Thu Oct 30 14:55:21 UTC 2014.

Summary of my perl5 (revision 5 version 18 subversion 4) configuration:
   
  Platform:
    osname=linux, osvers=3.16.3-200.fc20.x86_64, archname=x86_64-linux-thread-multi
    uname='linux buildvm-18.phx2.fedoraproject.org 3.16.3-200.fc20.x86_64 #1 smp wed sep 17 22:34:21 utc 2014 x86_64 x86_64 x86_64 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches  -m64 -mtune=generic -Dccdlflags=-Wl,--enable-new-dtags -Dlddlflags=-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches  -m64 -mtune=generic -Wl,-z,relro  -Dshrpdir=/usr/lib64 -DDEBUGGING=-g -Dversion=5.18.4 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dprefix=/usr -Dvendorprefix=/usr -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl5 -Dsitearch=/usr/local/lib64/perl5 -Dprivlib=/usr/share/perl5 -Dvendorlib=/usr/share/perl5/vendor_perl -Darchlib=/usr/lib64/perl5 -Dvendorarch=/usr/lib64/perl5/vendor_perl -Darchname=x86_64-linux-thread-multi -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Duseshrplib -Dusethreads -Duseithreads -Dusedtrace=/usr/bin/dtrace -Duselargefiles -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbinperl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_proto -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dscriptdir=/usr/bin -Dusesitecustomize'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.8.3 20140911 (Red Hat 4.8.3-7)', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =' -fstack-protector'
    libpth=/usr/local/lib64 /lib64 /usr/lib64
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc -lgdbm_compat
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.18'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,--enable-new-dtags'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -Wl,-z,relro '

Locally applied patches:
    Fedora Patch1: Removes date check, Fedora/RHEL specific
    Fedora Patch3: support for libdir64
    Fedora Patch4: use libresolv instead of libbind
    Fedora Patch5: USE_MM_LD_RUN_PATH
    Fedora Patch6: Skip hostname tests, due to builders not being network capable
    Fedora Patch7: Dont run one io test due to random builder failures
    Fedora Patch9: Fix find2perl to translate ? glob properly (RT#113054)
    Fedora Patch10: Update h2ph(1) documentation (RT#117647)
    Fedora Patch11: Update pod2html(1) documentation (RT#117623)
    Fedora Patch12: Disable ornaments on perl5db AutoTrace tests (RT#118817)
    Fedora Patch14: Do not use system Term::ReadLine::Gnu in tests (RT#118821)
    Fedora Patch15: Define SONAME for libperl.so
    Fedora Patch16: Install libperl.so to -Dshrpdir value
    Fedora Patch18: Fix crash with \\&$glob_copy (RT#119051)
    Fedora Patch19: Fix coreamp.t rand test (RT#118237)
    Fedora Patch20: Reap child in case where exception has been thrown (RT#114722)
    Fedora Patch21: Fix using regular expressions containing multiple code blocks (RT#117917)
    Fedora Patch22: Create site paths by cpan for the first time (CPAN RT#99905)
    Fedora Patch200: Link XS modules to libperl.so with EU::CBuilder on Linux
    Fedora Patch201: Link XS modules to libperl.so with EU::MM on Linux


@INC for perl 5.18.4:
    /home/eda/lib/perl5/
    /usr/local/lib64/perl5
    /usr/local/share/perl5
    /usr/lib64/perl5/vendor_perl
    /usr/share/perl5/vendor_perl
    /usr/lib64/perl5
    /usr/share/perl5
    .


Environment for perl 5.18.4:
    HOME=/home/eda
    LANG=en_GB.UTF-8
    LANGUAGE (unset)
    LC_COLLATE=C
    LC_CTYPE=en_GB.UTF-8
    LC_MESSAGES=en_GB.UTF-8
    LC_MONETARY=en_GB.UTF-8
    LC_NUMERIC=en_GB.UTF-8
    LC_TIME=en_GB.UTF-8
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/eda/bin:/home/eda/bin:/usr/local/bin:/usr/bin:/sbin:/usr/sbin:/sbin:/usr/sbin
    PERL5LIB=/home/eda/lib/perl5/
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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p5pRT · 2015-02-09T05:42:49Z

From @tonycoz

On Fri Feb 06 05:47:14 2015, eda@waniasset.com wrote:

Formats are a long-standing feature of perl which many programmers and
programs do not use. This bug is not about getting rid of formats.
However, there are some builtin variables for use with formats which
don't make sense otherwise.

I am particularly thinking of $%, 'the current page number', and
$-, 'the number of lines left'. I can't imagine anyone using these
when not using formats. Their default seems to be zero.

However, they can hide typos in code, e.g. $->[0] for $_->[0].

Please add a warning at run time if these builtin variables are
used but format() has never been called.

It is possible that other format-related variables are set up by some
programs before the first call to format(), so I don't suggest warning
on all of them. But these two in particular seem like nobody would
want to read or set them without calling format() first.

An alternative might be:

https://metacpan.org/pod/Perl::Critic::Policy::Variables::ProhibitEvilVariables

As to warning on those variables, it's possible format is being done somewhere the compiler doesn't see yet, or won't see until runtime.

Tony

p5pRT · 2015-02-09T05:42:49Z

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

p5pRT · 2015-02-09T07:56:49Z

From @epa

Tony Cook via RT <perlbug-followup <at> perl.org> writes:

As to warning on those variables, it's possible format is being done
somewhere the compiler doesn't see yet, or won't see until runtime.

Indeed - which is why this would have to be a run-time warning,
unfortunately.

A global setting 'no formats' would be a way to disable these variables
and others at compile time, but is outside the scope of this bug.

--
Ed Avis <eda@waniasset.com>

p5pRT added Severity Low distro-Linux type-core labels Oct 19, 2019

xenu removed the affects-5.18 label Nov 19, 2021

xenu removed the Severity Low label Dec 29, 2021

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Warn on some format-related variables when not using formats #14478

Warn on some format-related variables when not using formats #14478

p5pRT commented Feb 6, 2015

p5pRT commented Feb 6, 2015

p5pRT commented Feb 9, 2015

p5pRT commented Feb 9, 2015

p5pRT commented Feb 9, 2015

Warn on some format-related variables when not using formats #14478

Warn on some format-related variables when not using formats #14478

Comments

p5pRT commented Feb 6, 2015

p5pRT commented Feb 6, 2015

From @epa

Created by @epa

p5pRT commented Feb 9, 2015

From @tonycoz

p5pRT commented Feb 9, 2015

p5pRT commented Feb 9, 2015

From @epa