Warn on some format-related variables when not using formats

p5pRT commented 9 years ago

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

Searchable as RT123751$

p5pRT commented 9 years ago

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 ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please visit http://www.symanteccloud.com ______________________________________________________________________ ```

p5pRT commented 9 years ago

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 commented 9 years ago

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

p5pRT commented 9 years ago

From @epa

Tony Cook via RT \<perlbug-followup \ 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

Perl / perl5