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bogus "used only once" warnings #13309

Open p5pRT opened 11 years ago

p5pRT commented 11 years ago

Migrated from rt.perl.org#119991 (status was 'open')

Searchable as RT119991$

p5pRT commented 11 years ago

From @mauke

Created by @mauke

% perl -we 'sub A​::f; BEGIN { 0 if *{"A​::f"}{CODE} }'

% perl -we 'sub A​::f; BEGIN { 0 if *{"A​::g"}{CODE} }' Name "A​::g" used only once​: possible typo at -e line 1.

% perl -we 'BEGIN { 0 if *{"CORE​::lc"}{CODE} }'

% perl -we 'BEGIN { 0 if *{"CORE​::eval"}{CODE} }' Name "CORE​::eval" used only once​: possible typo at -e line 1.

I don't think this code should trigger any "used only once" warnings. I'm accessing the symbol table via symbolic references; I'm not using any literal variables.

Even so\, why does *{"CORE​::eval"} warn but not *{"CORE​::lc"}?

Perl Info ``` Flags: category=core severity=low This perlbug was built using Perl 5.12.1 - Thu Jun 3 20:09:15 CEST 2010 It is being executed now by Perl 5.18.1 - Tue Aug 13 07:08:47 CEST 2013. Site configuration information for perl 5.18.1: Configured by mauke at Tue Aug 13 07:08:47 CEST 2013. Summary of my perl5 (revision 5 version 18 subversion 1) configuration: Platform: osname=linux, osvers=3.5.7-gentoo, archname=i686-linux uname='linux nora 3.5.7-gentoo #5 preempt sat jan 26 16:46:10 cet 2013 i686 amd athlon(tm) 64 processor 3200+ authenticamd gnulinux ' config_args='' hint=recommended, useposix=true, d_sigaction=define useithreads=undef, usemultiplicity=undef useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef use64bitint=undef, use64bitall=undef, uselongdouble=undef usemymalloc=n, bincompat5005=undef Compiler: cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64', optimize='-O2 -flto', cppflags='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include' ccversion='', gccversion='4.8.1', gccosandvers='' intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12 ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8 alignbytes=4, prototype=define Linker and Libraries: ld='cc', ldflags ='-O2 -flto -fstack-protector -L/usr/local/lib' libpth=/usr/local/lib /lib/../lib /usr/lib/../lib /lib /usr/lib libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc libc=/lib/libc-2.15.so, so=so, useshrplib=false, libperl=libperl.a gnulibc_version='2.15' Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E' cccdlflags='-fPIC', lddlflags='-shared -O2 -flto -L/usr/local/lib -fstack-protector' Locally applied patches: SAVEARGV0 - disable magic open in @INC for perl 5.18.1: /home/mauke/usr/local/lib/perl5/site_perl/5.18.1/i686-linux /home/mauke/usr/local/lib/perl5/site_perl/5.18.1 /home/mauke/usr/local/lib/perl5/5.18.1/i686-linux /home/mauke/usr/local/lib/perl5/5.18.1 . Environment for perl 5.18.1: HOME=/home/mauke LANG=en_US.UTF-8 LANGUAGE (unset) LC_COLLATE=POSIX LD_LIBRARY_PATH=/home/mauke/usr/local/lib LOGDIR (unset) PATH=/home/mauke/usr/perlbrew/bin:/home/mauke/usr/local/bin:/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i686-pc-linux-gnu/gcc-bin/4.6.3:/opt/sun-jdk-1.4.2.13/bin:/opt/sun-jdk-1.4.2.13/jre/bin:/opt/sun-jdk-1.4.2.13/jre/javaws:/opt/dmd/bin:/usr/games/bin PERLBREW_BASHRC_VERSION=0.43 PERLBREW_HOME=/home/mauke/.perlbrew PERLBREW_PATH=/home/mauke/usr/perlbrew/bin PERLBREW_ROOT=/home/mauke/usr/perlbrew PERLBREW_VERSION=0.27 PERL_BADLANG (unset) PERL_UNICODE=SAL SHELL=/bin/bash ```
p5pRT commented 11 years ago

From zefram@fysh.org

l.mai@​web.de wrote​:

Even so\, why does *{"CORE​::eval"} warn but not *{"CORE​::lc"}?

Because \&CORE​::lc is a thing\, but the behaviour of CORE​::eval can't be adequately captured as a sub.

-zefram

p5pRT commented 11 years ago

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

p5pRT commented 11 years ago

From perl@profvince.com

% perl -we 'sub A​::f; BEGIN { 0 if *{"A​::f"}{CODE} }'

% perl -we 'sub A​::f; BEGIN { 0 if *{"A​::g"}{CODE} }' Name "A​::g" used only once​: possible typo at -e line 1.

% perl -we 'BEGIN { 0 if *{"CORE​::lc"}{CODE} }'

% perl -we 'BEGIN { 0 if *{"CORE​::eval"}{CODE} }' Name "CORE​::eval" used only once​: possible typo at -e line 1.

I don't think this code should trigger any "used only once" warnings. I'm accessing the symbol table via symbolic references; I'm not using any literal variables.

perl 5.14.4 also throws the warning. The difference appears with perl 5.16.

Even so\, why does *{"CORE​::eval"} warn but not *{"CORE​::lc"}?

Here's the list of all of them :

$ perl5.18.1 -MB​::Keywords=@​Functions -le'for (@​Functions) { system qq[$^X -we "BEGIN { 0 if *{q\<CORE​::$_>}{CODE} }"] }' Name "CORE​::AUTOLOAD" used only once​: possible typo at -e line 1. Name "CORE​::BEGIN" used only once​: possible typo at -e line 1. Name "CORE​::DESTROY" used only once​: possible typo at -e line 1. Name "CORE​::END" used only once​: possible typo at -e line 1. Name "CORE​::INIT" used only once​: possible typo at -e line 1. Name "CORE​::CHECK" used only once​: possible typo at -e line 1. Name "CORE​::UNITCHECK" used only once​: possible typo at -e line 1. Name "CORE​::dump" used only once​: possible typo at -e line 1. Name "CORE​::eval" used only once​: possible typo at -e line 1. Name "CORE​::format" used only once​: possible typo at -e line 1. Name "CORE​::goto" used only once​: possible typo at -e line 1. Name "CORE​::grep" used only once​: possible typo at -e line 1. Name "CORE​::import" used only once​: possible typo at -e line 1. Name "CORE​::last" used only once​: possible typo at -e line 1. Name "CORE​::local" used only once​: possible typo at -e line 1. Name "CORE​::map" used only once​: possible typo at -e line 1. Name "CORE​::my" used only once​: possible typo at -e line 1. Name "CORE​::next" used only once​: possible typo at -e line 1. Name "CORE​::our" used only once​: possible typo at -e line 1. Name "CORE​::print" used only once​: possible typo at -e line 1. Name "CORE​::printf" used only once​: possible typo at -e line 1. Name "CORE​::redo" used only once​: possible typo at -e line 1. Name "CORE​::require" used only once​: possible typo at -e line 1. Name "CORE​::return" used only once​: possible typo at -e line 1. Name "CORE​::say" used only once​: possible typo at -e line 1. Name "CORE​::sort" used only once​: possible typo at -e line 1. Name "CORE​::state" used only once​: possible typo at -e line 1. Name "CORE​::unimport" used only once​: possible typo at -e line 1. Name "CORE​::use" used only once​: possible typo at -e line 1.

p5pRT commented 6 years ago

From zefram@fysh.org

As discussed\, the warning is not bogus. This ticket should be closed.

-zefram

p5pRT commented 6 years ago

From @iabyn

On Sat\, Dec 16\, 2017 at 04​:00​:51AM +0000\, Zefram wrote​:

As discussed\, the warning is not bogus. This ticket should be closed.

Although \&CORE​::eval returns an undef CV\, as compared to \&CORE​::lc which creates a useful CV\, they both create an entry in the %CORE​:: stash which is a GV with a GvCV slot pointing to a CV.

So its not clear to me why one should warn and the other shouldn't.

-- This is a great day for France!   -- Nixon at Charles De Gaulle's funeral

p5pRT commented 6 years ago

From @cpansprout

On Mon\, 18 Dec 2017 03​:45​:37 -0800\, davem wrote​:

On Sat\, Dec 16\, 2017 at 04​:00​:51AM +0000\, Zefram wrote​:

As discussed\, the warning is not bogus. This ticket should be closed.

Although \&CORE​::eval returns an undef CV\, as compared to \&CORE​::lc which creates a useful CV\, they both create an entry in the %CORE​:: stash which is a GV with a GvCV slot pointing to a CV.

So its not clear to me why one should warn and the other shouldn't.

$ perl5.26.0 -le 'print defined *{"CORE​::lc"}||0; print defined ${"CORE​::eval"}||0;' 1 0

--

Father Chrysostomos