[perl #117261] Assigning number to %SIG should fail

# New Ticket Created by  "Ed Avis" 
# Please include the string:  [perl #117261]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=117261 >


This is a bug report for perl from eda@waniasset.com,
generated with the help of perlbug 1.39 running under perl 5.16.2.


-----------------------------------------------------------------
[Please describe your issue here]

The %SIG hash lets you store a code ref, the magic keywords 'DEFAULT' or 'IGNORE', or another string.
In the third case it is taken as the name of a subroutine to call.

However, you can store strings such as '1' which are not legal subroutine names
(except in code that goes to special lengths to mess with the symbol table).
It looks like the current behaviour is for these to be silently ignored, but
it would be better for perl to die or at least warn when this happens.  For example

    $SIG{__WARN__} = 1;   # should fail somehow

This would be useful because it would catch the mistake of putting code instead of an anonymous sub:

    $SIG{__WARN__} = say 'something went wrong';

With this proposed change, the return value of say() being 0 or 1 would not be
a legal subroutine name, so perl would not allow it to be stored in $SIG{__WARN__}.

I might also suggest that 'use strict' should disable storing the names of subroutines
in the hash, in the same way it disables treating a subroutine name as a code ref.
But that might break existing code.

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.16.2:

Configured by Red Hat, Inc. at Mon Feb 18 16:52:57 UTC 2013.

Summary of my perl5 (revision 5 version 16 subversion 2) configuration:
   
  Platform:
    osname=linux, osvers=2.6.32-279.19.1.el6.x86_64, archname=x86_64-linux-thread-multi
    uname='linux buildvm-11.phx2.fedoraproject.org 2.6.32-279.19.1.el6.x86_64 #1 smp sat nov 24 14:35:28 est 2012 x86_64 x86_64 x86_64 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4  -m64 -mtune=generic -Dccdlflags=-Wl,--enable-new-dtags -Dlddlflags=-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4  -m64 -mtune=generic -Wl,-z,relro  -DDEBUGGING=-g -Dversion=5.16.2 -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 -Dinstallusrbinp
 erl=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 --param=ssp-buffer-size=4 -m64 -mtune=generic',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.7.2 20121109 (Red Hat 4.7.2-8)', 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='2.16'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,--enable-new-dtags -Wl,-rpath,/usr/lib64/perl5/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Wl,-z,relro '

Locally applied patches:
    

---
@INC for perl 5.16.2:
    /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 5.16.2:
    HOME=/home/tradingsystems
    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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• [perl #117261] Assigning number to %SIG should fail by Ed Avis
• Re: [perl #117261] Assigning number to %SIG should fail by Zefram
• RE: [perl #117261] Assigning number to %SIG should fail by Ed Avis
• Re: [perl #117261] Assigning number to %SIG should fail by Zefram
• RE: [perl #117261] Assigning number to %SIG should fail by Ed Avis