$^N is ((only) secretly) readonly

p5pRT commented 12 years ago

Migrated from rt.perl.org#112184 (status was 'resolved')

Searchable as RT112184$

p5pRT commented 12 years ago

From tchrist@perl.com

The $^N variable is not assignable\, but attempting to do so raises no exception:

% perl -wle '"foo" =~ /(\w)/; print $^N' f % perl -wle '"foo" =~ /(\w)/; print $^N = 1' f % perl -wle '"foo" =~ /(\w)(?{ $^N = 2})/; print $^N = 1' f

Contrast with $1:

% perl -wle '"foo" =~ /(\w)/; print $1' f % perl -wle '"foo" =~ /(\w)/; print $1 = 1' Modification of a read-only value attempted at -e line 1. Exit 255

--tom

Summary of my perl5 (revision 5 version 14 subversion 0) configuration:
Platform: osname=openbsd\, osvers=4.4\, archname=OpenBSD.i386-openbsd uname='openbsd chthon 4.4 generic#0 i386 ' config_args='-des' 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=y\, bincompat5005=undef Compiler: cc='cc'\, ccflags ='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'\, optimize='-O2'\, cppflags='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include' ccversion=''\, gccversion='3.3.5 (propolice)'\, gccosandvers='openbsd4.4' 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 ='-Wl\,-E -fstack-protector -L/usr/local/lib' libpth=/usr/local/lib /usr/lib libs=-lgdbm -lm -lutil -lc perllibs=-lm -lutil -lc libc=/usr/lib/libc.so.48.0\, so=so\, useshrplib=false\, libperl=libperl.a gnulibc_version='' Dynamic Linking: dlsrc=dl_dlopen.xs\, dlext=so\, d_dlsymun=undef\, ccdlflags=' ' cccdlflags='-DPIC -fPIC '\, lddlflags='-shared -fPIC -L/usr/local/lib -fstack-protector'

Characteristics of this binary (from libperl): Compile-time options: MYMALLOC PERL_DONT_CREATE_GVSV PERL_MALLOC_WRAP PERL_PRESERVE_IVUV USE_LARGE_FILES USE_PERLIO USE_PERL_ATOF Built under openbsd Compiled at Jun 11 2011 11:48:28 %ENV: PERL_UNICODE="SA" @INC: /usr/local/lib/perl5/site_perl/5.14.0/OpenBSD.i386-openbsd /usr/local/lib/perl5/site_perl/5.14.0 /usr/local/lib/perl5/5.14.0/OpenBSD.i386-openbsd /usr/local/lib/perl5/5.14.0 /usr/local/lib/perl5/site_perl/5.12.3 /usr/local/lib/perl5/site_perl/5.11.3 /usr/local/lib/perl5/site_perl/5.10.1 /usr/local/lib/perl5/site_perl/5.10.0 /usr/local/lib/perl5/site_perl/5.8.7 /usr/local/lib/perl5/site_perl/5.8.0 /usr/local/lib/perl5/site_perl/5.6.0 /usr/local/lib/perl5/site_perl/5.005 /usr/local/lib/perl5/site_perl .

p5pRT commented 12 years ago

From @cpansprout

On Sun Apr 01 08:20:52 2012\, tom christiansen wrote:

The $^N variable is not assignable\, but attempting to do so raises no exception:

% perl \-wle '"foo" =~ /\(\\w\)/; print $^N'
f
% perl \-wle '"foo" =~ /\(\\w\)/; print $^N = 1'
f
% perl \-wle '"foo" =~ /\(\\w\)\(?\{ $^N = 2\}\)/; print $^N = 1'
f

Contrast with $1:

% perl \-wle '"foo" =~ /\(\\w\)/; print $1'
f
% perl \-wle '"foo" =~ /\(\\w\)/; print $1 = 1'
Modification of a read\-only value attempted at \-e line 1\.
Exit 255

There is a fix waiting on the sprout/misc-post-5.16 branch.

--

Father Chrysostomos

p5pRT commented 12 years ago

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

p5pRT commented 12 years ago

From @cpansprout

Fixed by d9bad346a1.

p5pRT commented 12 years ago

@cpansprout - Status changed from 'open' to 'resolved'

Perl / perl5