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[perl #63368] Ternary operator misparsed as regexp

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From:
Ed Avis
Date:
February 20, 2009 09:36
Subject:
[perl #63368] Ternary operator misparsed as regexp
Message ID:
rt-3.6.HEAD-21965-1235135838-1269.63368-75-0@perl.org
# New Ticket Created by  "Ed Avis" 
# Please include the string:  [perl #63368]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=63368 >


This is a bug report for perl from eda@waniasset.com,
generated with the help of perlbug 1.36 running under perl 5.10.0.


-----------------------------------------------------------------
[Please enter your report here]

This test program:

    sub a {}
    my @x = a ? 0 : 0;

produces the syntax error

    Search pattern not terminated at test line 2.

I had expected it to be syntactically correct (the subroutine a is
defined before it is used, so it's okay to call it without parens).

I understand that sometimes the parser gets confused between the ? :
ternary operator and the ?? one-time regexp operator.  But in these
cases there is normally a hint in the error message that it might have
made the wrong choice.  If it's not possible to fix the misparsing,
then a second best fix would be to change the error message to
something like

    Search pattern not terminated, or ternary operator misparsed
    as ?? regular expression at test line 2.

Such a message would appear only when the delimiter of the regexp is
the ? character and there has been a syntax error at or following it.

In general, the ambiguity between ? : and ?? seems to cause trouble,
and you may want to fix it by deprecating the ?? regexp match operator
or perhaps introducing a new ?? :: syntax for the ternary operator as
used in perl 6.

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
This perlbug was built using Perl 5.10.0 in the Fedora build system.
It is being executed now by Perl 5.10.0 - Mon Feb 16 13:34:09 EST 2009.

Site configuration information for perl 5.10.0:

Configured by Red Hat, Inc. at Mon Feb 16 13:34:09 EST 2009.

Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.6.18-92.1.18.el5, archname=i386-linux-thread-multi
    uname='linux x86-2.fedora.phx.redhat.com 2.6.18-92.1.18.el5 #1 smp wed nov 5 09:00:19 est 2008 i686 i686 i386 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -DPERL_USE_SAFE_PUTENV -Dversion=5.10.0 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dprefix=/usr -Dvendorprefix=/usr -Dsiteprefix=/usr/local -Dprivlib=/usr/lib/perl5/5.10.0 -Dsitelib=/usr/local/lib/perl5/site_perl/5.10.0 -Dvendorlib=/usr/lib/perl5/vendor_perl/5.10.0 -Darchlib=/usr/lib/perl5/5.10.0/i386-linux-thread-multi -Dsitearch=/usr/local/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi -Dvendorarch=/usr/lib/perl5/vendor_perl/5.10.0/i386-linux-thread-multi -Dinc_version_list=none -Darchname=i386-linux-thread-multi -Duseshrplib -Dusethreads -Duseithreads -Duselargefiles -Dd_dosuid -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 -Dotherlibdirs=/usr/local/lib/perl5/site_perl:/usr/lib/perl5/site_perl'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBUGGING -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -DPERL_USE_SAFE_PUTENV',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBUGGING -fno-strict-aliasing -pipe -I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='4.3.2 20081105 (Red Hat 4.3.2-7)', 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='gcc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.9.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.9'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/usr/lib/perl5/5.10.0/i386-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -DPERL_USE_SAFE_PUTENV -L/usr/local/lib'

Locally applied patches:
    

---
@INC for perl 5.10.0:
    /home/eda/lib/perl5/5.10.0/i386-linux-thread-multi
    /home/eda/lib/perl5/5.10.0
    /home/eda/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi
    /home/eda/lib/perl5/site_perl/5.10.0
    /usr/lib/perl5/5.10.0/i386-linux-thread-multi
    /usr/lib/perl5/5.10.0
    /usr/local/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi
    /usr/local/lib/perl5/site_perl/5.10.0
    /usr/lib/perl5/vendor_perl/5.10.0/i386-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.10.0
    /usr/lib/perl5/vendor_perl
    /usr/local/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi
    /usr/local/lib/perl5/site_perl/5.10.0
    /usr/local/lib/perl5/site_perl
    /usr/lib/perl5/site_perl/5.10.0
    /usr/lib/perl5/site_perl
    .

---
Environment for perl 5.10.0:
    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/lib/qt-3.3/bin:/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/home/eda/bin
    PERL5LIB=/home/eda/lib/perl5/5.10.0:/home/eda/lib/perl5/site_perl/5.10.0
    PERL_BADLANG (unset)
    SHELL=/bin/bash

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