PERL570DELTA(1) Perl Programmers Reference Guide PERL570DELTA(1)NAMEperl570delta - what's new for perl v5.7.0
DESCRIPTION
This document describes differences between the 5.6.0
release and the 5.7.0 release.
Security Vulnerability Closed
A potential security vulnerability in the optional suidperl
component of Perl has been identified. suidperl is neither
built nor installed by default. As of September the 2nd,
2000, the only known vulnerable platform is Linux, most
likely all Linux distributions. CERT and various vendors
have been alerted about the vulnerability.
The problem was caused by Perl trying to report a suspected
security exploit attempt using an external program,
/bin/mail. On Linux platforms the /bin/mail program had an
undocumented feature which when combined with suidperl gave
access to a root shell, resulting in a serious compromise
instead of reporting the exploit attempt. If you don't have
/bin/mail, or if you have 'safe setuid scripts', or if suid-
perl is not installed, you are safe.
The exploit attempt reporting feature has been completely
removed from the Perl 5.7.0 release, so that particular vul-
nerability isn't there anymore. However, further security
vulnerabilities are, unfortunately, always possible. The
suidperl code is being reviewed and if deemed too risky to
continue to be supported, it may be completely removed from
future releases. In any case, suidperl should only be used
by security experts who know exactly what they are doing and
why they are using suidperl instead of some other solution
such as sudo ( see http://www.courtesan.com/sudo/ ).
Incompatible Changes
+ Arrays now always interpolate into double-quoted
strings: constructs like "foo@bar" now always assume
@bar is an array, whether or not the compiler has seen
use of @bar.
+ The semantics of bless(REF, REF) were unclear and until
someone proves it to make some sense, it is forbidden.
+ A reference to a reference now stringify as
"REF(0x81485ec)" instead of "SCALAR(0x81485ec)" in order
to be more consistent with the return value of ref().
+ The very dusty examples in the eg/ directory have been
removed. Suggestions for new shiny examples welcome but
the main issue is that the examples need to be docu-
mented, tested and (most importantly) maintained.
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+ The obsolete chat2 library that should never have been
allowed to escape the laboratory has been decommis-
sioned.
+ The unimplemented POSIX regex features [[.cc.]] and
[[=c=]] are still recognised but now cause fatal errors.
The previous behaviour of ignoring them by default and
warning if requested was unacceptable since it, in a
way, falsely promised that the features could be used.
+ The (bogus) escape sequences \8 and \9 now give an
optional warning ("Unrecognized escape passed through").
There is no need to \-escape any "\w" character.
+ lstat(FILEHANDLE) now gives a warning because the opera-
tion makes no sense. In future releases this may become
a fatal error.
+ The long deprecated uppercase aliases for the string
comparison operators (EQ, NE, LT, LE, GE, GT) have now
been removed.
+ The regular expression captured submatches ($1, $2, ...)
are now more consistently unset if the match fails,
instead of leaving false data lying around in them.
+ The tr///C and tr///U features have been removed and
will not return; the interface was a mistake. Sorry
about that. For similar functionality, see pack('U0',
...) and pack('C0', ...).
Core Enhancements
+ "perl -d:Module=arg,arg,arg" now works (previously one
couldn't pass in multiple arguments.)
+ my __PACKAGE__ $obj now works.
+ "no Module;" now works even if there is no "sub unim-
port" in the Module.
+ The numerical comparison operators return "undef" if
either operand is a NaN. Previously the behaviour was
unspecified.
+ "pack('U0a*', ...)" can now be used to force a string to
UTF-8.
+ prototype(\&) is now available.
+ There is now an UNTIE method.
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New Modules
+ File::Temp allows one to create temporary files and
directories in an easy, portable, and secure way.
+ Storable gives persistence to Perl data structures by
allowing the storage and retrieval of Perl data to and
from files in a fast and compact binary format.
Updated And Improved Modules and Pragmata
+ The following independently supported modules have been
updated to newer versions from CPAN: CGI, CPAN, DB_File,
File::Spec, Getopt::Long, the podlators bundle,
Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
+ Bug fixes and minor enhancements have been applied to
B::Deparse, Data::Dumper, IO::Poll, IO::Socket::INET,
Math::BigFloat, Math::Complex, Math::Trig,
Net::protoent, the re pragma, SelfLoader, Sys::SysLog,
Test::Harness, Text::Wrap, UNIVERSAL, and the warnings
pragma.
+ The attributes::reftype() now works on tied arguments.
+ AutoLoader can now be disabled with "no AutoLoader;",
+ The English module can now be used without the infamous
performance hit by saying
use English '-no_performance_hit';
(Assuming, of course, that one doesn't need the trouble-
some variables $`, $&, or $'.) Also, introduced
@LAST_MATCH_START and @LAST_MATCH_END English aliases
for "@-" and "@+".
+ File::Find now has pre- and post-processing callbacks.
It also correctly changes directories when chasing sym-
bolic links. Callbacks (naughtily) exiting with "next;"
instead of "return;" now work.
+ File::Glob::glob() renamed to File::Glob::bsd_glob() to
avoid prototype mismatch with CORE::glob().
+ IPC::Open3 now allows the use of numeric file descrip-
tors.
+ use lib now works identically to @INC. Removing direc-
tories with 'no lib' now works.
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+ %INC now localised in a Safe compartment so that
use/require work.
+ The Shell module now has an OO interface.
Utility Changes
+ The Emacs perl mode (emacs/cperl-mode.el) has been
updated to version 4.31.
+ Perlbug is now much more robust. It also sends the bug
report to perl.org, not perl.com.
+ The perlcc utility has been rewritten and its user
interface (that is, command line) is much more like that
of the UNIX C compiler, cc.
+ The xsubpp utility for extension writers now understands
POD documentation embedded in the *.xs files.
New Documentation
+ perl56delta details the changes between the 5.005
release and the 5.6.0 release.
+ perldebtut is a Perl debugging tutorial.
+ perlebcdic contains considerations for running Perl on
EBCDIC platforms. Note that unfortunately EBCDIC plat-
forms that used to supported back in Perl 5.005 are
still unsupported by Perl 5.7.0; the plan, however, is
to bring them back to the fold.
+ perlnewmod tells about writing and submitting a new
module.
+ perlposix-bc explains using Perl on the POSIX-BC plat-
form (an EBCDIC mainframe platform).
+ perlretut is a regular expression tutorial.
+ perlrequick is a regular expressions quick-start guide.
Yes, much quicker than perlretut.
+ perlutil explains the command line utilities packaged
with the Perl distribution.
Performance Enhancements
+ map() that changes the size of the list should now work
faster.
+ sort() has been changed to use mergesort internally as
opposed to the earlier quicksort. For very small lists
this may result in slightly slower sorting times, but in
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general the speedup should be at least 20%. Additional
bonuses are that the worst case behaviour of sort() is
now better (in computer science terms it now runs in
time O(N log N), as opposed to quicksort's Theta(N**2)
worst-case run time behaviour), and that sort() is now
stable (meaning that elements with identical keys will
stay ordered as they were before the sort).
Installation and Configuration Improvements
Generic Improvements
+ INSTALL now explains how you can configure Perl to use
64-bit integers even on non-64-bit platforms.
+ Policy.sh policy change: if you are reusing a Policy.sh
file (see INSTALL) and you use Configure
-Dprefix=/foo/bar and in the old Policy $prefix eq
$siteprefix and $prefix eq $vendorprefix, all of them
will now be changed to the new prefix, /foo/bar. (Pre-
viously only $prefix changed.) If you do not like this
new behaviour, specify prefix, siteprefix, and ven-
dorprefix explicitly.
+ A new optional location for Perl libraries, otherlib-
dirs, is available. It can be used for example for ven-
dor add-ons without disturbing Perl's own library direc-
tories.
+ In many platforms the vendor-supplied 'cc' is too
stripped-down to build Perl (basically, 'cc' doesn't do
ANSI C). If this seems to be the case and 'cc' does not
seem to be the GNU C compiler 'gcc', an automatic
attempt is made to find and use 'gcc' instead.
+ gcc needs to closely track the operating system release
to avoid build problems. If Configure finds that gcc was
built for a different operating system release than is
running, it now gives a clearly visible warning that
there may be trouble ahead.
+ If binary compatibility with the 5.005 release is not
wanted, Configure no longer suggests including the 5.005
modules in @INC.
+ Configure "-S" can now run non-interactively.
+ configure.gnu now works with options with whitespace in
them.
+ installperl now outputs everything to STDERR.
+ $Config{byteorder} is now computed dynamically (this is
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more robust with "fat binaries" where an executable
image contains binaries for more than one binary plat-
form.)
Selected Bug Fixes
+ Several debugger fixes: exit code now reflects the
script exit code, condition "0" now treated correctly,
the "d" command now checks line number, the $. no longer
gets corrupted, all debugger output now goes correctly
to the socket if RemotePort is set.
+ *foo{FORMAT} now works.
+ Lexical warnings now propagating correctly between
scopes.
+ Line renumbering with eval and "#line" now works.
+ Fixed numerous memory leaks, especially in eval "".
+ Modulus of unsigned numbers now works (4063328477 %
65535 used to return 27406, instead of 27047).
+ Some "not a number" warnings introduced in 5.6.0 elim-
inated to be more compatible with 5.005. Infinity is
now recognised as a number.
+ our() variables will not cause "will not stay shared"
warnings.
+ pack "Z" now correctly terminates the string with "\0".
+ Fix password routines which in some shadow password
platforms (e.g. HP-UX) caused getpwent() to return every
other entry.
+ printf() no longer resets the numeric locale to "C".
+ "q(a\\b)" now parses correctly as 'a\\b'.
+ Printing quads (64-bit integers) with printf/sprintf now
works without the q L ll prefixes (assuming you are on a
quad-capable platform).
+ Regular expressions on references and overloaded scalars
now work.
+ scalar() now forces scalar context even when used in
void context.
+ sort() arguments are now compiled in the right wantarray
context (they were accidentally using the context of the
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+ Changed the POSIX character class "[[:space:]]" to
include the (very rare) vertical tab character. Added a
new POSIX-ish character class "[[:blank:]]" which stands
for horizontal whitespace (currently, the space and the
tab).
+ $AUTOLOAD, sort(), lock(), and spawning subprocesses in
multiple threads simultaneously are now thread-safe.
+ Allow read-only string on left hand side of non-
modifying tr///.
+ Several Unicode fixes (but still not perfect).
+ BOMs (byte order marks) in the beginning of Perl
files (scripts, modules) should now be tran-
sparently skipped. UTF-16 (UCS-2) encoded Perl
files should now be read correctly.
+ The character tables have been updated to
Unicode 3.0.1.
+ chr() for values greater than 127 now create
utf8 when under use utf8.
+ Comparing with utf8 data does not magically
upgrade non-utf8 data into utf8.
+ "IsAlnum", "IsAlpha", and "IsWord" now match
titlecase.
+ Concatenation with the "." operator or via vari-
able interpolation, "eq", "substr", "reverse",
"quotemeta", the "x" operator, substitution with
"s///", single-quoted UTF-8, should now work--in
theory.
+ The "tr///" operator now works slightly better
but is still rather broken. Note that the
"tr///CU" functionality has been removed (but
see pack('U0', ...)).
+ vec() now refuses to deal with characters >255.
+ Zero entries were missing from the Unicode
classes like "IsDigit".
+ UNIVERSAL::isa no longer caches methods incorrectly.
(This broke the Tk extension with 5.6.0.)
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Platform Specific Changes and Fixes
+ BSDI 4.*
Perl now works on post-4.0 BSD/OSes.
+ All BSDs
Setting $0 now works (as much as possible; see perlvar
for details).
+ Cygwin
Numerous updates; currently synchronised with Cygwin
1.1.4.
+ EPOC
EPOC update after Perl 5.6.0. See README.epoc.
+ FreeBSD 3.*
Perl now works on post-3.0 FreeBSDs.
+ HP-UX
README.hpux updated; "Configure -Duse64bitall" now
almost works.
+ IRIX
Numerous compilation flag and hint enhancements;
accidental mixing of 32-bit and 64-bit libraries (a
doomed attempt) made much harder.
+ Linux
Long doubles should now work (see INSTALL).
+ Mac OS Classic
Compilation of the standard Perl distribution in Mac OS
Classic should now work if you have the Metrowerks
development environment and the missing Mac-specific
toolkit bits. Contact the macperl mailing list for
details.
+ MPE/iX
MPE/iX update after Perl 5.6.0. See README.mpeix.
+ NetBSD/sparc
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Perl now works on NetBSD/sparc.
+ OS/2
Now works with usethreads (see INSTALL).
+ Solaris
64-bitness using the Sun Workshop compiler now works.
+ Tru64 (aka Digital UNIX, aka DEC OSF/1)
The operating system version letter now recorded in
$Config{osvers}. Allow compiling with gcc (previously
explicitly forbidden). Compiling with gcc still not
recommended because buggy code results, even with gcc
2.95.2.
+ Unicos
Fixed various alignment problems that lead into core
dumps either during build or later; no longer dies on
math errors at runtime; now using full quad integers (64
bits), previously was using only 46 bit integers for
speed.
+ VMS
chdir() now works better despite a CRT bug; now works
with MULTIPLICITY (see INSTALL); now works with Perl's
malloc.
+ Windows
+ accept() no longer leaks memory.
+ Better chdir() return value for a non-existent
directory.
+ New %ENV entries now propagate to subprocesses.
+ $ENV{LIB} now used to search for libs under
Visual C.
+ A failed (pseudo)fork now returns undef and sets
errno to EAGAIN.
+ Allow REG_EXPAND_SZ keys in the registry.
+ Can now send() from all threads, not just the
first one.
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+ Fake signal handling reenabled, bugs and all.
+ Less stack reserved per thread so that more
threads can run concurrently. (Still 16M per
thread.)
+ "File::Spec->tmpdir()" now prefers C:/temp over
/tmp (works better when perl is running as ser-
vice).
+ Better UNC path handling under ithreads.
+ wait() and waitpid() now work much better.
+ winsock handle leak fixed.
New or Changed Diagnostics
All regular expression compilation error messages are now
hopefully easier to understand both because the error mes-
sage now comes before the failed regex and because the point
of failure is now clearly marked.
The various "opened only for", "on closed", "never opened"
warnings drop the "main::" prefix for filehandles in the
"main" package, for example "STDIN" instead of
<main::STDIN>.
The "Unrecognized escape" warning has been extended to
include "\8", "\9", and "\_". There is no need to escape
any of the "\w" characters.
Changed Internals
+ perlapi.pod (a companion to perlguts) now attempts to
document the internal API.
+ You can now build a really minimal perl called micro-
perl. Building microperl does not require even running
Configure; "make -f Makefile.micro" should be enough.
Beware: microperl makes many assumptions, some of which
may be too bold; the resulting executable may crash or
otherwise misbehave in wondrous ways. For careful hack-
ers only.
+ Added rsignal(), whichsig(), do_join() to the publicised
API.
+ Made possible to propagate customised exceptions via
croak()ing.
+ Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(),
and utf8_to_bytes().
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+ Now xsubs can have attributes just like subs.
Known Problems
Unicode Support Still Far From Perfect
We're working on it. Stay tuned.
EBCDIC Still A Lost Platform
The plan is to bring them back.
Building Extensions Can Fail Because Of Largefiles
Certain extensions like mod_perl and BSD::Resource are known
to have issues with `largefiles', a change brought by Perl
5.6.0 in which file offsets default to 64 bits wide, where
supported. Modules may fail to compile at all or compile
and work incorrectly. Currently there is no good solution
for the problem, but Configure now provides appropriate
non-largefile ccflags, ldflags, libswanted, and libs in the
%Config hash (e.g., $Config{ccflags_nolargefiles}) so the
extensions that are having problems can try configuring
themselves without the largefileness. This is admittedly
not a clean solution, and the solution may not even work at
all. One potential failure is whether one can (or, if one
can, whether it's a good idea) link together at all binaries
with different ideas about file offsets, all this is
platform-dependent.
ftmp-security tests warn 'system possibly insecure'
Don't panic. Read INSTALL 'make test' section instead.
Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
If perl is configured with -Duse64bitall, the successful
result of the subtest 10 of lib/posix may arrive before the
successful result of the subtest 9, which confuses the test
harness so much that it thinks the subtest 9 failed.
Long Doubles Still Don't Work In Solaris
The experimental long double support is still very much so
in Solaris. (Other platforms like Linux and Tru64 are begin-
ning to solidify in this area.)
Linux With Sfio Fails op/misc Test 48
No known fix.
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Storable tests fail in some platforms
If any Storable tests fail the use of Storable is not advis-
able.
+ Many Storable tests fail on AIX configured with 64 bit
integers.
So far unidentified problems break Storable in AIX if
Perl is configured to use 64 bit integers. AIX in
32-bit mode works and other 64-bit platforms work with
Storable.
+ DOS DJGPP may hang when testing Storable.
+ st-06compat fails in UNICOS and UNICOS/mk.
This means that you cannot read old (pre-Storable-0.7)
Storable images made in other platforms.
+ st-store.t and st-retrieve may fail with Compaq C 6.2 on
OpenVMS Alpha 7.2.
Threads Are Still Experimental
Multithreading is still an experimental feature. Some plat-
forms emit the following message for lib/thr5005
#
# This is a KNOWN FAILURE, and one of the reasons why threading
# is still an experimental feature. It is here to stop people
# from deploying threads in production. ;-)
#
and another known thread-related warning is
pragma/overload......Unbalanced saves: 3 more saves than restores
panic: magic_mutexfree during global destruction.
ok
lib/selfloader.......Unbalanced saves: 3 more saves than restores
panic: magic_mutexfree during global destruction.
ok
lib/st-dclone........Unbalanced saves: 3 more saves than restores
panic: magic_mutexfree during global destruction.
ok
The Compiler Suite Is Still Experimental
The compiler suite is slowly getting better but is nowhere
near working order yet. The backend part that has seen
perhaps the most progress is the bytecode compiler.
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PERL570DELTA(1) Perl Programmers Reference Guide PERL570DELTA(1)Reporting Bugs
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc news-
group and the perl bug database at http://bugs.perl.org/
There may also be information at http://www.perl.com/perl/ ,
the Perl Home Page.
If you believe you have an unreported bug, please run the
perlbug program included with your release. Be sure to trim
your bug down to a tiny but sufficient test case. Your bug
report, along with the output of "perl -V", will be sent off
to perlbug@perl.org to be analysed by the Perl porting team.
SEE ALSO
The Changes file for exhaustive details on what changed.
The INSTALL file for how to build Perl.
The README file for general stuff.
The Artistic and Copying files for copyright information.
HISTORY
Written by Jarkko Hietaniemi <jhi@iki.fi>, with many contri-
butions from The Perl Porters and Perl Users submitting
feedback and patches.
Send omissions or corrections to <perlbug@perl.org>.
perl v5.8.8 2006-06-30 13
