perl592delta - what is new for perl v5.9.2
This document describes differences between the 5.9.1 and the 5.9.2 development releases. See perl590delta and perl591delta for the differences between 5.8.0 and 5.9.1.
The semantics of pack() and unpack() regarding UTF-8-encoded data has been
changed. Processing is now by default character per character instead of
byte per byte on the underlying encoding. Notably, code that used things
like pack("a*", $string)
to see through the encoding of string will now
simply get back the original $string. Packed strings can also get upgraded
during processing when you store upgraded characters. You can get the old
behaviour by using use bytes
.
To be consistent with pack(), the C0
in unpack() templates indicates
that the data is to be processed in character mode, i.e. character by
character; on the contrary, U0
in unpack() indicates UTF-8 mode, where
the packed string is processed in its UTF-8-encoded Unicode form on a byte
by byte basis. This is reversed with regard to perl 5.8.X.
Moreover, C0
and U0
can also be used in pack() templates to specify
respectively character and byte modes.
C0
and U0
in the middle of a pack or unpack format now switch to the
specified encoding mode, honoring parens grouping. Previously, parens were
ignored.
Also, there is a new pack() character format, W
, which is intended to
replace the old C
. C
is kept for unsigned chars coded as bytes in
the strings internal representation. W
represents unsigned (logical)
character values, which can be greater than 255. It is therefore more
robust when dealing with potentially UTF-8-encoded data (as C
will wrap
values outside the range 0..255, and not respect the string encoding).
In practice, that means that pack formats are now encoding-neutral, except
C
.
For consistency, A
in unpack() format now trims all Unicode whitespace
from the end of the string. Before perl 5.9.2, it used to strip only the
classical ASCII space characters.
The internal dump output has been improved, so that non-printable characters
such as newline and backspace are output in \x
notation, rather than
octal.
The -C option can no longer be used on the #!
line. It wasn't
working there anyway.
Perl can now be built to detect attempts to assign pathologically large chunks of memory. Previously such assignments would suffer from integer wrap-around during size calculations causing a misallocation, which would crash perl, and could theoretically be used for "stack smashing" attacks. The wrapping defaults to enabled on platforms where we know it works (most AIX configurations, BSDi, Darwin, DEC OSF/1, FreeBSD, HP-UX, GNU Linux, OpenBSD, Solaris, VMS and most Win32 compilers) and defaults to disabled on other platforms.
The copy of the Unicode Character Database included in Perl 5.9 has been updated to 4.0.1 from 4.0.0.
Paul Szabo has analysed and patched suidperl
to remove existing known
insecurities. Currently there are no known holes in suidperl
, but previous
experience shows that we cannot be confident that these were the last. You may
no longer invoke the set uid perl directly, so to preserve backwards
compatibility with scripts that invoke #!/usr/bin/suidperl the only set uid
binary is now sperl5.9.
n (sperl5.9.2
for this release). suidperl
is installed as a hard link to perl
; both suidperl
and perl
will
invoke sperl5.9.2
automatically the set uid binary, so this change should
be completely transparent.
For new projects the core perl team would strongly recommend that you use
dedicated, single purpose security tools such as sudo
in preference to
suidperl
.
The PERLIO_DEBUG
environment variable has no longer any effect for
setuid scripts and for scripts run with -T.
Moreover, with a thread-enabled perl, using PERLIO_DEBUG
could lead to
an internal buffer overflow. This has been fixed.
In addition to bug fixes, format's features have been enhanced. See
perlform.
Perl's regular expression engine now contains support for matching on the intersection of two Unicode character classes. You can also now refer to user-defined character classes from within other user defined character classes.
There are two new byte-order modifiers, > (big-endian) and <
(little-endian), that can be appended to most pack() and unpack() template
characters and groups to force a certain byte-order for that type or group.
See pack and perlpacktut for details.
A new pack() template character, "."
, returns the number of characters
read so far.
A new variable, ${^RE_DEBUG_FLAGS}, controls what debug flags are in
effect for the regular expression engine when running under use re
"debug"
. See re for details.
A new variable ${^UTF8LOCALE} indicates where a UTF-8 locale was detected by perl at startup.
encoding::warnings
, by Audrey Tang, is a module to emit warnings
whenever an ASCII character string containing high-bit bytes is implicitly
converted into UTF-8.
Module::CoreList
, by Richard Clamp, is a small handy module that tells
you what versions of core modules ship with any versions of Perl 5. It
comes with a command-line frontend, corelist
.
Dual-lived modules have been updated to be kept up-to-date with respect to CPAN.
The dual-lived modules which contain an _
in their version number are
actually ahead of the corresponding CPAN release.
B::Concise
was significantly improved.
There is experimental support for Linux abstract Unix domain sockets.
syslog()
can now use numeric constants for facility names and priorities,
in addition to strings.
Detached threads are now also supported on Windows.
The corelist
utility is now installed with perl (see New modules
above).
h2ph
and h2xs
have been made a bit more robust with regard to
"modern" C code.
Several bugs have been fixed in find2perl
, regarding -exec
and
-eval
. Also the options -path
, -ipath
and -iname
have been
added.
The Perl debugger can now save all debugger commands for sourcing later; notably, it can now emulate stepping backwards, by restarting and rerunning all bar the last command from a saved command history.
It can also display the parent inheritance tree of a given class.
Perl has a new -dt command-line flag, which enables threads support in the debugger.
@a = sort @a
was optimized to do in-place sort. Likewise, reverse
sort ...
is now optimized to sort in reverse, avoiding the generation of
a temporary intermediate list.
Unnecessary assignments are optimised away in
map in scalar context is now optimized.
The regexp engine now implements the trie optimization : it's able to factorize common prefixes and suffixes in regular expressions. A new special variable, ${^RE_TRIE_MAXBUF}, has been added to fine-tune this optimization.
Run-time customization of @INC can be enabled by passing the
-Dusesitecustomize
flag to configure. When enabled, this will make perl
run $sitelibexp/sitecustomize.pl before anything else. This script can
then be set up to add additional entries to @INC.
There is alpha support for relocatable @INC entries.
Perl should build on Interix and on GNU/kFreeBSD.
Most of those bugs were reported in the perl 5.8.x maintenance track. Notably, quite a few utf8 bugs were fixed, and several memory leaks were suppressed. The perl58Xdelta manpages have more details on them.
Development-only bug fixes include :
$Foo::_
was wrongly forced as $main::_
.
A new warning, !=~ should be !~
, is emitted to prevent this misspelling
of the non-matching operator.
The warning Newline in left-justified string has been removed.
The error Too late for "-T" option has been reformulated to be more descriptive.
There is a new compilation error, Illegal declaration of subroutine, for an obscure case of syntax errors.
The diagnostic output of Carp has been changed slightly, to add a space after the comma between arguments. This makes it much easier for tools such as web browsers to wrap it, but might confuse any automatic tools which perform detailed parsing of Carp output.
perl -V
has several improvements, making it more useable from shell
scripts to get the value of configuration variables. See perlrun for
details.
The perl core has been refactored and reorganised in several places. In short, this release will not be binary compatible with any previous perl release.
For threaded builds, ext/threads/shared/t/wait.t has been reported to fail some tests on HP-UX 10.20.
Net::Ping might fail some tests on HP-UX 11.00 with the latest OS upgrades.
t/io/dup.t, t/io/open.t and lib/ExtUtils/t/Constant.t fail some tests on some BSD flavours.
The current plan for perl 5.9.3 is to add CPANPLUS as a core module. More regular expression optimizations are also in the works.
It is planned to release a development version of perl more frequently, i.e. each time something major changes.
If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://bugs.perl.org/ . There may also be information at http://www.perl.org/ , 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.
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.