PERL5280DELTA(1pm) Perl Programmers Reference Guide PERL5280DELTA(1pm)
NAME
perl5280delta - what is new for perl v5.28.0
DESCRIPTION
This document describes differences between the 5.26.0 release and the
5.28.0 release.
If you are upgrading from an earlier release such as 5.24.0, first read
perl5260delta, which describes differences between 5.24.0 and 5.26.0.
Core Enhancements
Unicode 10.0 is supported
A list of changes is at
<http://www.unicode.org/versions/Unicode10.0.0>.
"delete" on key/value hash slices
"delete" can now be used on key/value hash slices, returning the keys
along with the deleted values. [GH #15982]
<https://github.com/Perl/perl5/issues/15982>
Experimentally, there are now alphabetic synonyms for some regular
expression assertions
If you find it difficult to remember how to write certain of the
pattern assertions, there are now alphabetic synonyms.
CURRENT NEW SYNONYMS
------ ------------
(?=...) (*pla:...) or (*positive_lookahead:...)
(?!...) (*nla:...) or (*negative_lookahead:...)
(?<=...) (*plb:...) or (*positive_lookbehind:...)
(?<!...) (*nlb:...) or (*negative_lookbehind:...)
(?>...) (*atomic:...)
These are considered experimental, so using any of these will raise
(unless turned off) a warning in the "experimental::alpha_assertions"
category.
Mixed Unicode scripts are now detectable
A mixture of scripts, such as Cyrillic and Latin, in a string is often
the sign of a spoofing attack. A new regular expression construct now
allows for easy detection of these. For example, you can say
qr/(*script_run: \d+ \b )/x
And the digits matched will all be from the same set of 10. You won't
get a look-alike digit from a different script that has a different
value than what it appears to be.
Or:
qr/(*sr: \b \w+ \b )/x
makes sure that all the characters come from the same script.
You can also combine script runs with "(?>...)" (or "*atomic:...)").
Instead of writing:
(*sr:(?<...))
you can now run:
(*asr:...)
# or
(*atomic_script_run:...)
This is considered experimental, so using it will raise (unless turned
off) a warning in the "experimental::script_run" category.
See "Script Runs" in perlre.
In-place editing with "perl -i" is now safer
Previously in-place editing ("perl -i") would delete or rename the
input file as soon as you started working on a new file.
Without backups this would result in loss of data if there was an
error, such as a full disk, when writing to the output file.
This has changed so that the input file isn't replaced until the output
file has been completely written and successfully closed.
This works by creating a work file in the same directory, which is
renamed over the input file once the output file is complete.
Incompatibilities:
o Since this renaming needs to only happen once, if you create a
thread or child process, that renaming will only happen in the
original thread or process.
o If you change directories while processing a file, and your
operating system doesn't provide the "unlinkat()", "renameat()" and
"fchmodat()" functions, the final rename step may fail.
[GH #15216] <https://github.com/Perl/perl5/issues/15216>
Initialisation of aggregate state variables
A persistent lexical array or hash variable can now be initialized, by
an expression such as "state @a = qw(x y z)". Initialization of a list
of persistent lexical variables is still not possible.
Full-size inode numbers
On platforms where inode numbers are of a type larger than perl's
native integer numerical types, stat will preserve the full content of
large inode numbers by returning them in the form of strings of decimal
digits. Exact comparison of inode numbers can thus be achieved by
comparing with "eq" rather than "==". Comparison with "==", and other
numerical operations (which are usually meaningless on inode numbers),
work as well as they did before, which is to say they fall back to
floating point, and ultimately operate on a fairly useless rounded
inode number if the real inode number is too big for the floating point
format.
The "sprintf" %j format size modifier is now available with pre-C99
compilers
The actual size used depends on the platform, so remains unportable.
Close-on-exec flag set atomically
When opening a file descriptor, perl now generally opens it with its
close-on-exec flag already set, on platforms that support doing so.
This improves thread safety, because it means that an "exec" initiated
by one thread can no longer cause a file descriptor in the process of
being opened by another thread to be accidentally passed to the
executed program.
Additionally, perl now sets the close-on-exec flag more reliably,
whether it does so atomically or not. Most file descriptors were
getting the flag set, but some were being missed.
String- and number-specific bitwise ops are no longer experimental
The new string-specific ("&. |. ^. ~.") and number-specific ("& | ^ ~")
bitwise operators introduced in Perl 5.22 that are available within the
scope of "use feature 'bitwise'" are no longer experimental. Because
the number-specific ops are spelled the same way as the existing
operators that choose their behaviour based on their operands, these
operators must still be enabled via the "bitwise" feature, in either of
these two ways:
use feature "bitwise";
use v5.28; # "bitwise" now included
They are also now enabled by the -E command-line switch.
The "bitwise" feature no longer emits a warning. Existing code that
disables the "experimental::bitwise" warning category that the feature
previously used will continue to work.
One caveat that module authors ought to be aware of is that the numeric
operators now pass a fifth TRUE argument to overload methods. Any
methods that check the number of operands may croak if they do not
expect so many. XS authors in particular should be aware that this:
SV *
bitop_handler (lobj, robj, swap)
may need to be changed to this:
SV *
bitop_handler (lobj, robj, swap, ...)
Locales are now thread-safe on systems that support them
These systems include Windows starting with Visual Studio 2005, and in
POSIX 2008 systems.
The implication is that you are now free to use locales and change them
in a threaded environment. Your changes affect only your thread. See
"Multi-threaded operation" in perllocale
New read-only predefined variable "${^SAFE_LOCALES}"
This variable is 1 if the Perl interpreter is operating in an
environment where it is safe to use and change locales (see
perllocale.) This variable is true when the perl is unthreaded, or
compiled in a platform that supports thread-safe locale operation (see
previous item).
Security
[CVE-2017-12837] Heap buffer overflow in regular expression compiler
Compiling certain regular expression patterns with the case-insensitive
modifier could cause a heap buffer overflow and crash perl. This has
now been fixed. [GH #16021]
<https://github.com/Perl/perl5/issues/16021>
[CVE-2017-12883] Buffer over-read in regular expression parser
For certain types of syntax error in a regular expression pattern, the
error message could either contain the contents of a random, possibly
large, chunk of memory, or could crash perl. This has now been fixed.
[GH #16025] <https://github.com/Perl/perl5/issues/16025>
[CVE-2017-12814] $ENV{$key} stack buffer overflow on Windows
A possible stack buffer overflow in the %ENV code on Windows has been
fixed by removing the buffer completely since it was superfluous
anyway. [GH #16051] <https://github.com/Perl/perl5/issues/16051>
Default Hash Function Change
Perl 5.28.0 retires various older hash functions which are not viewed
as sufficiently secure for use in Perl. We now support four general
purpose hash functions, Siphash (2-4 and 1-3 variants), and Zaphod32,
and StadtX hash. In addition we support SBOX32 (a form of tabular
hashing) for hashing short strings, in conjunction with any of the
other hash functions provided.
By default Perl is configured to support SBOX hashing of strings up to
24 characters, in conjunction with StadtX hashing on 64 bit builds, and
Zaphod32 hashing for 32 bit builds.
You may control these settings with the following options to Configure:
-DPERL_HASH_FUNC_SIPHASH
-DPERL_HASH_FUNC_SIPHASH13
-DPERL_HASH_FUNC_STADTX
-DPERL_HASH_FUNC_ZAPHOD32
To disable SBOX hashing you can use
-DPERL_HASH_USE_SBOX32_ALSO=0
And to set the maximum length to use SBOX32 hashing on with:
-DSBOX32_MAX_LEN=16
The maximum length allowed is 256. There probably isn't much point in
setting it higher than the default.
Incompatible Changes
Subroutine attribute and signature order
The experimental subroutine signatures feature has been changed so that
subroutine attributes must now come before the signature rather than
after. This is because attributes like ":lvalue" can affect the
compilation of code within the signature, for example:
sub f :lvalue ($a = do { $x = "abc"; return substr($x,0,1)}) { ...}
Note that this the second time they have been flipped:
sub f :lvalue ($a, $b) { ... }; # 5.20; 5.28 onwards
sub f ($a, $b) :lvalue { ... }; # 5.22 - 5.26
Comma-less variable lists in formats are no longer allowed
Omitting the commas between variables passed to formats is no longer
allowed. This has been deprecated since Perl 5.000.
The ":locked" and ":unique" attributes have been removed
These have been no-ops and deprecated since Perl 5.12 and 5.10,
respectively.
"\N{}" with nothing between the braces is now illegal
This has been deprecated since Perl 5.24.
Opening the same symbol as both a file and directory handle is no longer
allowed
Using "open()" and "opendir()" to associate both a filehandle and a
dirhandle to the same symbol (glob or scalar) has been deprecated since
Perl 5.10.
Use of bare "<<" to mean "<<""" is no longer allowed
Use of a bare terminator has been deprecated since Perl 5.000.
Setting $/ to a reference to a non-positive integer no longer allowed
This used to work like setting it to "undef", but has been deprecated
since Perl 5.20.
Unicode code points with values exceeding "IV_MAX" are now fatal
This was deprecated since Perl 5.24.
The "B::OP::terse" method has been removed
Use "B::Concise::b_terse" instead.
Use of inherited AUTOLOAD for non-methods is no longer allowed
This was deprecated in Perl 5.004.
Use of strings with code points over 0xFF is not allowed for bitwise string
operators
Code points over 0xFF do not make sense for bitwise operators and such
an operation will now croak, except for a few remaining cases. See
perldeprecation.
This was deprecated in Perl 5.24.
Setting "${^ENCODING}" to a defined value is now illegal
This has been deprecated since Perl 5.22 and a no-op since Perl 5.26.
Backslash no longer escapes colon in PATH for the "-S" switch
Previously the "-S" switch incorrectly treated backslash ("\") as an
escape for colon when traversing the "PATH" environment variable. [GH
#15584] <https://github.com/Perl/perl5/issues/15584>
the -DH (DEBUG_H) misfeature has been removed
On a perl built with debugging support, the "H" flag to the "-D"
debugging option has been removed. This was supposed to dump hash
values, but has been broken for many years.
Yada-yada is now strictly a statement
By the time of its initial stable release in Perl 5.12, the "..."
(yada-yada) operator was explicitly intended to serve as a statement,
not an expression. However, the original implementation was confused
on this point, leading to inconsistent parsing. The operator was
accidentally accepted in a few situations where it did not serve as a
complete statement, such as
... . "foo";
... if $a < $b;
The parsing has now been made consistent, permitting yada-yada only as
a statement. Affected code can use "do{...}" to put a yada-yada into
an arbitrary expression context.
Sort algorithm can no longer be specified
Since Perl 5.8, the sort pragma has had subpragmata "_mergesort",
"_quicksort", and "_qsort" that can be used to specify which algorithm
perl should use to implement the sort builtin. This was always
considered a dubious feature that might not last, hence the underscore
spellings, and they were documented as not being portable beyond Perl
5.8. These subpragmata have now been deleted, and any attempt to use
them is an error. The sort pragma otherwise remains, and the
algorithm-neutral "stable" subpragma can be used to control sorting
behaviour. [GH #13234] <https://github.com/Perl/perl5/issues/13234>
Over-radix digits in floating point literals
Octal and binary floating point literals used to permit any hexadecimal
digit to appear after the radix point. The digits are now restricted
to those appropriate for the radix, as digits before the radix point
always were.
Return type of "unpackstring()"
The return types of the C API functions "unpackstring()" and
"unpack_str()" have changed from "I32" to "SSize_t", in order to
accommodate datasets of more than two billion items.
Deprecations
Use of "vec" on strings with code points above 0xFF is deprecated
Such strings are represented internally in UTF-8, and "vec" is a bit-
oriented operation that will likely give unexpected results on those
strings.
Some uses of unescaped "{" in regexes are no longer fatal
Perl 5.26.0 fatalized some uses of an unescaped left brace, but an
exception was made at the last minute, specifically crafted to be a
minimal change to allow GNU Autoconf to work. That tool is heavily
depended upon, and continues to use the deprecated usage. Its use of
an unescaped left brace is one where we have no intention of
repurposing "{" to be something other than itself.
That exception is now generalized to include various other such cases
where the "{" will not be repurposed.
Note that these uses continue to raise a deprecation message.
Use of unescaped "{" immediately after a "(" in regular expression patterns
is deprecated
Using unescaped left braces is officially deprecated everywhere, but it
is not enforced in contexts where their use does not interfere with
expected extensions to the language. A deprecation is added in this
release when the brace appears immediately after an opening
parenthesis. Before this, even if the brace was part of a legal
quantifier, it was not interpreted as such, but as the literal
characters, unlike other quantifiers that follow a "(" which are
considered errors. Now, their use will raise a deprecation message,
unless turned off.
Assignment to $[ will be fatal in Perl 5.30
Assigning a non-zero value to $[ has been deprecated since Perl 5.12,
but was never given a deadline for removal. This has now been
scheduled for Perl 5.30.
hostname() won't accept arguments in Perl 5.32
Passing arguments to "Sys::Hostname::hostname()" was already
deprecated, but didn't have a removal date. This has now been
scheduled for Perl 5.32. [GH #14662]
<https://github.com/Perl/perl5/issues/14662>
Module removals
The following modules will be removed from the core distribution in a
future release, and will at that time need to be installed from CPAN.
Distributions on CPAN which require these modules will need to list
them as prerequisites.
The core versions of these modules will now issue "deprecated"-category
warnings to alert you to this fact. To silence these deprecation
warnings, install the modules in question from CPAN.
Note that these are (with rare exceptions) fine modules that you are
encouraged to continue to use. Their disinclusion from core primarily
hinges on their necessity to bootstrapping a fully functional, CPAN-
capable Perl installation, not usually on concerns over their design.
B::Debug
Locale::Codes and its associated Country, Currency and Language modules
Performance Enhancements
o The start up overhead for creating regular expression patterns with
Unicode properties ("\p{...}") has been greatly reduced in most
cases.
o Many string concatenation expressions are now considerably faster,
due to the introduction internally of a "multiconcat" opcode which
combines multiple concatenations, and optionally a "=" or ".=",
into a single action. For example, apart from retrieving $s, $a and
$b, this whole expression is now handled as a single op:
$s .= "a=$a b=$b\n"
As a special case, if the LHS of an assignment is a lexical
variable or "my $s", the op itself handles retrieving the lexical
variable, which is faster.
In general, the more the expression includes a mix of constant
strings and variable expressions, the longer the expression, and
the more it mixes together non-utf8 and utf8 strings, the more
marked the performance improvement. For example on a "x86_64"
system, this code has been benchmarked running four times faster:
my $s;
my $a = "ab\x{100}cde";
my $b = "fghij";
my $c = "\x{101}klmn";
for my $i (1..10_000_000) {
$s = "\x{100}wxyz";
$s .= "foo=$a bar=$b baz=$c";
}
In addition, "sprintf" expressions which have a constant format
containing only %s and "%%" format elements, and which have a fixed
number of arguments, are now also optimised into a "multiconcat"
op.
o The "ref()" builtin is now much faster in boolean context, since it
no longer bothers to construct a temporary string like
"Foo=ARRAY(0x134af48)".
o "keys()" in void and scalar contexts is now more efficient.
o The common idiom of comparing the result of index() with -1 is now
specifically optimised, e.g.
if (index(...) != -1) { ... }
o "for()" loops and similar constructs are now more efficient in most
cases.
o File::Glob has been modified to remove unnecessary backtracking and
recursion, thanks to Russ Cox. See
<https://research.swtch.com/glob> for more details.
o The XS-level "SvTRUE()" API function is now more efficient.
o Various integer-returning ops are now more efficient in
scalar/boolean context.
o Slightly improved performance when parsing stash names. [GH
#15689] <https://github.com/Perl/perl5/issues/15689>
o Calls to "require" for an already loaded module are now slightly
faster. [GH #16175] <https://github.com/Perl/perl5/issues/16175>
o The performance of pattern matching "[[:ascii:]]" and
"[[:^ascii:]]" has been improved significantly except on EBCDIC
platforms.
o Various optimizations have been applied to matching regular
expression patterns, so under the right circumstances, significant
performance gains may be noticed. But in an application with many
varied patterns, little overall improvement likely will be seen.
o Other optimizations have been applied to UTF-8 handling, but these
are not typically a major factor in most applications.
Modules and Pragmata
Key highlights in this release across several modules:
Removal of use vars
The usage of "use vars" has been discouraged since the introduction of
"our" in Perl 5.6.0. Where possible the usage of this pragma has now
been removed from the Perl source code.
This had a slight effect (for the better) on the output of WARNING_BITS
in B::Deparse.
Use of DynaLoader changed to XSLoader in many modules
XSLoader is more modern, and most modules already require perl 5.6 or
greater, so no functionality is lost by switching. In some cases, we
have also made changes to the local implementation that may not be
reflected in the version on CPAN due to a desire to maintain more
backwards compatibility.
Updated Modules and Pragmata
o Archive::Tar has been upgraded from version 2.24 to 2.30.
This update also handled CVE-2018-12015: directory traversal
vulnerability. [cpan #125523]
<https://rt.cpan.org/Ticket/Display.html?id=125523>
o arybase has been upgraded from version 0.12 to 0.15.
o Attribute::Handlers has been upgraded from version 0.99 to 1.01.
o attributes has been upgraded from version 0.29 to 0.33.
o B has been upgraded from version 1.68 to 1.74.
o B::Concise has been upgraded from version 0.999 to 1.003.
o B::Debug has been upgraded from version 1.24 to 1.26.
NOTE: B::Debug is deprecated and may be removed from a future
version of Perl.
o B::Deparse has been upgraded from version 1.40 to 1.48.
It includes many bug fixes, and in particular, it now deparses
variable attributes correctly:
my $x :foo; # used to deparse as
# 'attributes'->import('main', \$x, 'foo'), my $x;
o base has been upgraded from version 2.25 to 2.27.
o bignum has been upgraded from version 0.47 to 0.49.
o blib has been upgraded from version 1.06 to 1.07.
o bytes has been upgraded from version 1.05 to 1.06.
o Carp has been upgraded from version 1.42 to 1.50.
If a package on the call stack contains a constant named "ISA",
Carp no longer throws a "Not a GLOB reference" error.
Carp, when generating stack traces, now attempts to work around
longstanding bugs resulting from Perl's non-reference-counted
stack. [GH #9282] <https://github.com/Perl/perl5/issues/9282>
Carp has been modified to avoid assuming that objects cannot be
overloaded without the overload module loaded (this can happen with
objects created by XS modules). Previously, infinite recursion
would result if an XS-defined overload method itself called Carp.
[GH #16407] <https://github.com/Perl/perl5/issues/16407>
Carp now avoids using "overload::StrVal", partly because older
versions of overload (included with perl 5.14 and earlier) load
Scalar::Util at run time, which will fail if Carp has been invoked
after a syntax error.
o charnames has been upgraded from version 1.44 to 1.45.
o Compress::Raw::Zlib has been upgraded from version 2.074 to 2.076.
This addresses a security vulnerability in older versions of the
'zlib' library (which is bundled with Compress-Raw-Zlib).
o Config::Extensions has been upgraded from version 0.01 to 0.02.
o Config::Perl::V has been upgraded from version 0.28 to 0.29.
o CPAN has been upgraded from version 2.18 to 2.20.
o Data::Dumper has been upgraded from version 2.167 to 2.170.
Quoting of glob names now obeys the Useqq option [GH #13274]
<https://github.com/Perl/perl5/issues/13274>.
Attempts to set an option to "undef" through a combined
getter/setter method are no longer mistaken for getter calls [GH
#12135] <https://github.com/Perl/perl5/issues/12135>.
o Devel::Peek has been upgraded from version 1.26 to 1.27.
o Devel::PPPort has been upgraded from version 3.35 to 3.40.
Devel::PPPort has moved from cpan-first to perl-first maintenance
Primary responsibility for the code in Devel::PPPort has moved into
core perl. In a practical sense there should be no change except
that hopefully it will stay more up to date with changes made to
symbols in perl, rather than needing to be updated after the fact.
o Digest::SHA has been upgraded from version 5.96 to 6.01.
o DirHandle has been upgraded from version 1.04 to 1.05.
o DynaLoader has been upgraded from version 1.42 to 1.45.
Its documentation now shows the use of "__PACKAGE__" and direct
object syntax [GH #16190]
<https://github.com/Perl/perl5/issues/16190>.
o Encode has been upgraded from version 2.88 to 2.97.
o encoding has been upgraded from version 2.19 to 2.22.
o Errno has been upgraded from version 1.28 to 1.29.
o experimental has been upgraded from version 0.016 to 0.019.
o Exporter has been upgraded from version 5.72 to 5.73.
o ExtUtils::CBuilder has been upgraded from version 0.280225 to
0.280230.
o ExtUtils::Constant has been upgraded from version 0.23 to 0.25.
o ExtUtils::Embed has been upgraded from version 1.34 to 1.35.
o ExtUtils::Install has been upgraded from version 2.04 to 2.14.
o ExtUtils::MakeMaker has been upgraded from version 7.24 to 7.34.
o ExtUtils::Miniperl has been upgraded from version 1.06 to 1.08.
o ExtUtils::ParseXS has been upgraded from version 3.34 to 3.39.
o ExtUtils::Typemaps has been upgraded from version 3.34 to 3.38.
o ExtUtils::XSSymSet has been upgraded from version 1.3 to 1.4.
o feature has been upgraded from version 1.47 to 1.52.
o fields has been upgraded from version 2.23 to 2.24.
o File::Copy has been upgraded from version 2.32 to 2.33.
It will now use the sub-second precision variant of utime()
supplied by Time::HiRes where available. [GH #16225]
<https://github.com/Perl/perl5/issues/16225>.
o File::Fetch has been upgraded from version 0.52 to 0.56.
o File::Glob has been upgraded from version 1.28 to 1.31.
o File::Path has been upgraded from version 2.12_01 to 2.15.
o File::Spec and Cwd have been upgraded from version 3.67 to 3.74.
o File::stat has been upgraded from version 1.07 to 1.08.
o FileCache has been upgraded from version 1.09 to 1.10.
o Filter::Simple has been upgraded from version 0.93 to 0.95.
o Filter::Util::Call has been upgraded from version 1.55 to 1.58.
o GDBM_File has been upgraded from version 1.15 to 1.17.
Its documentation now explains that "each" and "delete" don't mix
in hashes tied to this module [GH #12894]
<https://github.com/Perl/perl5/issues/12894>.
It will now retry opening with an acceptable block size if asking
gdbm to default the block size failed [GH #13232]
<https://github.com/Perl/perl5/issues/13232>.
o Getopt::Long has been upgraded from version 2.49 to 2.5.
o Hash::Util::FieldHash has been upgraded from version 1.19 to 1.20.
o I18N::Langinfo has been upgraded from version 0.13 to 0.17.
This module is now available on all platforms, emulating the system
nl_langinfo(3) on systems that lack it. Some caveats apply, as
detailed in its documentation, the most severe being that, except
for MS Windows, the "CODESET" item is not implemented on those
systems, always returning "".
It now sets the UTF-8 flag in its returned scalar if the string
contains legal non-ASCII UTF-8, and the locale is UTF-8 [GH #15131]
<https://github.com/Perl/perl5/issues/15131>.
This update also fixes a bug in which the underlying locale was
ignored for the "RADIXCHAR" (always was returned as a dot) and the
"THOUSEP" (always empty). Now the locale-appropriate values are
returned.
o I18N::LangTags has been upgraded from version 0.42 to 0.43.
o if has been upgraded from version 0.0606 to 0.0608.
o IO has been upgraded from version 1.38 to 1.39.
o IO::Socket::IP has been upgraded from version 0.38 to 0.39.
o IPC::Cmd has been upgraded from version 0.96 to 1.00.
o JSON::PP has been upgraded from version 2.27400_02 to 2.97001.
o The "libnet" distribution has been upgraded from version 3.10 to
3.11.
o List::Util has been upgraded from version 1.46_02 to 1.49.
o Locale::Codes has been upgraded from version 3.42 to 3.56.
NOTE: Locale::Codes scheduled to be removed from core in Perl 5.30.
o Locale::Maketext has been upgraded from version 1.28 to 1.29.
o Math::BigInt has been upgraded from version 1.999806 to 1.999811.
o Math::BigInt::FastCalc has been upgraded from version 0.5005 to
0.5006.
o Math::BigRat has been upgraded from version 0.2611 to 0.2613.
o Module::CoreList has been upgraded from version 5.20170530 to
5.20180622.
o mro has been upgraded from version 1.20 to 1.22.
o Net::Ping has been upgraded from version 2.55 to 2.62.
o NEXT has been upgraded from version 0.67 to 0.67_01.
o ODBM_File has been upgraded from version 1.14 to 1.15.
o Opcode has been upgraded from version 1.39 to 1.43.
o overload has been upgraded from version 1.28 to 1.30.
o PerlIO::encoding has been upgraded from version 0.25 to 0.26.
o PerlIO::scalar has been upgraded from version 0.26 to 0.29.
o PerlIO::via has been upgraded from version 0.16 to 0.17.
o Pod::Functions has been upgraded from version 1.11 to 1.13.
o Pod::Html has been upgraded from version 1.2202 to 1.24.
A title for the HTML document will now be automatically generated
by default from a "NAME" section in the POD document, as it used to
be before the module was rewritten to use Pod::Simple::XHTML to do
the core of its job [GH #11954]
<https://github.com/Perl/perl5/issues/11954>.
o Pod::Perldoc has been upgraded from version 3.28 to 3.2801.
o The "podlators" distribution has been upgraded from version 4.09 to
4.10.
Man page references and function names now follow the Linux man
page formatting standards, instead of the Solaris standard.
o POSIX has been upgraded from version 1.76 to 1.84.
Some more cautions were added about using locale-specific functions
in threaded applications.
o re has been upgraded from version 0.34 to 0.36.
o Scalar::Util has been upgraded from version 1.46_02 to 1.50.
o SelfLoader has been upgraded from version 1.23 to 1.25.
o Socket has been upgraded from version 2.020_03 to 2.027.
o sort has been upgraded from version 2.02 to 2.04.
o Storable has been upgraded from version 2.62 to 3.08.
o Sub::Util has been upgraded from version 1.48 to 1.49.
o subs has been upgraded from version 1.02 to 1.03.
o Sys::Hostname has been upgraded from version 1.20 to 1.22.
o Term::ReadLine has been upgraded from version 1.16 to 1.17.
o Test has been upgraded from version 1.30 to 1.31.
o Test::Harness has been upgraded from version 3.38 to 3.42.
o Test::Simple has been upgraded from version 1.302073 to 1.302133.
o threads has been upgraded from version 2.15 to 2.22.
The documentation now better describes the problems that arise when
returning values from threads, and no longer warns about creating
threads in "BEGIN" blocks. [GH #11563]
<https://github.com/Perl/perl5/issues/11563>
o threads::shared has been upgraded from version 1.56 to 1.58.
o Tie::Array has been upgraded from version 1.06 to 1.07.
o Tie::StdHandle has been upgraded from version 4.4 to 4.5.
o Time::gmtime has been upgraded from version 1.03 to 1.04.
o Time::HiRes has been upgraded from version 1.9741 to 1.9759.
o Time::localtime has been upgraded from version 1.02 to 1.03.
o Time::Piece has been upgraded from version 1.31 to 1.3204.
o Unicode::Collate has been upgraded from version 1.19 to 1.25.
o Unicode::Normalize has been upgraded from version 1.25 to 1.26.
o Unicode::UCD has been upgraded from version 0.68 to 0.70.
The function "num" now accepts an optional parameter to help in
diagnosing error returns.
o User::grent has been upgraded from version 1.01 to 1.02.
o User::pwent has been upgraded from version 1.00 to 1.01.
o utf8 has been upgraded from version 1.19 to 1.21.
o vars has been upgraded from version 1.03 to 1.04.
o version has been upgraded from version 0.9917 to 0.9923.
o VMS::DCLsym has been upgraded from version 1.08 to 1.09.
o VMS::Stdio has been upgraded from version 2.41 to 2.44.
o warnings has been upgraded from version 1.37 to 1.42.
It now includes new functions with names ending in "_at_level",
allowing callers to specify the exact call frame. [GH #16257]
<https://github.com/Perl/perl5/issues/16257>
o XS::Typemap has been upgraded from version 0.15 to 0.16.
o XSLoader has been upgraded from version 0.27 to 0.30.
Its documentation now shows the use of "__PACKAGE__", and direct
object syntax for example "DynaLoader" usage [GH #16190]
<https://github.com/Perl/perl5/issues/16190>.
Platforms that use "mod2fname" to edit the names of loadable
libraries now look for bootstrap (.bs) files under the correct,
non-edited name.
Removed Modules and Pragmata
o The "VMS::stdio" compatibility shim has been removed.
Documentation
Changes to Existing Documentation
We have attempted to update the documentation to reflect the changes
listed in this document. If you find any we have missed, send email to
perlbug@perl.org <mailto:perlbug@perl.org>.
Additionally, the following selected changes have been made:
perlapi
o The API functions "perl_parse()", "perl_run()", and
"perl_destruct()" are now documented comprehensively, where
previously the only documentation was a reference to the perlembed
tutorial.
o The documentation of "newGIVENOP()" has been belatedly updated to
account for the removal of lexical $_.
o The API functions "newCONSTSUB()" and "newCONSTSUB_flags()" are
documented much more comprehensively than before.
perldata
o The section "Truth and Falsehood" in perlsyn has been moved into
perldata.
perldebguts
o The description of the conditions under which "DB::sub()" will be
called has been clarified. [GH #16055]
<https://github.com/Perl/perl5/issues/16055>
perldiag
o "Variable length lookbehind not implemented in regex m/%s/" in
perldiag
This now gives more ideas as to workarounds to the issue that was
introduced in Perl 5.18 (but not documented explicitly in its
perldelta) for the fact that some Unicode "/i" rules cause a few
sequences such as
(?<!st)
to be considered variable length, and hence disallowed.
o "Use of state $_ is experimental" in perldiag
This entry has been removed, as the experimental support of this
construct was removed in perl 5.24.0.
o The diagnostic "Initialization of state variables in list context
currently forbidden" has changed to "Initialization of state
variables in list currently forbidden", because list-context
initialization of single aggregate state variables is now
permitted.
perlembed
o The examples in perlembed have been made more portable in the way
they exit, and the example that gets an exit code from the embedded
Perl interpreter now gets it from the right place. The examples
that pass a constructed argv to Perl now show the mandatory null
"argv[argc]".
o An example in perlembed used the string value of "ERRSV" as a
format string when calling croak(). If that string contains format
codes such as %s this could crash the program.
This has been changed to a call to croak_sv().
An alternative could have been to supply a trivial format string:
croak("%s", SvPV_nolen(ERRSV));
or as a special case for "ERRSV" simply:
croak(NULL);
perlfunc
o There is now a note that warnings generated by built-in functions
are documented in perldiag and warnings. [GH #12642]
<https://github.com/Perl/perl5/issues/12642>
o The documentation for the "exists" operator no longer says that
autovivification behaviour "may be fixed in a future release".
We've determined that we're not going to change the default
behaviour. [GH #15231]
<https://github.com/Perl/perl5/issues/15231>
o A couple of small details in the documentation for the "bless"
operator have been clarified. [GH #14684]
<https://github.com/Perl/perl5/issues/14684>
o The description of @INC hooks in the documentation for "require"
has been corrected to say that filter subroutines receive a useless
first argument. [GH #12569]
<https://github.com/Perl/perl5/issues/12569>
o The documentation of "ref" has been rewritten for clarity.
o The documentation of "use" now explains what syntactically
qualifies as a version number for its module version checking
feature.
o The documentation of "warn" has been updated to reflect that since
Perl 5.14 it has treated complex exception objects in a manner
equivalent to "die". [GH #13641]
<https://github.com/Perl/perl5/issues/13641>
o The documentation of "die" and "warn" has been revised for clarity.
o The documentation of "each" has been improved, with a slightly more
explicit description of the sharing of iterator state, and with
caveats regarding the fragility of while-each loops. [GH #16334]
<https://github.com/Perl/perl5/issues/16334>
o Clarification to "require" was added to explain the differences
between
require Foo::Bar;
require "Foo/Bar.pm";
perlgit
o The precise rules for identifying "smoke-me" branches are now
stated.
perlguts
o The section on reference counting in perlguts has been heavily
revised, to describe references in the way a programmer needs to
think about them rather than in terms of the physical data
structures.
o Improve documentation related to UTF-8 multibytes.
perlintern
o The internal functions "newXS_len_flags()" and "newATTRSUB_x()" are
now documented.
perlobj
o The documentation about "DESTROY" methods has been corrected,
updated, and revised, especially in regard to how they interact
with exceptions. [GH #14083]
<https://github.com/Perl/perl5/issues/14083>
perlop
o The description of the "x" operator in perlop has been clarified.
[GH #16253] <https://github.com/Perl/perl5/issues/16253>
o perlop has been updated to note that "qw"'s whitespace rules differ
from that of "split"'s in that only ASCII whitespace is used.
o The general explanation of operator precedence and associativity
has been corrected and clarified. [GH #15153]
<https://github.com/Perl/perl5/issues/15153>
o The documentation for the "\" referencing operator now explains the
unusual context that it supplies to its operand. [GH #15932]
<https://github.com/Perl/perl5/issues/15932>
perlrequick
o Clarifications on metacharacters and character classes
perlretut
o Clarify metacharacters.
perlrun
o Clarify the differences between -M and -m. [GH #15998]
<https://github.com/Perl/perl5/issues/15998>
perlsec
o The documentation about set-id scripts has been updated and
revised. [GH #10289] <https://github.com/Perl/perl5/issues/10289>
o A section about using "sudo" to run Perl scripts has been added.
perlsyn
o The section "Truth and Falsehood" in perlsyn has been removed from
that document, where it didn't belong, and merged into the existing
paragraph on the same topic in perldata.
o The means to disambiguate between code blocks and hash
constructors, already documented in perlref, are now documented in
perlsyn too. [GH #15918]
<https://github.com/Perl/perl5/issues/15918>
perluniprops
o perluniprops has been updated to note that "\p{Word}" now includes
code points matching the "\p{Join_Control}" property. The change
to the property was made in Perl 5.18, but not documented until
now. There are currently only two code points that match this
property U+200C (ZERO WIDTH NON-JOINER) and U+200D (ZERO WIDTH
JOINER).
o For each binary table or property, the documentation now includes
which characters in the range "\x00-\xFF" it matches, as well as a
list of the first few ranges of code points matched above that.
perlvar
o The entry for $+ in perlvar has been expanded upon to describe
handling of multiply-named capturing groups.
perlfunc, perlop, perlsyn
o In various places, improve the documentation of the special cases
in the condition expression of a while loop, such as implicit
"defined" and assignment to $_. [GH #16334]
<https://github.com/Perl/perl5/issues/16334>
Diagnostics
The following additions or changes have been made to diagnostic output,
including warnings and fatal error messages. For the complete list of
diagnostic messages, see perldiag.
New Diagnostics
New Errors
o Can't "goto" into a "given" block
(F) A "goto" statement was executed to jump into the middle of a
"given" block. You can't get there from here. See "goto" in
perlfunc.
o Can't "goto" into a binary or list expression
Use of "goto" to jump into the parameter of a binary or list
operator has been prohibited, to prevent crashes and stack
corruption. [GH #15914]
<https://github.com/Perl/perl5/issues/15914>
You may only enter the first argument of an operator that takes a
fixed number of arguments, since this is a case that will not cause
stack corruption. [GH #16415]
<https://github.com/Perl/perl5/issues/16415>
New Warnings
o Old package separator used in string
(W syntax) You used the old package separator, "'", in a variable
named inside a double-quoted string; e.g., "In $name's house".
This is equivalent to "In $name::s house". If you meant the
former, put a backslash before the apostrophe ("In $name\'s
house").
o "Locale '%s' contains (at least) the following characters which
have unexpected meanings: %s The Perl program will use the
expected meanings" in perldiag
Changes to Existing Diagnostics
o A false-positive warning that was issued when using a numerically-
quantified sub-pattern in a recursive regex has been silenced. [GH
#16106] <https://github.com/Perl/perl5/issues/16106>
o The warning about useless use of a concatenation operator in void
context is now generated for expressions with multiple
concatenations, such as "$a.$b.$c", which used to mistakenly not
warn. [GH #3990] <https://github.com/Perl/perl5/issues/3990>
o Warnings that a variable or subroutine "masks earlier declaration
in same ...", or that an "our" variable has been redeclared, have
been moved to a new warnings category "shadow". Previously they
were in category "misc".
o The deprecation warning from "Sys::Hostname::hostname()" saying
that it doesn't accept arguments now states the Perl version in
which the warning will be upgraded to an error. [GH #14662]
<https://github.com/Perl/perl5/issues/14662>
o The perldiag entry for the error regarding a set-id script has been
expanded to make clear that the error is reporting a specific
security vulnerability, and to advise how to fix it.
o The "Unable to flush stdout" error message was missing a trailing
newline. [debian #875361]
Utility Changes
perlbug
o "--help" and "--version" options have been added.
Configuration and Compilation
o C89 requirement
Perl has been documented as requiring a C89 compiler to build since
October 1998. A variety of simplifications have now been made to
Perl's internals to rely on the features specified by the C89
standard. We believe that this internal change hasn't altered the
set of platforms that Perl builds on, but please report a bug if
Perl now has new problems building on your platform.
o On GCC, "-Werror=pointer-arith" is now enabled by default,
disallowing arithmetic on void and function pointers.
o Where an HTML version of the documentation is installed, the HTML
documents now use relative links to refer to each other. Links
from the index page of perlipc to the individual section documents
are now correct. [GH #11941]
<https://github.com/Perl/perl5/issues/11941>
o lib/unicore/mktables now correctly canonicalizes the names of the
dependencies stored in the files it generates.
regen/mk_invlists.pl, unlike the other regen/*.pl scripts, used $0
to name itself in the dependencies stored in the files it
generates. It now uses a literal so that the path stored in the
generated files doesn't depend on how regen/mk_invlists.pl is
invoked.
This lack of canonical names could cause test failures in
t/porting/regen.t. [GH #16446]
<https://github.com/Perl/perl5/issues/16446>
o New probes
HAS_BUILTIN_ADD_OVERFLOW
HAS_BUILTIN_MUL_OVERFLOW
HAS_BUILTIN_SUB_OVERFLOW
HAS_THREAD_SAFE_NL_LANGINFO_L
HAS_LOCALECONV_L
HAS_MBRLEN
HAS_MBRTOWC
HAS_MEMRCHR
HAS_NANOSLEEP
HAS_STRNLEN
HAS_STRTOLD_L
I_WCHAR
Testing
o Testing of the XS-APItest directory is now done in parallel, where
applicable.
o Perl now includes a default .travis.yml file for Travis CI testing
on github mirrors. [GH #14558]
<https://github.com/Perl/perl5/issues/14558>
o The watchdog timer count in re/pat_psycho.t can now be overridden.
This test can take a long time to run, so there is a timer to keep
this in check (currently, 5 minutes). This commit adds checking the
environment variable "PERL_TEST_TIME_OUT_FACTOR"; if set, the time
out setting is multiplied by its value.
o harness no longer waits for 30 seconds when running t/io/openpid.t.
[GH #13535] <https://github.com/Perl/perl5/issues/13535> [GH
#16420] <https://github.com/Perl/perl5/issues/16420>
Packaging
For the past few years we have released perl using three different
archive formats: bzip (".bz2"), LZMA2 (".xz") and gzip (".gz"). Since
xz compresses better and decompresses faster, and gzip is more
compatible and uses less memory, we have dropped the ".bz2" archive
format with this release. (If this poses a problem, do let us know;
see "Reporting Bugs", below.)
Platform Support
Discontinued Platforms
PowerUX / Power MAX OS
Compiler hints and other support for these apparently long-defunct
platforms has been removed.
Platform-Specific Notes
CentOS
Compilation on CentOS 5 is now fixed.
Cygwin
A build with the quadmath library can now be done on Cygwin.
Darwin
Perl now correctly uses reentrant functions, like "asctime_r", on
versions of Darwin that have support for them.
FreeBSD
FreeBSD's /usr/share/mk/sys.mk specifies "-O2" for architectures
other than ARM and MIPS. By default, perl is now compiled with the
same optimization levels.
VMS Several fix-ups for configure.com, marking function VMS has (or
doesn't have).
CRTL features can now be set by embedders before invoking Perl by
using the "decc$feature_set" and "decc$feature_set_value"
functions. Previously any attempt to set features after image
initialization were ignored.
Windows
o Support for compiling perl on Windows using Microsoft Visual
Studio 2017 (containing Visual C++ 14.1) has been added.
o Visual C++ compiler version detection has been improved to work
on non-English language systems.
o We now set $Config{libpth} correctly for 64-bit builds using
Visual C++ versions earlier than 14.1.
Internal Changes
o A new optimisation phase has been added to the compiler,
"optimize_optree()", which does a top-down scan of a complete
optree just before the peephole optimiser is run. This phase is not
currently hookable.
o An "OP_MULTICONCAT" op has been added. At "optimize_optree()" time,
a chain of "OP_CONCAT" and "OP_CONST" ops, together optionally with
an "OP_STRINGIFY" and/or "OP_SASSIGN", are combined into a single
"OP_MULTICONCAT" op. The op is of type "UNOP_AUX", and the aux
array contains the argument count, plus a pointer to a constant
string and a set of segment lengths. For example with
my $x = "foo=$foo, bar=$bar\n";
the constant string would be "foo=, bar=\n" and the segment lengths
would be (4,6,1). If the string contains characters such as "\x80",
whose representation changes under utf8, two sets of strings plus
lengths are precomputed and stored.
o Direct access to "PL_keyword_plugin" is not safe in the presence of
multithreading. A new "wrap_keyword_plugin" function has been added
to allow XS modules to safely define custom keywords even when
loaded from a thread, analogous to "PL_check" / "wrap_op_checker".
o The "PL_statbuf" interpreter variable has been removed.
o The deprecated function "to_utf8_case()", accessible from XS code,
has been removed.
o A new function "is_utf8_invariant_string_loc()" has been added that
is like "is_utf8_invariant_string()" but takes an extra pointer
parameter into which is stored the location of the first variant
character, if any are found.
o A new function, "Perl_langinfo()" has been added. It is an
(almost) drop-in replacement for the system nl_langinfo(3), but
works on platforms that lack that; as well as being more thread-
safe, and hiding some gotchas with locale handling from the caller.
Code that uses this, needn't use localeconv(3) (and be affected by
the gotchas) to find the decimal point, thousands separator, or
currency symbol. See "Perl_langinfo" in perlapi.
o A new API function "sv_rvunweaken()" has been added to complement
"sv_rvweaken()". The implementation was taken from "unweaken" in
Scalar::Util.
o A new flag, "SORTf_UNSTABLE", has been added. This will allow a
future commit to make mergesort unstable when the user specifies
Xno sort stableX, since it has been decided that mergesort should
remain stable by default.
o XS modules can now automatically get reentrant versions of system
functions on threaded perls.
By adding
#define PERL_REENTRANT
near the beginning of an "XS" file, it will be compiled so that
whatever reentrant functions perl knows about on that system will
automatically and invisibly be used instead of the plain, non-
reentrant versions. For example, if you write "getpwnam()" in your
code, on a system that has "getpwnam_r()" all calls to the former
will be translated invisibly into the latter. This does not happen
except on threaded perls, as they aren't needed otherwise. Be
aware that which functions have reentrant versions varies from
system to system.
o The "PERL_NO_OP_PARENT" build define is no longer supported, which
means that perl is now always built with "PERL_OP_PARENT" enabled.
o The format and content of the non-utf8 transliteration table
attached to the "op_pv" field of "OP_TRANS"/"OP_TRANSR" ops has
changed. It's now a "struct OPtrans_map".
o A new compiler "#define", "dTHX_DEBUGGING". has been added. This
is useful for XS or C code that only need the thread context
because their debugging statements that get compiled only under
"-DDEBUGGING" need one.
o A new API function "Perl_setlocale" in perlapi has been added.
o "sync_locale" in perlapi has been revised to return a boolean as to
whether the system was using the global locale or not.
o A new kind of magic scalar, called a "nonelem" scalar, has been
introduced. It is stored in an array to denote a non-existent
element, whenever such an element is accessed in a potential lvalue
context. It replaces the existing "defelem" (deferred element)
magic wherever this is possible, being significantly more
efficient. This means that "some_sub($sparse_array[$nonelem])" no
longer has to create a new magic defelem scalar each time, as long
as the element is within the array.
It partially fixes the rare bug of deferred elements getting out of
synch with their arrays when the array is shifted or unshifted.
[GH #16364] <https://github.com/Perl/perl5/issues/16364>
Selected Bug Fixes
o List assignment ("aassign") could in some rare cases allocate an
entry on the mortals stack and leave the entry uninitialized,
leading to possible crashes. [GH #16017]
<https://github.com/Perl/perl5/issues/16017>
o Attempting to apply an attribute to an "our" variable where a
function of that name already exists could result in a NULL pointer
being supplied where an SV was expected, crashing perl. [perl
#131597] <https://rt.perl.org/Ticket/Display.html?id=131597>
o "split ' '" now correctly handles the argument being split when in
the scope of the "unicode_strings" feature. Previously, when a
string using the single-byte internal representation contained
characters that are whitespace by Unicode rules but not by ASCII
rules, it treated those characters as part of fields rather than as
field separators. [GH #15904]
<https://github.com/Perl/perl5/issues/15904>
o Several built-in functions previously had bugs that could cause
them to write to the internal stack without allocating room for the
item being written. In rare situations, this could have led to a
crash. These bugs have now been fixed, and if any similar bugs are
introduced in future, they will be detected automatically in
debugging builds.
These internal stack usage checks introduced are also done by the
"entersub" operator when calling XSUBs. This means we can report
which XSUB failed to allocate enough stack space. [GH #16126]
<https://github.com/Perl/perl5/issues/16126>
o Using a symbolic ref with postderef syntax as the key in a hash
lookup was yielding an assertion failure on debugging builds. [GH
#16029] <https://github.com/Perl/perl5/issues/16029>
o Array and hash variables whose names begin with a caret now admit
indexing inside their curlies when interpolated into strings, as in
"${^CAPTURE[0]}" to index "@{^CAPTURE}". [GH #16050]
<https://github.com/Perl/perl5/issues/16050>
o Fetching the name of a glob that was previously UTF-8 but wasn't
any longer would return that name flagged as UTF-8. [GH #15971]
<https://github.com/Perl/perl5/issues/15971>
o The perl "sprintf()" function (via the underlying C function
"Perl_sv_vcatpvfn_flags()") has been heavily reworked to fix many
minor bugs, including the integer wrapping of large width and
precision specifiers and potential buffer overruns. It has also
been made faster in many cases.
o Exiting from an "eval", whether normally or via an exception, now
always frees temporary values (possibly calling destructors) before
setting $@. For example:
sub DESTROY { eval { die "died in DESTROY"; } }
eval { bless []; };
# $@ used to be equal to "died in DESTROY" here; it's now "".
o Fixed a duplicate symbol failure with "-flto -mieee-fp" builds.
pp.c defined "_LIB_VERSION" which "-lieee" already defines. [GH
#16086] <https://github.com/Perl/perl5/issues/16086>
o The tokenizer no longer consumes the exponent part of a floating
point number if it's incomplete. [GH #16073]
<https://github.com/Perl/perl5/issues/16073>
o On non-threaded builds, for "m/$null/" where $null is an empty
string is no longer treated as if the "/o" flag was present when
the previous matching match operator included the "/o" flag. The
rewriting used to implement this behavior could confuse the
interpreter. This matches the behaviour of threaded builds. [GH
#14668] <https://github.com/Perl/perl5/issues/14668>
o Parsing a "sub" definition could cause a use after free if the
"sub" keyword was followed by whitespace including newlines (and
comments.) [GH #16097]
<https://github.com/Perl/perl5/issues/16097>
o The tokenizer now correctly adjusts a parse pointer when skipping
whitespace in a "${identifier}" construct. [perl #131949]
<https://rt.perl.org/Public/Bug/Display.html?id=131949>
o Accesses to "${^LAST_FH}" no longer assert after using any of a
variety of I/O operations on a non-glob. [GH #15372]
<https://github.com/Perl/perl5/issues/15372>
o The XS-level "Copy()", "Move()", "Zero()" macros and their variants
now assert if the pointers supplied are "NULL". ISO C considers
supplying NULL pointers to the functions these macros are built
upon as undefined behaviour even when their count parameters are
zero. Based on these assertions and the original bug report three
macro calls were made conditional. [GH #16079]
<https://github.com/Perl/perl5/issues/16079> [GH #16112]
<https://github.com/Perl/perl5/issues/16112>
o Only the "=" operator is permitted for defining defaults for
parameters in subroutine signatures. Previously other assignment
operators, e.g. "+=", were also accidentally permitted. [GH
#16084] <https://github.com/Perl/perl5/issues/16084>
o Package names are now always included in ":prototype" warnings
[perl #131833]
<https://rt.perl.org/Public/Bug/Display.html?id=131833>
o The "je_old_stack_hwm" field, previously only found in the "jmpenv"
structure on debugging builds, has been added to non-debug builds
as well. This fixes an issue with some CPAN modules caused by the
size of this structure varying between debugging and non-debugging
builds. [GH #16122] <https://github.com/Perl/perl5/issues/16122>
o The arguments to the "ninstr()" macro are now correctly
parenthesized.
o A NULL pointer dereference in the "S_regmatch()" function has been
fixed. [perl #132017]
<https://rt.perl.org/Public/Bug/Display.html?id=132017>
o Calling exec PROGRAM LIST with an empty "LIST" has been fixed.
This should call "execvp()" with an empty "argv" array (containing
only the terminating "NULL" pointer), but was instead just
returning false (and not setting $!). [GH #16075]
<https://github.com/Perl/perl5/issues/16075>
o The "gv_fetchmeth_sv" C function stopped working properly in Perl
5.22 when fetching a constant with a UTF-8 name if that constant
subroutine was stored in the stash as a simple scalar reference,
rather than a full typeglob. This has been corrected.
o Single-letter debugger commands followed by an argument which
starts with punctuation (e.g. "p$^V" and "x@ARGV") now work again.
They had been wrongly requiring a space between the command and the
argument. [GH #13342] <https://github.com/Perl/perl5/issues/13342>
o splice now throws an exception ("Modification of a read-only value
attempted") when modifying a read-only array. Until now it had
been silently modifying the array. The new behaviour is consistent
with the behaviour of push and unshift. [GH #15923]
<https://github.com/Perl/perl5/issues/15923>
o "stat()", "lstat()", and file test operators now fail if given a
filename containing a nul character, in the same way that "open()"
already fails.
o "stat()", "lstat()", and file test operators now reliably set $!
when failing due to being applied to a closed or otherwise invalid
file handle.
o File test operators for Unix permission bits that don't exist on a
particular platform, such as "-k" (sticky bit) on Windows, now
check that the file being tested exists before returning the
blanket false result, and yield the appropriate errors if the
argument doesn't refer to a file.
o Fixed a 'read before buffer' overrun when parsing a range starting
with "\N{}" at the beginning of the character set for the
transliteration operator. [GH #16189]
<https://github.com/Perl/perl5/issues/16189>
o Fixed a leaked scalar when parsing an empty "\N{}" at compile-time.
[GH #16189] <https://github.com/Perl/perl5/issues/16189>
o Calling "do $path" on a directory or block device now yields a
meaningful error code in $!. [GH #14841]
<https://github.com/Perl/perl5/issues/14841>
o Regexp substitution using an overloaded replacement value that
provides a tainted stringification now correctly taints the
resulting string. [GH #12495]
<https://github.com/Perl/perl5/issues/12495>
o Lexical sub declarations in "do" blocks such as "do { my sub lex;
123 }" could corrupt the stack, erasing items already on the stack
in the enclosing statement. This has been fixed. [GH #16243]
<https://github.com/Perl/perl5/issues/16243>
o "pack" and "unpack" can now handle repeat counts and lengths that
exceed two billion. [GH #13179]
<https://github.com/Perl/perl5/issues/13179>
o Digits past the radix point in octal and binary floating point
literals now have the correct weight on platforms where a floating
point significand doesn't fit into an integer type.
o The canonical truth value no longer has a spurious special meaning
as a callable subroutine. It used to be a magic placeholder for a
missing "import" or "unimport" method, but is now treated like any
other string 1. [GH #14902]
<https://github.com/Perl/perl5/issues/14902>
o "system" now reduces its arguments to strings in the parent
process, so any effects of stringifying them (such as overload
methods being called or warnings being emitted) are visible in the
way the program expects. [GH #13561]
<https://github.com/Perl/perl5/issues/13561>
o The "readpipe()" built-in function now checks at compile time that
it has only one parameter expression, and puts it in scalar
context, thus ensuring that it doesn't corrupt the stack at
runtime. [GH #2793] <https://github.com/Perl/perl5/issues/2793>
o "sort" now performs correct reference counting when aliasing $a and
$b, thus avoiding premature destruction and leakage of scalars if
they are re-aliased during execution of the sort comparator. [GH
#11422] <https://github.com/Perl/perl5/issues/11422>
o "reverse" with no operand, reversing $_ by default, is no longer in
danger of corrupting the stack. [GH #16291]
<https://github.com/Perl/perl5/issues/16291>
o "exec", "system", et al are no longer liable to have their argument
lists corrupted by reentrant calls and by magic such as tied
scalars. [GH #15660] <https://github.com/Perl/perl5/issues/15660>
o Perl's own "malloc" no longer gets confused by attempts to allocate
more than a gigabyte on a 64-bit platform. [GH #13273]
<https://github.com/Perl/perl5/issues/13273>
o Stacked file test operators in a sort comparator expression no
longer cause a crash. [GH #15626]
<https://github.com/Perl/perl5/issues/15626>
o An identity "tr///" transformation on a reference is no longer
mistaken for that reference for the purposes of deciding whether it
can be assigned to. [GH #15812]
<https://github.com/Perl/perl5/issues/15812>
o Lengthy hexadecimal, octal, or binary floating point literals no
longer cause undefined behaviour when parsing digits that are of
such low significance that they can't affect the floating point
value. [GH #16114] <https://github.com/Perl/perl5/issues/16114>
o "open $$scalarref..." and similar invocations no longer leak the
file handle. [GH #12593]
<https://github.com/Perl/perl5/issues/12593>
o Some convoluted kinds of regexp no longer cause an arithmetic
overflow when compiled. [GH #16113]
<https://github.com/Perl/perl5/issues/16113>
o The default typemap, by avoiding "newGVgen", now no longer leaks
when XSUBs return file handles ("PerlIO *" or "FILE *"). [GH
#12593] <https://github.com/Perl/perl5/issues/12593>
o Creating a "BEGIN" block as an XS subroutine with a prototype no
longer crashes because of the early freeing of the subroutine.
o The "printf" format specifier "%.0f" no longer rounds incorrectly
[GH #9125] <https://github.com/Perl/perl5/issues/9125>, and now
shows the correct sign for a negative zero.
o Fixed an issue where the error "Scalar value @arrayname[0] better
written as $arrayname" would give an error "Cannot printf Inf with
'c'" when arrayname starts with "Inf". [GH #16335]
<https://github.com/Perl/perl5/issues/16335>
o The Perl implementation of "getcwd()" in "Cwd" in the PathTools
distribution now behaves the same as XS implementation on errors:
it returns an error, and sets $!. [GH #16338]
<https://github.com/Perl/perl5/issues/16338>
o Vivify array elements when putting them on the stack. Fixes [GH
#5310] <https://github.com/Perl/perl5/issues/5310> (reported in
April 2002).
o Fixed parsing of braced subscript after parens. Fixes [GH #4688]
<https://github.com/Perl/perl5/issues/4688> (reported in December
2001).
o "tr/non_utf8/long_non_utf8/c" could give the wrong results when the
length of the replacement character list was greater than 0x7fff.
o "tr/non_utf8/non_utf8/cd" failed to add the implied
"\x{100}-\x{7fffffff}" to the search character list.
o Compilation failures within "perl-within-perl" constructs, such as
with string interpolation and the right part of "s///e", now cause
compilation to abort earlier.
Previously compilation could continue in order to report other
errors, but the failed sub-parse could leave partly parsed
constructs on the parser shift-reduce stack, confusing the parser,
leading to perl crashes. [GH #14739]
<https://github.com/Perl/perl5/issues/14739>
o On threaded perls where the decimal point (radix) character is not
a dot, it has been possible for a race to occur between threads
when one needs to use the real radix character (such as with
"sprintf"). This has now been fixed by use of a mutex on systems
without thread-safe locales, and the problem just doesn't come up
on those with thread-safe locales.
o Errors while compiling a regex character class could sometime
trigger an assertion failure. [GH #16172]
<https://github.com/Perl/perl5/issues/16172>
Acknowledgements
Perl 5.28.0 represents approximately 13 months of development since
Perl 5.26.0 and contains approximately 730,000 lines of changes across
2,200 files from 77 authors.
Excluding auto-generated files, documentation and release tools, there
were approximately 580,000 lines of changes to 1,300 .pm, .t, .c and .h
files.
Perl continues to flourish into its fourth decade thanks to a vibrant
community of users and developers. The following people are known to
have contributed the improvements that became Perl 5.28.0:
Aaron Crane, Abigail, AEvar Arnfjoer` Bjarmason, Alberto Simo~es,
Alexandr Savca, Andrew Fresh, Andy Dougherty, Andy Lester, Aristotle
Pagaltzis, Ask Bjorn Hansen, Chris 'BinGOs' Williams, Craig A. Berry,
Dagfinn Ilmari Mannsaaker, Dan Collins, Daniel Dragan, David Cantrell,
David Mitchell, Dmitry Ulanov, Dominic Hargreaves, E. Choroba, Eric
Herman, Eugen Konkov, Father Chrysostomos, Gene Sullivan, George
Hartzell, Graham Knop, Harald Joerg, H.Merijn Brand, Hugo van der
Sanden, Jacques Germishuys, James E Keenan, Jarkko Hietaniemi, Jerry D.
Hedden, J. Nick Koston, John Lightsey, John Peacock, John P. Linderman,
John SJ Anderson, Karen Etheridge, Karl Williamson, Ken Brown, Ken
Cotterill, Leon Timmermans, Lukas Mai, Marco Fontani, Marc-Philip
Werner, Matthew Horsfall, Neil Bowers, Nicholas Clark, Nicolas R., Niko
Tyni, Pali, Paul Marquess, Peter John Acklam, Reini Urban, Renee
Baecker, Ricardo Signes, Robin Barker, Sawyer X, Scott Lanning, Sergey
Aleynikov, Shirakata Kentaro, Shoichi Kaji, Slaven Rezic, Smylers,
Steffen Mueller, Steve Hay, Sullivan Beck, Thomas Sibley, Todd Rinaldo,
Tomasz Konojacki, Tom Hukins, Tom Wyant, Tony Cook, Vitali Peil, Yves
Orton, Zefram.
The list above is almost certainly incomplete as it is automatically
generated from version control history. In particular, it does not
include the names of the (very much appreciated) contributors who
reported issues to the Perl bug tracker.
Many of the changes included in this version originated in the CPAN
modules included in Perl's core. We're grateful to the entire CPAN
community for helping Perl to flourish.
For a more complete list of all of Perl's historical contributors,
please see the AUTHORS file in the Perl source distribution.
Reporting Bugs
If you find what you think is a bug, you might check the perl bug
database at <https://rt.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.
If the bug you are reporting has security implications which make it
inappropriate to send to a publicly archived mailing list, then see
"SECURITY VULNERABILITY CONTACT INFORMATION" in perlsec for details of
how to report the issue.
Give Thanks
If you wish to thank the Perl 5 Porters for the work we had done in
Perl 5, you can do so by running the "perlthanks" program:
perlthanks
This will send an email to the Perl 5 Porters list with your show of
thanks.
SEE ALSO
The Changes file for an explanation of how to view 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.
perl v5.34.0 2021-05-04 PERL5280DELTA(1pm)
perl 5.34.0 - Generated Fri Feb 25 07:39:00 CST 2022