| PERL5400DELTA(1) | Perl Programmers Reference Guide | PERL5400DELTA(1) |
perldelta - what is new for perl v5.40.0
This document describes differences between the 5.38.0 release and the 5.40.0 release.
When using the new "class" feature, code inside a method, "ADJUST" block or field initializer expression is now permitted to use the new "__CLASS__" keyword. This yields a class name, similar to "__PACKAGE__", but whereas that gives the compile-time package that the code appears in, the "__CLASS__" keyword is aware of the actual run-time class that the object instance is a member of. This makes it useful for method dispatch on that class, especially during constructors, where access to $self is not permitted.
For more information, see "__CLASS__" in perlfunc.
When using the "class" feature, field variables can now take a ":reader" attribute. This requests that an accessor method be automatically created that simply returns the value of the field variable from the given instance.
field $name :reader;
Is equivalent to
field $name;
method name () { return $name; }
An alternative name can also be provided:
field $name :reader(get_name);
For more detail, see ":reader" in perlclass.
When processing command-line options, perl now allows a space between the "-M" switch and the name of the module after it.
$ perl -M Data::Dumper=Dumper -E 'say Dumper [1,2,3]'
This matches the existing behaviour of the "-I" option.
In Perl 5.36, a deprecation warning was added when downgrading a "use VERSION" declaration from one above version 5.11, to below. This has now been made a fatal error.
Additionally, it is now a fatal error to issue a subsequent "use VERSION" declaration when another is in scope, when either version is 5.39 or above. This is to avoid complications surrounding imported lexical functions from builtin. A deprecation warning has also been added for any other subsequent "use VERSION" declaration below version 5.39, to warn that it will no longer be permitted in Perl version 5.44.
Two new functions, "inf" and "nan", have been added to the "builtin" namespace. These act like constants that yield the floating-point infinity and Not-a-Number value respectively.
Perl has always had three low-precedence logical operators "and", "or" and "xor", as well as three high-precedence bitwise versions "&", "^" and "|". Until this release, while the medium-precedence logical operators of "&&" and "||" were also present, there was no exclusive-or equivalent. This release of Perl adds the final "^^" operator, completing the set.
$x ^^ $y and say "One of x or y is true, but not both";
Prior to this release, the "try"/"catch" feature for handling errors was considered experimental. Introduced in Perl version 5.34.0, this is now considered a stable language feature and its use no longer prints a warning. It still must be enabled with the 'try' feature.
See "Try Catch Exception Handling" in perlsyn.
Prior to this release, iterating over multiple values at a time with "for" was considered experimental. Introduced in Perl version 5.36.0, this is now considered a stable language feature and its use no longer prints a warning. See "Compound Statements" in perlsyn.
Prior to this release, the builtin module and all of its functions were considered experimental. Introduced in Perl version 5.36.0, this module is now considered stable its use no longer prints a warning. However, several of its functions are still considered experimental.
The latest version feature bundle now contains the recently-stablized feature "try". As this feature bundle is used by the "-E" commandline switch, these are immediately available in "-E" scripts.
In addition to importing a feature bundle, "use v5.40;" (or later versions) imports the corresponding builtin version bundle.
This vulnerability was reported directly to the Perl security team by Nathan Mills "the.true.nathan.mills@gmail.com".
A crafted regular expression when compiled by perl 5.30.0 through 5.38.0 can cause a one-byte attacker controlled buffer overflow in a heap allocated buffer.
This vulnerability was reported to the Intel Product Security Incident Response Team (PSIRT) by GitHub user ycdxsb <https://github.com/ycdxsb/WindowsPrivilegeEscalation>. PSIRT then reported it to the Perl security team.
Perl for Windows relies on the system path environment variable to find the shell ("cmd.exe"). When running an executable which uses Windows Perl interpreter, Perl attempts to find and execute "cmd.exe" within the operating system. However, due to path search order issues, Perl initially looks for cmd.exe in the current working directory.
An attacker with limited privileges can exploit this behavior by placing "cmd.exe" in locations with weak permissions, such as "C:\ProgramData". By doing so, when an administrator attempts to use this executable from these compromised locations, arbitrary code can be executed.
Previously "reset EXPR" did not call set magic when clearing scalar variables. This meant that changes did not propagate to the underlying internal state where needed, such as for $^W, and did not result in an exception where the underlying magic would normally throw an exception, such as for $1.
This means code that had no effect before may now actually have an effect, including possibly throwing an exception.
"reset EXPR" already called set magic when modifying arrays and hashes.
This has no effect on plain "reset" used to reset one-match searches as with "m?pattern?".
[GH #20763 <https://github.com/Perl/perl5/issues/20763>]
Historically, it has been possible to call the "import" or "unimport" method of any class, including ones which have not been defined, with an argument and not experience an error. For instance, this code will not throw an error in Perl 5.38:
Class::That::Does::Not::Exist->import("foo");
However, as of Perl 5.39.1 this is deprecated and will issue a warning. Note that calling these methods with no arguments continues to silently succeed and do nothing. For instance,
Class::That::Does::Not::Exist->import();
will continue to not throw an error. This is because every class implicitly inherits from the class UNIVERSAL which now defines an "import" method. In older perls there was no such method defined, and instead the method calls for "import" and "unimport" were special cased to not throw errors if there was no such method defined.
This change has been added because it makes it easier to detect case typos in "use" statements when running on case-insensitive file systems. For instance, on Windows or other platforms with case-insensitive file systems on older perls the following code
use STRICT 'refs';
would silently do nothing as the module is actually called strict.pm, not STRICT.pm, so it would be loaded but its import method would never be called. It will also detect cases where a user passes an argument when using a package that does not provide its own import, for instance most "pure" class definitions do not define an import method.
The "return" operator syntax now rejects indirect objects. In most cases this would compile and even run, but wasn't documented and could produce confusing results, for example:
# note that sum hasn't been defined
sub sum_positive {
return sum grep $_ > 0, @_;
# unexpectedly parsed as:
# return *sum, grep $_ > 0, @_;
# ... with the bareword acting like an extra (typeglob) argument
}
say for sum_positive(-1, 2, 3)
produced:
*main::sum
2
3
[GH #21716 <https://github.com/Perl/perl5/issues/21716>]
Under "no feature "bareword_filehandles"" bareword file handles continued to be resolved in method calls:
open FH, "<", $somefile or die;
no feature 'bareword_filehandles';
FH->binmode;
This has been fixed, so the:
FH->binmode;
will attempt to resolve "FH" as a class, typically resulting in a runtime error.
The standard file handles such as "STDOUT" continue to be resolved as a handle:
no feature 'bareword_filehandles';
STDOUT->flush; # continues to work
Note that once perl resolves a bareword name as a class it will continue to do so:
package SomeClass {
sub somemethod{}
}
open SomeClass, "<", "somefile" or die;
# SomeClass resolved as a handle
SomeClass->binmode;
{
no feature "bareword_filehandles";
SomeClass->somemethod;
}
# SomeClass resolved as a class
SomeClass->binmode;
[GH #19426 <https://github.com/Perl/perl5/issues/19426>]
This module is a dependency of Test2::Suite.
This distribution contains a comprehensive set of test tools for writing unit tests. It is the successor to Test::More and similar modules. Its inclusion in the Perl core means that CPAN module tests can be written using this suite of tools without extra dependencies.
builtin now accepts a version bundle as an input argument, requesting it to import all of the functions that are considered a stable part of the module at the given Perl version. For example:
use builtin ':5.40';
Added the load_module() builtin function as per PPC 0006 <https://github.com/Perl/PPCs/blob/main/ppcs/ppc0006-load-module.md>.
The "osvers" and "archname" baked into the module to ensure Errno is loaded by the perl that built it are now more comprehensively escaped. [GH #21135 <https://github.com/Perl/perl5/issues/21135>]
The old module documentation stub has been greatly expanded and revised.
Adds support for the "O_TMPFILE" flag on Linux.
It now documents the ":all" feature bundle, and suggests a reason why you may not wish to use it.
Documentation and test improvements only; no change in functionality.
It now handles the additional locale categories that Linux defines beyond those in the POSIX Standard.
This fixes what is returned for the "ALT_DIGITS" item, which has never before worked properly in Perl.
Fixed "IO::Handle/blocking" on Windows, which has been non-functional since IO 1.32. [GH #17455 <https://github.com/Perl/perl5/issues/17455>]
Made parsing of the "l" command arguments saner. [GH #21350 <https://github.com/Perl/perl5/issues/21350>]
The "mktime" function now works correctly on 32-bit platforms even if the platform's "time_t" type is larger than 32 bits. [GH #21551 <https://github.com/Perl/perl5/issues/21551>]
The "T_SIGNO" and "T_FD" typemap entries have been fixed so they work with any variable name, rather than just the hardcoded "sig" and "fd".
The mappings for "Mode_t", "pid_t", "Uid_t", "Gid_t" and "Time_t" have been updated to be integer types; previously they were "NV" floating-point.
Adjusted the signbit() on NaN test to handle the unusual bit pattern returned for NaN by Oracle Developer Studio's compiler. [GH #21533 <https://github.com/Perl/perl5/issues/21533>]
An internal error has been made slightly more verbose ("Out of memory in perl:threads:ithread_create").
Old compatibility code for perl 5.005 that was no longer functional has been removed.
We have attempted to update the documentation to reflect the changes listed in this document. If you find any we have missed, open an issue at <https://github.com/Perl/perl5/issues>.
Additionally, the following selected changes have been made:
perlapi
perlclass
perlfunc
perlguts
perlclib
perlhacktips
perllol
perlre
perlref
perlop
perlport
perlvar
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 Errors
(F) A "__CLASS__" expression yields the class name of the object instance executing the current method, and therefore it can only be placed inside an actual method (or method-like expression, such as a field initializer expression).
(F) You called PerlIO::get_layers() with an unknown argument. Legal arguments are provided in key/value pairs, with the keys being one of "input", "output" or "detail", followed by a boolean.
(F) You asked UNIVERSAL to export something, but UNIVERSAL is the base class for all classes and contains no exportable symbols.
(F) You attempted to "use builtin :ver" for a version number that is either older than 5.39 (when the ability was added), or newer than the current perl version.
(F) A version number that is used to specify an import bundle during a "use builtin ..." statement must be formatted as ":MAJOR.MINOR" with an optional third component, which is ignored. Each component must be a number of 1 to 3 digits. No other characters are permitted. The value that was specified does not conform to these rules.
(F) While certain operators allow you to specify a filehandle or an "indirect object" before the argument list, "return" isn't one of them.
(F) An attempt was made to extend a string beyond the largest possible memory allocation by assigning to vec() called with a large second argument.
(This case used to throw a generic "Out of memory!" error.)
(F) An attempt was made to create an object of a class where the start of the class definition has been seen, but the class has not been completed.
This can happen for a failed eval, or if you attempt to create an object at compile time before the class is complete:
eval "class Foo {"; Foo->new; # error
class Bar { BEGIN { Bar->new } }; # error
Previously perl would assert or crash. [GH #22159 <https://github.com/Perl/perl5/issues/22159>]
New Warnings
(S inplace) You had "|-" or "-|" in @ARGV and tried to use "<>" to read from it.
Previously this would fork and produce a confusing error message. [GH #21176 <https://github.com/Perl/perl5/issues/21176>]
(D deprecated::missing_import_called_with_args) You called the import() or unimport() method of a class that has no import method defined in its inheritance graph, and passed an argument to the method. This is very often the sign of a misspelled package name in a use or require statement that has silently succeeded due to a case insensitive file system.
Another common reason this may happen is when mistakenly attempting to import or unimport a symbol from a class definition or package which does not use "Exporter" or otherwise define its own "import" or "unimport" method.
This warning now honors being marked as fatal. [GH #13814 <https://github.com/Perl/perl5/issues/13814>]
There used to be several places in the perl core that would print a generic "Out of memory!" message and abort when memory allocation failed, giving no indication which program it was that ran out of memory. These have been modified to include the word "perl" and the general area of the allocation failure, e.g. "Out of memory in perl:util:safesysrealloc". [GH #21672 <https://github.com/Perl/perl5/issues/21672>]
This warning now mentions the name of the control flow operator that triggered the diagnostic (e.g. "return", "exit", "die", etc).
It also covers more cases: Previously, the warning was only triggered if a low-precedence logical operator (like "and", "or", "xor") was involved. Now it is also shown for misleading code like this:
exit $x ? 0 : 1; # actually parses as: exit($x) ? 0 : 1;
exit $x == 0; # actually parses as: exit($x) == 0;
This warning is now slightly more accurate in cases involving "length", "pop", "shift", or "splice":
my $x;
length($x) == 0
# Before:
# Use of uninitialized value $x in numeric eq (==) at ...
# Now:
# Use of uninitialized value length($x) in numeric eq (==) at ...
That is, the warning no longer implies that $x was used directly as an operand of "==", which it wasn't.
Similarly:
my @xs;
shift @xs == 0
# Before:
# Use of uninitialized value within @xs in numeric eq (==) at ...
# Now:
# Use of uninitialized value shift(@xs) in numeric eq (==) at ...
This is more accurate because there never was an "undef" within @xs as the warning implied. (The warning for "pop" works analogously.)
Finally:
my @xs = (1, 2, 3);
splice(@xs, 0, 0) == 0
# Before:
# Use of uninitialized value within @xs in numeric eq (==) at ...
# Now:
# Use of uninitialized value in numeric eq (==) at ...
That is, in cases where "splice" returns "undef", it no longer unconditionally blames its first argument. This was misleading because "splice" can return "undef" even if none of its arguments contain "undef".
[GH #21930 <https://github.com/Perl/perl5/issues/21930>]
Prevent this warning appearing spuriously when checking the heuristic for the You need to quote "%s" warning.
[GH #22145 <https://github.com/Perl/perl5/issues/22145>]
Tests were added and changed to reflect the other additions and changes in this release. Furthermore, these significant changes were made:
Also tested for is if the various locale categories can indeed be set independently to disparate locales. (An example of where you might want to do this is if you are a Western Canadian living and working in Holland. You likely will want to have the "LC_MONETARY" locale be set to where you are living, but have the other parts of your locale retain your native English values. Later, as you get a bit more comfortable with Dutch, and in order to communicate better with your colleagues, you might want to change "LC_TIME" and "LC_NUMERIC" to Dutch, while leaving "LC_CTYPE" and "LC_COLLATE" set to English indefinitely.)
Work around a bug in most 32-bit Mingw builds, where the generated code, including the code in the gcc support library, assumes 16-byte stack alignment, which 32-bit Windows does not preserve. [GH #21313 <https://github.com/Perl/perl5/issues/21313>]
Enable "copysign", "signbit", "acosh", "asinh", "atanh", "exp2", "tgamma" in the bundled configuration used for MSVC. [GH #21610 <https://github.com/Perl/perl5/issues/21610>]
The build process no longer supports Visual Studio 2013. This was failing to build at a very basic level and there have been no reports of such failures. [GH #21624 <https://github.com/Perl/perl5/issues/21624>]
Fixed compilation by defining proper value for "perl_lc_all_category_positions_init".
Increased buffer size when reading config_H.SH to fix compilation under clang.
This new build option is highly experimental and is not enabled by default. Perl can be built with it by using the Configure option "-Accflags='-DPERL_RC_STACK'".
It makes the argument stack bump the reference count of SVs pushed onto it. It is mostly functional, but currently slow and incomplete.
It is intended in the long term that this build option will become the default option, and then finally the only option; but this will be many releases away.
In particular, there is currently no support within XS code for using these new features. So under this build option, all XS functions are called via a backwards-compatibility wrapper which slows down such calls.
In future releases, better support for XS code is intended to be added. It is expected that straightforward XS code will eventually be able to make use of a reference-counted stack without modification, with any heavy lifting being handled by the XS compiler ("xsubpp") and the macros which it outputs. But code which implements PP() functions will eventually have to be modified to use a new PP API: rpp_foo() rather than PUSHs() etc. But this new API is not yet stable, nor has it yet been back-ported via "Devel::PPPort".
See perlguts for more details.
Beware if you use this flag in XS code: your evaluated code will need to support whatever strictness or features are in effect at the point your XS function is called.
[GH #21415 <https://github.com/Perl/perl5/issues/21415>]
perl's -X flag disables all warnings globally, but «use 5.036» didn't respect that until now. [GH #21431 <https://github.com/Perl/perl5/issues/21431>]
This incidentally fixed a TODO test for "B::Deparse". [GH #19370 <https://github.com/Perl/perl5/pull/19370>]
To enable this add "-Accflags=-DPERL_STACK_OFFSET_SSIZET" or equivalent to the "Configure" command-line.
[GH #20917 <https://github.com/Perl/perl5/issues/20917>] [GH #21523 <https://github.com/Perl/perl5/issues/21523>]
However, testing has shown that Darwin's implementation of thread-safe locale handling has bugs. So now Perl doesn't attempt to use the thread-safe operations when compiled on Darwin.
As before, you can check to see if your program is running with thread-safe locales by checking if the value of "${^SAFE_LOCALES}" is 1.
[GH #21534 <https://github.com/Perl/perl5/issues/21534>]
use v5.36.0;
sub outer($oc) {
my sub inner ($c) {
outer($c-1) if $c; # Can't undef active subroutine
}
inner($oc);
}
outer(2);
[GH #18606 <https://github.com/Perl/perl5/issues/18606>]
use v5.36.0;
sub outer ($x) {
my sub inner ($label) {
say "$label $x";
}
inner("first");
outer("inner") if $x eq "outer";
# this call to inner() sees the wrong $x
inner("second");
}
outer("outer");
[GH #21987 <https://github.com/Perl/perl5/issues/21987>]
The "streamzip" utility does not get installed on Windows but should get installed.
Perl 5.40.0 represents approximately 11 months of development since Perl 5.38.0 and contains approximately 160,000 lines of changes across 1,500 files from 75 authors.
Excluding auto-generated files, documentation and release tools, there were approximately 110,000 lines of changes to 1,200 .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 5.40.0:
Abe Timmerman, Alexander Kanavin, Amory Meltzer, Aristotle Pagaltzis, Arne Johannessen, Beckett Normington, Bernard Quatermass, Bernd, Bruno Meneguele, Chad Granum, Chris 'BinGOs' Williams, Christoph Lamprecht, Craig A. Berry, Dagfinn Ilmari Mannsåker, Dan Book, Dan Church, Daniel Böhmer, Dan Jacobson, Dan Kogai, David Golden, David Mitchell, E. Choroba, Elvin Aslanov, Erik Huelsmann, Eugen Konkov, Gianni Ceccarelli, Graham Knop, Greg Kennedy, guoguangwu, Hauke D, H.Merijn Brand, Hugo van der Sanden, iabyn, Jake Hamby, Jakub Wilk, James E Keenan, James Raspass, Joe McMahon, Johan Vromans, John Karr, Karen Etheridge, Karl Williamson, Leon Timmermans, Lukas Mai, Marco Fontani, Marek Rouchal, Martijn Lievaart, Mathias Kende, Matthew Horsfall, Max Maischein, Nicolas Mendoza, Nicolas R, OpossumPetya, Paul Evans, Paul Marquess, Peter John Acklam, Philippe Bruhat (BooK), Raul E Rangel, Renee Baecker, Ricardo Signes, Richard Leach, Scott Baker, Sevan Janiyan, Sisyphus, Steve Hay, TAKAI Kousuke, Todd Rinaldo, Tomasz Konojacki, Tom Hughes, Tony Cook, William Lyu, x-yuri, Yves Orton, Zakariyya Mughal, Дилян Палаузов.
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.
If you find what you think is a bug, you might check the perl bug database at <https://github.com/Perl/perl5/issues>. There may also be information at <https://www.perl.org/>, the Perl Home Page.
If you believe you have an unreported bug, please open an issue at <https://github.com/Perl/perl5/issues>. Be sure to trim your bug down to a tiny but sufficient test case.
If the bug you are reporting has security implications which make it inappropriate to send to a public issue tracker, then see "SECURITY VULNERABILITY CONTACT INFORMATION" in perlsec for details of how to report the issue.
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.
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.
| 2024-06-09 | perl v5.40.0 |