PERL5360DELTA(1) Perl Programmers Reference Guide PERL5360DELTA(1)
NAME
perl5360delta - what is new for perl v5.36.0
DESCRIPTION
This document describes differences between the 5.34.0 release and the
5.36.0 release.
Core Enhancements
"use v5.36"
As always, "use v5.36" turns on the feature bundle for that version of
Perl.
The 5.36 bundle enables the "signatures" feature. Introduced in Perl
version 5.20.0, and modified several times since, the subroutine
signatures feature is now no longer considered experimental. It is now
considered a stable language feature and no longer prints a warning.
use v5.36;
sub add ($x, $y) {
return $x + $y;
}
Despite this, certain elements of signatured subroutines remain
experimental; see below.
The 5.36 bundle enables the "isa" feature. Introduced in Perl version
5.32.0, this operator has remained unchanged since then. The operator is
now considered a stable language feature. For more detail see "Class
Instance Operator" in perlop.
The 5.36 bundle also disables the features "indirect", and
"multidimensional". These will forbid, respectively: the use of
"indirect" method calls (like "$x = new Class;"); the use of a list
expression as a hash key to simulate sparse multidimensional arrays.
The specifics of these changes can be found in feature, but the short
version is: this is a bit like having more "use strict" turned on,
disabling features that cause more trouble than they're worth.
Furthermore, "use v5.36" will also enable warnings as if you'd written
"use warnings".
Finally, with this release, the experimental "switch" feature, present
in every feature bundle since they were introduced in v5.10, has been
removed from the v5.36 bundle. If you want to use it (against our
advice), you'll have to enable it explicitly.
-g command-line flag
A new command-line flag, -g, is available. It is a simpler alias for
-0777.
For more information, see "-g" in perlrun.
Unicode 14.0 is supported
See <https://www.unicode.org/versions/Unicode14.0.0/> for details.
regex sets are no longer considered experimental
Prior to this release, the regex sets feature (officially named
"Extended Bracketed Character Classes") was considered experimental.
Introduced in Perl version 5.18.0, and modified several times since,
this is now considered a stable language feature and its use no longer
prints a warning. See "Extended Bracketed Character Classes" in
perlrecharclass.
Variable length lookbehind is mostly no longer considered experimental
Prior to this release, any form of variable length lookbehind was
considered experimental. With this release the experimental status has
been reduced to cover only lookbehind that contains capturing
parenthesis. This is because it is not clear if
"aaz"=~/(?=z)(?<=(a|aa))/
should match and leave $1 equaling "a" or "aa". Currently it will match
the longest possible alternative, "aa". While we are confident that the
overall construct will now match only when it should, we are not
confident that we will keep the current "longest match" behavior.
SIGFPE no longer deferred
Floating-point exceptions are now delivered immediately, in the same way
as other "fault"-like signals such as SIGSEGV. This means one has at
least a chance to catch such a signal with a $SIG{FPE} handler, e.g. so
that "die" can report the line in perl that triggered it.
Stable boolean tracking
The "true" and "false" boolean values, often accessed by constructions
like "!!0" and "!!1", as well as being returned from many core functions
and operators, now remember their boolean nature even through assignment
into variables. The new function is_bool() in builtin can check whether
a value has boolean nature.
This is likely to be useful when interoperating with other languages or
data-type serialisation, among other places.
iterating over multiple values at a time (experimental)
You can now iterate over multiple values at a time by specifying a list
of lexicals within parentheses. For example,
for my ($key, $value) (%hash) { ... }
for my ($left, $right, $gripping) (@moties) { ... }
Prior to perl v5.36, attempting to specify a list after "for my" was a
syntax error.
This feature is currently experimental and will cause a warning of
category "experimental::for_list". For more detail see "Compound
Statements" in perlsyn. See also "builtin::indexed" in this document,
which is a handy companion to n-at-a-time foreach.
builtin functions (experimental)
A new core module builtin has been added, which provides documentation
for new always-present functions that are built into the interpreter.
say "Reference type of arrays is ", builtin::reftype([]);
It also provides a lexical import mechanism for providing short name
versions of these functions.
use builtin 'reftype';
say "Reference type of arrays is ", reftype([]);
This builtin function mechanism and the functions it provides are all
currently experimental. We expect that "builtin" itself will cease to
be experimental in the near future, but that individual functions in it
may become stable on an ongoing basis. Other functions will be added to
"builtin" over time.
For details, see builtin, but here's a summary of builtin functions in
v5.36:
builtin::trim
This function treats its argument as a string, returning the result
of removing all white space at its beginning and ending.
builtin::indexed
This function returns a list twice as big as its argument list,
where each item is preceded by its index within that list. This is
primarily useful for using the new "foreach" syntax with multiple
iterator variables to iterate over an array or list, while also
tracking the index of each item:
use builtin 'indexed';
foreach my ($index, $val) (indexed @array) {
...
}
builtin::true, builtin::false, builtin::is_bool
"true" and "false" return boolean true and false values. Perl is
still perl, and doesn't have strict typing of booleans, but these
values will be known to have been created as booleans. "is_bool"
will tell you whether a value was known to have been created as a
boolean.
builtin::weaken, builtin::unweaken, builtin::is_weak
These functions will, respectively: weaken a reference; strengthen a
reference; and return whether a reference is weak. (A weak
reference is not counted for garbage collection purposes. See
perlref.) These can take the place of some similar routines in
Scalar::Util.
builtin::blessed, builtin::refaddr, builtin::reftype
These functions provide more data about references (or non-
references, actually!) and can take the place of similar routines
found in Scalar::Util.
builtin::ceil, builtin::floor
"ceil" returns the smallest integer greater than or equal to its
argument. "floor" returns the largest integer less than or equal to
its argument. These can take the place of similar routines found in
POSIX.
"defer" blocks (experimental)
This release adds support for "defer" blocks, which are blocks of code
prefixed by the "defer" modifier. They provide a section of code which
runs at a later time, during scope exit.
In brief, when a "defer" block is reached at runtime, its body is set
aside to be run when the enclosing scope is exited. It is unlike a
UNITCHECK (among other reasons) in that if the block containing the
"defer" block is exited before the block is reached, it will not be run.
"defer" blocks can be used to take the place of "scope guard" objects
where an object is passed a code block to be run by its destructor.
For more information, see "defer blocks" in perlsyn.
try/catch can now have a "finally" block (experimental)
The experimental "try"/"catch" syntax has been extended to support an
optional third block introduced by the "finally" keyword.
try {
attempt();
print "Success\n";
}
catch ($e) {
print "Failure\n";
}
finally {
print "This happens regardless\n";
}
This provides code which runs at the end of the "try"/"catch" construct,
even if aborted by an exception or control-flow keyword. They are
similar to "defer" blocks.
For more information, see "Try Catch Exception Handling" in perlsyn.
non-ASCII delimiters for quote-like operators (experimental)
Perl traditionally has allowed just four pairs of string/pattern
delimiters: "( )" "{ }" "[ ]" and "< >", all in the ASCII range.
Unicode has hundreds more possibilities, and using this feature enables
many of them. When enabled, you can say "qr« »" for example, or
"use utf8; q𝄃string𝄂". See "The 'extra_paired_delimiters' feature" in
feature for details.
@_ is now experimental within signatured subs
Even though subroutine signatures are now stable, use of the legacy
arguments array (@_) with a subroutine that has a signature remains
experimental, with its own warning category. Silencing the
"experimental::signatures" warning category is not sufficient to dismiss
this. The new warning is emitted with the category name
"experimental::args_array_with_signatures".
Any subroutine that has a signature and tries to make use of the
defaults argument array or an element thereof (@_ or $_[INDEX]), either
explicitly or implicitly (such as "shift" or "pop" with no argument)
will provoke a warning at compile-time:
use v5.36;
sub f ($x, $y = 123) {
say "The first argument is $_[0]";
}
Use of @_ in array element with signatured subroutine is experimental
at file.pl line 4.
The behaviour of code which attempts to do this is no longer specified,
and may be subject to change in a future version.
Incompatible Changes
A physically empty sort is now a compile-time error
@a = sort @empty; # unaffected
@a = sort; # now a compile-time error
@a = sort (); # also a compile-time error
A bare sort used to be a weird way to create an empty list; now it
croaks at compile time. This change is intended to free up some of the
syntax space for possible future enhancements to "sort".
Deprecations
"use VERSION" (where VERSION is below v5.11) after "use v5.11" is deprecated
When in the scope of "use v5.11" or later, a "use vX" line where X is
lower than v5.11 will now issue a warning:
Downgrading a use VERSION declaration to below v5.11 is deprecated
For example:
use v5.14;
say "The say statement is permitted";
use v5.8; # This will print a warning
print "We must use print\n";
This is because the Perl team plans to change the behavior in this case.
Since Perl v5.12 (and parts of v5.11), strict is enabled unless it had
previously been disabled. In other words:
no strict;
use v5.12; # will not enable strict, because "no strict" preceded it
$x = 1; # permitted, despite no "my" declaration
In the future, this behavior will be eliminated and "use VERSION" will
always enable strict for versions v5.12 and later.
Code which wishes to mix versions in this manner should use lexical
scoping with block syntax to ensure that the differently versioned
regions remain lexically isolated.
{
use v5.14;
say "The say statement is permitted";
}
{
use v5.8; # No warning is emitted
print "We must use print\n";
}
Of course, this is probably not something you ever need to do! If the
first block compiles, it means you're using perl v5.14.0 or later.
Performance Enhancements
• We now probe for compiler support for C11 thread local storage, and
where available use this for "implicit context" for XS extensions
making API calls for a threaded Perl build. This requires fewer
function calls at the C level than POSIX thread specific storage. We
continue to use the pthreads approach if the C11 approach is not
available.
Configure run with the defaults will build an unthreaded Perl (which
is slightly faster), but most operating systems ship a threaded
Perl.
• Perl can now be configured to no longer allocate keys for large
hashes from the shared string table.
The same internal datatype ("PVHV") is used for all of
• Symbol tables
• Objects (by default)
• Associative arrays
The shared string table was originally added to improve performance
for blessed hashes used as objects, because every object instance
has the same keys, so it is an optimisation to share memory between
them. It also makes sense for symbol tables, where derived classes
will have the same keys (typically method names), and the OP trees
built for method calls can also share memory. The shared string
table behaves roughly like a cache for hash keys.
But for hashes actually used as associative arrays - mapping keys to
values - typically the keys are not re-used in other hashes. For
example, "seen" hashes are keyed by object IDs (or addresses), and
logically these keys won't repeat in other hashes.
Storing these "used just once" keys in the shared string table
increases CPU and RAM use for no gain. For such keys the shared
string table behaves as a cache with a 0% hit rate. Storing all the
keys there increases the total size of the shared string table, as
well as increasing the number of times it is resized as it grows.
Worse - in any environment that has "copy on write" memory for child
process (such as a pre-forking server), the memory pages used for
the shared string table rapidly need to be copied as the child
process manipulates hashes. Hence if most of the shared string table
is such that keys are used only in one place, there is no benefit
from re-use within the perl interpreter, but a high cost due to more
pages for the OS to copy.
The perl interpreter can now be Configured to disable shared hash
keys for "large" hashes (that are neither objects nor symbol
tables). To do so, add
"-Accflags='-DPERL_USE_UNSHARED_KEYS_IN_LARGE_HASHES'" to your
Configure options. "Large" is a heuristic -- currently the
heuristic is that sharing is disabled when adding a key to a hash
triggers allocation of more storage, and the hash has more than 42
keys.
This might cause slightly increased memory usage for programs that
create (unblessed) data structures that contain multiple large
hashes that share the same keys. But generally our testing suggests
that for the specific cases described it is a win, and other code is
unaffected.
• In certain scenarios, creation of new scalars is now noticeably
faster.
For example, the following code is now executing ~30% faster:
$str = "A" x 64;
for (0..1_000_000) {
@svs = split //, $str
}
(You can read more about this one in [perl #19414]
<https://github.com/Perl/perl5/pull/19414>.)
Modules and Pragmata
Updated Modules and Pragmata
• Archive::Tar has been upgraded from version 2.38 to 2.40.
• Attribute::Handlers has been upgraded from version 1.01 to 1.02.
• attributes has been upgraded from version 0.33 to 0.34.
• B has been upgraded from version 1.82 to 1.83.
• B::Concise has been upgraded from version 1.004 to 1.006.
• B::Deparse has been upgraded from version 1.56 to 1.64.
• bignum has been upgraded from version 0.51 to 0.65.
• charnames has been upgraded from version 1.48 to 1.50.
• Compress::Raw::Bzip2 has been upgraded from version 2.101 to 2.103.
• Compress::Raw::Zlib has been upgraded from version 2.101 to 2.105.
• CPAN has been upgraded from version 2.28 to 2.33.
• Data::Dumper has been upgraded from version 2.179 to 2.184.
• DB_File has been upgraded from version 1.855 to 1.857.
• Devel::Peek has been upgraded from version 1.30 to 1.32.
• Devel::PPPort has been upgraded from version 3.62 to 3.68.
• diagnostics has been upgraded from version 1.37 to 1.39.
• Digest has been upgraded from version 1.19 to 1.20.
• DynaLoader has been upgraded from version 1.50 to 1.52.
• Encode has been upgraded from version 3.08 to 3.17.
• Errno has been upgraded from version 1.33 to 1.36.
• experimental has been upgraded from version 0.024 to 0.028.
• Exporter has been upgraded from version 5.76 to 5.77.
• ExtUtils::MakeMaker has been upgraded from version 7.62 to 7.64.
• ExtUtils::Miniperl has been upgraded from version 1.10 to 1.11.
• ExtUtils::ParseXS has been upgraded from version 3.43 to 3.45.
• ExtUtils::Typemaps has been upgraded from version 3.43 to 3.45.
• Fcntl has been upgraded from version 1.14 to 1.15.
• feature has been upgraded from version 1.64 to 1.72.
• File::Compare has been upgraded from version 1.1006 to 1.1007.
• File::Copy has been upgraded from version 2.35 to 2.39.
• File::Fetch has been upgraded from version 1.00 to 1.04.
• File::Find has been upgraded from version 1.39 to 1.40.
• File::Glob has been upgraded from version 1.33 to 1.37.
• File::Spec has been upgraded from version 3.80 to 3.84.
• File::stat has been upgraded from version 1.09 to 1.12.
• FindBin has been upgraded from version 1.52 to 1.53.
• GDBM_File has been upgraded from version 1.19 to 1.23.
• Hash::Util has been upgraded from version 0.25 to 0.28.
• Hash::Util::FieldHash has been upgraded from version 1.21 to 1.26.
• HTTP::Tiny has been upgraded from version 0.076 to 0.080.
• I18N::Langinfo has been upgraded from version 0.19 to 0.21.
• if has been upgraded from version 0.0609 to 0.0610.
• IO has been upgraded from version 1.46 to 1.50.
• IO-Compress has been upgraded from version 2.102 to 2.106.
• IPC::Open3 has been upgraded from version 1.21 to 1.22.
• JSON::PP has been upgraded from version 4.06 to 4.07.
• libnet has been upgraded from version 3.13 to 3.14.
• Locale::Maketext has been upgraded from version 1.29 to 1.31.
• Math::BigInt has been upgraded from version 1.999818 to 1.999830.
• Math::BigInt::FastCalc has been upgraded from version 0.5009 to
0.5012.
• Math::BigRat has been upgraded from version 0.2614 to 0.2621.
• Module::CoreList has been upgraded from version 5.20210520 to
5.20220520.
• mro has been upgraded from version 1.25_001 to 1.26.
• NEXT has been upgraded from version 0.68 to 0.69.
• Opcode has been upgraded from version 1.50 to 1.57.
• open has been upgraded from version 1.12 to 1.13.
• overload has been upgraded from version 1.33 to 1.35.
• perlfaq has been upgraded from version 5.20210411 to 5.20210520.
• PerlIO has been upgraded from version 1.11 to 1.12.
• Pod::Functions has been upgraded from version 1.13 to 1.14.
• Pod::Html has been upgraded from version 1.27 to 1.33.
• Pod::Simple has been upgraded from version 3.42 to 3.43.
• POSIX has been upgraded from version 1.97 to 2.03.
• re has been upgraded from version 0.41 to 0.43.
• Scalar::Util has been upgraded from version 1.55 to 1.62.
• sigtrap has been upgraded from version 1.09 to 1.10.
• Socket has been upgraded from version 2.031 to 2.033.
• sort has been upgraded from version 2.04 to 2.05.
• Storable has been upgraded from version 3.23 to 3.26.
• Sys::Hostname has been upgraded from version 1.23 to 1.24.
• Test::Harness has been upgraded from version 3.43 to 3.44.
• Test::Simple has been upgraded from version 1.302183 to 1.302190.
• Text::ParseWords has been upgraded from version 3.30 to 3.31.
• Text::Tabs has been upgraded from version 2013.0523 to 2021.0814.
• Text::Wrap has been upgraded from version 2013.0523 to 2021.0814.
• threads has been upgraded from version 2.26 to 2.27.
• threads::shared has been upgraded from version 1.62 to 1.64.
• Tie::Handle has been upgraded from version 4.2 to 4.3.
• Tie::Hash has been upgraded from version 1.05 to 1.06.
• Tie::Scalar has been upgraded from version 1.05 to 1.06.
• Tie::SubstrHash has been upgraded from version 1.00 to 1.01.
• Time::HiRes has been upgraded from version 1.9767 to 1.9770.
• Unicode::Collate has been upgraded from version 1.29 to 1.31.
• Unicode::Normalize has been upgraded from version 1.28 to 1.31.
• Unicode::UCD has been upgraded from version 0.75 to 0.78.
• UNIVERSAL has been upgraded from version 1.13 to 1.14.
• version has been upgraded from version 0.9928 to 0.9929.
• VMS::Filespec has been upgraded from version 1.12 to 1.13.
• VMS::Stdio has been upgraded from version 2.45 to 2.46.
• warnings has been upgraded from version 1.51 to 1.58.
• Win32 has been upgraded from version 0.57 to 0.59.
• XS::APItest has been upgraded from version 1.16 to 1.22.
• XS::Typemap has been upgraded from version 0.18 to 0.19.
• XSLoader has been upgraded from version 0.30 to 0.31.
Documentation
New Documentation
Porting/vote_admin_guide.pod
This document provides the process for administering an election or vote
within the Perl Core Team.
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, open an issue
at <https://github.com/Perl/perl5/issues>.
Additionally, the following selected changes have been made:
perlapi
• This has been cleaned up some, and more than 80% of the (previously
many) undocumented functions have now either been documented or
deemed to have been inappropriately marked as API.
As always, Patches Welcome!
perldeprecation
• notes the new location for functions moved from Pod::Html to
Pod::Html::Util that are no longer intended to be used outside of
core.
perlexperiment
• notes the ":win32" IO pseudolayer is removed (this happened in
5.35.2).
perlgov
• The election process has been finetuned to allow the vote to be
skipped if there are no more candidates than open seats.
• A special election is now allowed to be postponed for up to twelve
weeks, for example until a normal election.
perlop
• now notes that an invocant only needs to be an object or class name
for method calls, not for subroutine references.
perlre
• Updated to discourage the use of the /d regexp modifier.
perlrun
• -? is now a synonym for -h
• -g is now a synonym for -0777
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
• Can't "%s" out of a "defer" block
(F) An attempt was made to jump out of the scope of a defer block by
using a control-flow statement such as "return", "goto" or a loop
control. This is not permitted.
• Can't modify %s in %s (for scalar assignment to "undef")
Attempting to perform a scalar assignment to "undef", for example
via "undef = $foo;", previously triggered a fatal runtime error with
the message "Modification of a read-only value attempted." It is
more helpful to detect such attempted assignments prior to runtime,
so they are now compile time errors, resulting in the message "Can't
modify undef operator in scalar assignment".
• panic: newFORLOOP, %s
The parser failed an internal consistency check while trying to
parse a "foreach" loop.
New Warnings
• Built-in function '%s' is experimental
A call is being made to a function in the "builtin::" namespace,
which is currently experimental.
• defer is experimental
The "defer" block modifier is experimental. If you want to use the
feature, disable the warning with "no warnings
'experimental::defer'", but know that in doing so you are taking the
risk that your code may break in a future Perl version.
• Downgrading a use VERSION declaration to below v5.11 is deprecated
This warning is emitted on a "use VERSION" statement that requests a
version below v5.11 (when the effects of "use strict" would be
disabled), after a previous declaration of one having a larger
number (which would have enabled these effects)
• for my (...) is experimental
This warning is emitted if you use "for" to iterate multiple values
at a time. This syntax is currently experimental and its behaviour
may change in future releases of Perl.
• Implicit use of @_ in %s with signatured subroutine is experimental
An expression that implicitly involves the @_ arguments array was
found in a subroutine that uses a signature.
• Use of @_ in %s with signatured subroutine is experimental
An expression involving the @_ arguments array was found in a
subroutine that uses a signature.
• Wide character in $0
Attempts to put wide characters into the program name ($0) now
provoke this warning.
Changes to Existing Diagnostics
• '/' does not take a repeat count in %s
This warning used to not include the "in %s".
• Subroutine %s redefined
Localized subroutine redefinitions no longer trigger this warning.
• unexpected constant lvalue entersub entry via type/targ %d:%d" now
has a panic prefix
This makes it consistent with other checks of internal consistency
when compiling a subroutine.
• Useless use of sort in scalar context is now in the new "scalar"
category.
When "sort" is used in scalar context, it provokes a warning that
doing this is not useful. This warning used to be in the "void"
category. A new category for warnings about scalar context has now
been added, called "scalar".
• Removed a number of diagnostics
Many diagnostics that have been removed from the perl core across
many years have now also been removed from the documentation.
Configuration and Compilation
• The Perl C source code now uses some C99 features, which we have
verified are supported by all compilers we target. This means that
Perl's headers now contain some code that is legal in C99 but not
C89.
This may cause problems for some XS modules that unconditionally add
"-Werror=declaration-after-statement" to their C compiler flags if
compiling with gcc or clang. Earlier versions of Perl support long
obsolete compilers that are strict in rejecting certain C99
features, particularly mixed declarations and code, and hence it
makes sense for XS module authors to audit that their code does not
violate this. However, doing this is now only possible on these
earlier versions of Perl, hence these modules need to be changed to
only add this flag for "$] < 5.035005".
• The makedepend step is now run in parallel by using make
When using MAKEFLAGS=-j8, this significantly reduces the time
required for:
sh ./makedepend MAKE=make cflags
• Configure now tests whether "#include <xlocale.h>" is required to
use the POSIX 1003 thread-safe locale functions or some related
extensions. This prevents problems where a non-public xlocale.h is
removed in a library update, or xlocale.h isn't intended for public
use. (github #18936 <https://github.com/Perl/perl5/pull/18936>)
Testing
Tests were added and changed to reflect the other additions and changes
in this release.
Platform Support
Windows
• Support for old MSVC++ (pre-VC12) has been removed
These did not support C99 and hence can no longer be used to compile
perl.
• Support for compiling perl on Windows using Microsoft Visual Studio
2022 (containing Visual C++ 14.3) has been added.
• The :win32 IO layer has been removed. This experimental replacement
for the :unix layer never reached maturity in its nearly two decades
of existence.
VMS
"keys %ENV" on VMS returns consistent results
On VMS entries in the %ENV hash are loaded from the OS environment
on first access, hence the first iteration of %ENV requires the
entire environment to be scanned to find all possible keys. This
initialisation had always been done correctly for full iteration,
but previously was not happening for %ENV in scalar context, meaning
that "scalar %ENV" would return 0 if called before any other %ENV
access, or would only return the count of keys accessed if there had
been no iteration.
These bugs are now fixed - %ENV and "keys %ENV" in scalar context
now return the correct result - the count of all keys in the
environment.
Discontinued Platforms
AT&T UWIN
UWIN is a UNIX compatibility layer for Windows. It was last
released in 2012 and has been superseded by Cygwin these days.
DOS/DJGPP
DJGPP is a port of the GNU toolchain to 32-bit x86 systems running
DOS. The last known attempt to build Perl on it was on 5.20, which
only got as far as building miniperl.
NetWare
Support code for Novell NetWare has been removed. NetWare was a
server operating system by Novell. The port was last updated in
July 2002, and the platform itself in May 2009.
Unrelated changes accidentally broke the build for the NetWare port
in September 2009, and in 12 years no-one has reported this.
Platform-Specific Notes
z/OS
This update enables us to build EBCDIC static/dynamic and
31-bit/64-bit addressing mode Perl. The number of tests that pass is
consistent with the baseline before these updates.
These changes also provide the base support to be able to provide
ASCII static/dynamic and 31-bit/64-bit addressing mode Perl.
The z/OS (previously called OS/390) README was updated to describe
ASCII and EBCDIC builds.
Internal Changes
• Since the removal of PERL_OBJECT in Perl 5.8, PERL_IMPLICIT_CONTEXT
and MULTIPLICITY have been synonymous and they were being used
interchangeably. To simplify the code, all instances of
PERL_IMPLICIT_CONTEXT have been replaced with MULTIPLICITY.
PERL_IMPLICIT_CONTEXT will remain defined for compatibility with XS
modules.
• The API constant formerly named "G_ARRAY", indicating list context,
has now been renamed to a more accurate "G_LIST". A compatibilty
macro "G_ARRAY" has been added to allow existing code to work
unaffected. New code should be written using the new constant
instead. This is supported by "Devel::PPPort" version 3.63.
• Macros have been added to perl.h to facilitate version comparisons:
"PERL_GCC_VERSION_GE", "PERL_GCC_VERSION_GT", "PERL_GCC_VERSION_LE"
and "PERL_GCC_VERSION_LT".
Inline functions have been added to embed.h to determine the
position of the least significant 1 bit in a word: "lsbit_pos32" and
"lsbit_pos64".
• "Perl_ptr_table_clear" has been deleted. This has been marked as
deprecated since v5.14.0 (released in 2011), and is not used by any
code on CPAN.
• Added new boolean macros and functions. See "Stable boolean
tracking" for related information and perlapi for documentation.
• sv_setbool
• sv_setbool_mg
• SvIsBOOL
• Added 4 missing functions for dealing with RVs:
• sv_setrv_noinc
• sv_setrv_noinc_mg
• sv_setrv_inc
• sv_setrv_inc_mg
• xs_handshake()'s two failure modes now provide distinct messages.
• Memory for hash iterator state ("struct xpvhv_aux") is now allocated
as part of the hash body, instead of as part of the block of memory
allocated for the main hash array.
• A new phase_name() interface provides access to the name for each
interpreter phase (i.e., PL_phase value).
• The "pack" behavior of "U" has changed for EBCDIC.
• New equality-test functions "sv_numeq" and "sv_streq" have been
added, along with "..._flags"-suffixed variants. These expose a
simple and consistent API to perform numerical or string comparison
which is aware of operator overloading.
• Reading the string form of an integer value no longer sets the flag
"SVf_POK". The string form is still cached internally, and still
re-read directly by the macros SvPV(sv) etc (inline, without calling
a C function). XS code that already calls the APIs to get values
will not be affected by this change. XS code that accesses flags
directly instead of using API calls to express its intent might
break, but such code likely is already buggy if passed some other
values, such as floating point values or objects with string
overloading.
This small change permits code (such as JSON serializers) to
reliably determine between
• a value that was initially written as an integer, but then read
as a string
my $answer = 42;
print "The answer is $answer\n";
• that same value that was initially written as a string, but then
read as an integer
my $answer = "42";
print "That doesn't look right\n"
unless $answer == 6 * 9;
For the first case (originally written as an integer), we now have:
use Devel::Peek;
my $answer = 42;
Dump ($answer);
my $void = "$answer";
print STDERR "\n";
Dump($answer)
SV = IV(0x562538925778) at 0x562538925788
REFCNT = 1
FLAGS = (IOK,pIOK)
IV = 42
SV = PVIV(0x5625389263c0) at 0x562538925788
REFCNT = 1
FLAGS = (IOK,pIOK,pPOK)
IV = 42
PV = 0x562538919b50 "42"\0
CUR = 2
LEN = 10
For the second (originally written as a string), we now have:
use Devel::Peek;
my $answer = "42";
Dump ($answer);
my $void = $answer == 6 * 9;
print STDERR "\n";
Dump($answer)'
SV = PV(0x5586ffe9bfb0) at 0x5586ffec0788
REFCNT = 1
FLAGS = (POK,IsCOW,pPOK)
PV = 0x5586ffee7fd0 "42"\0
CUR = 2
LEN = 10
COW_REFCNT = 1
SV = PVIV(0x5586ffec13c0) at 0x5586ffec0788
REFCNT = 1
FLAGS = (IOK,POK,IsCOW,pIOK,pPOK)
IV = 42
PV = 0x5586ffee7fd0 "42"\0
CUR = 2
LEN = 10
COW_REFCNT = 1
(One can't rely on the presence or absence of the flag "SVf_IsCOW"
to determine the history of operations on a scalar.)
Previously both cases would be indistinguishable, with all 4 flags
set:
SV = PVIV(0x55d4d62edaf0) at 0x55d4d62f0930
REFCNT = 1
FLAGS = (IOK,POK,pIOK,pPOK)
IV = 42
PV = 0x55d4d62e1740 "42"\0
CUR = 2
LEN = 10
(and possibly "SVf_IsCOW", but not always)
This now means that if XS code really needs to determine which form
a value was first written as, it should implement logic roughly
if (flags & SVf_IOK|SVf_NOK) && !(flags & SVf_POK)
serialize as number
else if (flags & SVf_POK)
serialize as string
else
the existing guesswork ...
Note that this doesn't cover "dualvars" - scalars that report
different values when asked for their string form or number form
(such as $!). Most serialization formats cannot represent such
duplicity.
The existing guesswork remains because as well as dualvars, values
might be "undef", references, overloaded references, typeglobs and
other things that Perl itself can represent but do not map one-to-
one into external formats, so need some amount of approximation or
encapsulation.
• "sv_dump" (and Devel::Peek’s "Dump" function) now escapes high-bit
octets in the PV as hex rather than octal. Since most folks
understand hex more readily than octal, this should make these dumps
a bit more legible. This does not affect any other diagnostic
interfaces like "pv_display".
Selected Bug Fixes
• utime() now correctly sets errno/$! when called on a closed handle.
• The flags on the OPTVAL parameter to setsockopt() were previously
checked before magic was called, possibly treating a numeric value
as a packed buffer or vice versa. It also ignored the UTF-8 flag,
potentially treating the internal representation of an upgraded SV
as the bytes to supply to the setsockopt() system call. (github
#18660 <https://github.com/Perl/perl5/issues/18660>)
• Only set IOKp, not IOK on $) and $(. This was issue #18955
<https://github.com/Perl/perl5/issues/18955>: This will prevent
serializers from serializing these variables as numbers (which loses
the additional groups). This restores behaviour from 5.16
• Use of the "mktables" debugging facility would cause perl to croak
since v5.31.10; this problem has now been fixed.
• "makedepend" logic is now compatible with BSD make (fixes GH #19046
<https://github.com/Perl/perl5/issues/19046>).
• Calling "untie" on a tied hash that is partway through iteration now
frees the iteration state immediately.
Iterating a tied hash causes perl to store a copy of the current
hash key to track the iteration state, with this stored copy passed
as the second parameter to "NEXTKEY". This internal state is freed
immediately when tie hash iteration completes, or if the hash is
destroyed, but due to an implementation oversight, it was not freed
if the hash was untied. In that case, the internal copy of the key
would persist until the earliest of
1. "tie" was called again on the same hash
2. The (now untied) hash was iterated (ie passed to any of "keys",
"values" or "each")
3. The hash was destroyed.
This inconsistency is now fixed - the internal state is now freed
immediately by "untie".
As the precise timing of this behaviour can be observed with pure
Perl code (the timing of "DESTROY" on objects returned from
"FIRSTKEY" and "NEXTKEY") it's just possible that some code is
sensitive to it.
• The Internals::getcwd() function added for bootstrapping miniperl in
perl 5.30.0 is now only available in miniperl. [github #19122]
• Setting a breakpoint on a BEGIN or equivalently a "use" statement
could cause a memory write to a freed "dbstate" op. [GH #19198
<https://github.com/Perl/perl5/issues/19198>]
• When bareword filehandles are disabled, the parser was interpreting
any bareword as a filehandle, even when immediatey followed by
parens.
Errata From Previous Releases
• perl5300delta mistakenly identified a CVE whose correct
identification is CVE-2015-1592.
Obituaries
Raun "Spider" Boardman (SPIDB on CPAN), author of at least 66 commits to
the Perl 5 core distribution between 1996 and 2002, passed away May 24,
2021 from complications of COVID. He will be missed.
David H. Adler (DHA) passed away on November 16, 2021. In 1997, David
co-founded NY.pm, the first Perl user group, and in 1998 co-founded Perl
Mongers to help establish other user groups across the globe. He was a
frequent attendee at Perl conferences in both North America and Europe
and well known for his role in organizing Bad Movie Night celebrations
at those conferences. He also contributed to the work of the Perl
Foundation, including administering the White Camel awards for community
service. He will be missed.
Acknowledgements
Perl 5.36.0 represents approximately a year of development since Perl
5.34.0 and contains approximately 250,000 lines of changes across 2,000
files from 82 authors.
Excluding auto-generated files, documentation and release tools, there
were approximately 190,000 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 5.36.0:
Alyssa Ross, Andrew Fresh, Aristotle Pagaltzis, Asher Mancinelli,
Atsushi Sugawara, Ben Cornett, Bernd, Biswapriyo Nath, Brad Barden,
Bram, Branislav Zahradník, brian d foy, Chad Granum, Chris 'BinGOs'
Williams, Christian Walde (Mithaldu), Christopher Yeleighton, Craig A.
Berry, cuishuang, Curtis Poe, Dagfinn Ilmari Mannsåker, Dan Book, Daniel
Laügt, Dan Jacobson, Dan Kogai, Dave Cross, Dave Lambley, David
Cantrell, David Golden, David Marshall, David Mitchell, E. Choroba,
Eugen Konkov, Felipe Gasper, François Perrad, Graham Knop, H.Merijn
Brand, Hugo van der Sanden, Ilya Sashcheka, Ivan Panchenko, Jakub Wilk,
James E Keenan, James Raspass, Karen Etheridge, Karl Williamson, Leam
Hall, Leon Timmermans, Magnus Woldrich, Matthew Horsfall, Max Maischein,
Michael G Schwern, Michiel Beijen, Mike Fulton, Neil Bowers, Nicholas
Clark, Nicolas R, Niyas Sait, Olaf Alders, Paul Evans, Paul Marquess,
Petar-Kaleychev, Pete Houston, Renee Baecker, Ricardo Signes, Richard
Leach, Robert Rothenberg, Sawyer X, Scott Baker, Sergey Poznyakoff,
Sergey Zhmylove, Sisyphus, Slaven Rezic, Steve Hay, Sven Kirmess, TAKAI
Kousuke, Thibault Duponchelle, Todd Rinaldo, Tomasz Konojacki, Tomoyuki
Sadahiro, Tony Cook, Unicode Consortium, Yves Orton, Михаил Козачков.
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://github.com/Perl/perl5/issues>. There may also be
information at <http://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.
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.
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