[p5sagit/p5-mst-13.2.git] / pod / perl5131delta.pod

=encoding utf8

=head1 NAME

[ this is a template for a new perldelta file. Any text flagged as
XXX needs to be processed before release. ]

perldelta - what is new for perl v5.13.1

=head1 DESCRIPTION

This document describes differences between the 5.13.0 release and
the 5.13.1 release.

If you are upgrading from an earlier release such as 5.10, first read
L<perl5120delta>, which describes differences between 5.10 and
5.12.

=head1 Notice

XXX Any important notices here

=head1 Incompatible Changes

=head2 "C<\cI<X>>"

The backslash-c construct was designed as a way of specifying
non-printable characters, but there were no restrictions (on ASCII
platforms) on what the character following the C<c> could be.  Now, that
character must be one of the ASCII characters.

=head2 localised tied hashes, arrays and scalars are no longed tied

In the following:

    tie @a, ...;
    {
	local @a;
	# here, @a is a now a new, untied array
    }
    # here, @a refers again to the old, tied array

The new local array used to be made tied too, which was fairly pointless,
and has now been fixed. This fix could however potentially cause a change
in behaviour of some code.

=head1 Core Enhancements

XXX New core language features go here. Summarise user-visible core language
enhancements. Particularly prominent performance optimisations could go
here, but most should go in the L</Performance Enhancements> section.

=head2 Exception Handling Reliability

Several changes have been made to the way C<die>, C<warn>, and C<$@>
behave, in order to make them more reliable and consistent.

When an exception is thrown inside an C<eval>, the exception is no
longer at risk of being clobbered by code running during unwinding
(e.g., destructors).  Previously, the exception was written into C<$@>
early in the throwing process, and would be overwritten if C<eval> was
used internally in the destructor for an object that had to be freed
while exiting from the outer C<eval>.  Now the exception is written
into C<$@> last thing before exiting the outer C<eval>, so the code
running immediately thereafter can rely on the value in C<$@> correctly
corresponding to that C<eval>.

Likewise, a C<local $@> inside an C<eval> will no longer clobber any
exception thrown in its scope.  Previously, the restoration of C<$@> upon
unwinding would overwrite any exception being thrown.  Now the exception
gets to the C<eval> anyway.  So C<local $@> is safe inside an C<eval>,
albeit of rather limited use.

Exceptions thrown from object destructors no longer modify the C<$@>
of the surrounding context.  (If the surrounding context was exception
unwinding, this used to be another way to clobber the exception being
thrown.  Due to the above change it no longer has that significance,
but there are other situations where C<$@> is significant.)  Previously
such an exception was sometimes emitted as a warning, and then either
string-appended to the surrounding C<$@> or completely replaced the
surrounding C<$@>, depending on whether that exception and the surrounding
C<$@> were strings or objects.  Now, an exception in this situation is
always emitted as a warning, leaving the surrounding C<$@> untouched.
In addition to object destructors, this also affects any function call
performed by XS code using the C<G_KEEPERR> flag.

C<$@> is also no longer used as an internal temporary variable when
preparing to C<die>.  Previously it was internally necessary to put
any exception object (any non-string exception) into C<$@> first,
before it could be used as an exception.  (The C API still offers the
old option, so an XS module might still clobber C<$@> in the old way.)
This change together with the foregoing means that, in various places,
C<$@> may be observed to contain its previously-assigned value, rather
than having been overwritten by recent exception-related activity.

Warnings for C<warn> can now be objects, in the same way as exceptions
for C<die>.  If an object-based warning gets the default handling,
of writing to standard error, it will of course still be stringified
along the way.  But a C<$SIG{__WARN__}> handler will now receive an
object-based warning as an object, where previously it was passed the
result of stringifying the object.

=head1 New Platforms

XXX List any platforms that this version of perl compiles on, that previous
versions did not. These will either be enabled by new files in the F<hints/>
directories, or new subdirectories and F<README> files at the top level of the
source tree.

=head1 Modules and Pragmata

XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
go here.  If Module::CoreList is updated, generate an initial draft of the
following sections using F<Porting/corelist-perldelta.pl>, which prints stub
entries to STDOUT.  Results can be pasted in place of the '=head2' entries
below.  A paragraph summary for important changes should then be added by hand.
In an ideal world, dual-life modules would have a F<Changes> file that could be
cribbed.

=head2 New Modules and Pragmata

=head2 Pragmata Changes

=head2 Updated Modules

=over

=item C<B::Deparse>

A bug has been fixed when deparsing a nextstate op that has both a
change of package (relative to the previous nextstate), or a change of
C<%^H> or other state, and a label.  Previously the label was emitted
first, leading to syntactically invalid output because a label is not
permitted immediately before a package declaration, B<BEGIN> block,
or some other things.  Now the label is emitted last.

=back

=head2 Removed Modules and Pragmata

=head1 Utility Changes

XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go
here. Most of these are built within the directories F<utils> and F<x2p>.

=over 4

=item F<XXX>

XXX

=back

=head1 New Documentation

XXX Changes which create B<new> files in F<pod/> go here.

=over 4

=item L<XXX>

XXX

=back

=head1 Changes to Existing Documentation

XXX Changes which significantly change existing files in F<pod/> go here.
Any changes to F<pod/perldiag.pod> should go in L</New or Changed Diagnostics>.


=head1 Performance Enhancements

XXX Changes which enhance performance without changing behaviour go here. There
may well be none in a stable release.

=over 4

=item *

XXX

=back

=head1 Installation and Configuration Improvements

XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
go here.

=head2 Configuration improvements

XXX

=head2 Compilation improvements

XXX

=head2 Platform Specific Changes

=over 4

=item XXX-some-platform

XXX

=back

=head1 Selected Bug Fixes

XXX Important bug fixes in the core language are summarised here.
Bug fixes in files in F<ext/> and F<lib/> are best summarised in
L</Modules and Pragmata>.

=over 4

=item *

XXX

=back

=head1 New or Changed Diagnostics

XXX New or changed warnings emitted by the core's C<C> code go here.

=over 4

=item C<XXX>

XXX

=back

=head1 Changed Internals

XXX Changes which affect the interface available to C<XS> code go here.

=over 4

=item *

XXX

=back

=head1 New Tests

XXX Changes which create B<new> files in F<t/> go here. Changes to
existing files in F<t/> aren't worth summarising, although the bugs that
they represent may be.

=over 4

=item F<XXX>

XXX

=back

=head1 Known Problems

XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
tests that had to be C<TODO>ed for the release would be noted here, unless
they were specific to a particular platform (see below).

This is a list of some significant unfixed bugs, which are regressions
from either 5.XXX.XXX or 5.XXX.XXX.

=over 4

=item *

XXX

=back

=head1 Deprecations

XXX Add any new known deprecations here.

The following items are now deprecated.

=over 4

=item *

XXX

=back

=head1 Platform Specific Notes

XXX Any changes specific to a particular platform. VMS and Win32 are the usual
stars here. It's probably best to group changes under the same section layout
as the main perldelta

=head1 Obituary

XXX If any significant core contributor has died, we've added a short obituary
here.

=head1 Acknowledgements

XXX The list of people to thank goes here.


=head1 Reporting Bugs

If you find what you think is a bug, you might check the articles
recently posted to the comp.lang.perl.misc newsgroup and the perl
bug database at http://rt.perl.org/perlbug/ .  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 B<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 C<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 please send
it to perl5-security-report@perl.org. This points to a closed subscription
unarchived mailing list, which includes all the core committers, who be able
to help assess the impact of issues, figure out a resolution, and help
co-ordinate the release of patches to mitigate or fix the problem across all
platforms on which Perl is supported. Please only use this address for
security issues in the Perl core, not for modules independently
distributed on CPAN.

=head1 SEE ALSO

The F<Changes> file for an explanation of how to view exhaustive details
on what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=cut
Commit	Line	Data
d4438f94	1	=encoding utf8
	2
	3	=head1 NAME
	4
	5	[ this is a template for a new perldelta file. Any text flagged as
	6	XXX needs to be processed before release. ]
	7
	8	perldelta - what is new for perl v5.13.1
	9
	10	=head1 DESCRIPTION
	11
	12	This document describes differences between the 5.13.0 release and
	13	the 5.13.1 release.
	14
	15	If you are upgrading from an earlier release such as 5.10, first read
	16	L<perl5120delta>, which describes differences between 5.10 and
	17	5.12.
	18
	19	=head1 Notice
	20
	21	XXX Any important notices here
	22
	23	=head1 Incompatible Changes
	24
df5278db	25	=head2 "C<\cI<X>>"
d4438f94	26
df5278db	27	The backslash-c construct was designed as a way of specifying
	28	non-printable characters, but there were no restrictions (on ASCII
	29	platforms) on what the character following the C<c> could be. Now, that
	30	character must be one of the ASCII characters.
d4438f94	31
72ecaef9	32	=head2 localised tied hashes, arrays and scalars are no longed tied
	33
	34	In the following:
	35
	36	tie @a, ...;
	37	{
	38	local @a;
	39	# here, @a is a now a new, untied array
	40	}
	41	# here, @a refers again to the old, tied array
	42
	43	The new local array used to be made tied too, which was fairly pointless,
	44	and has now been fixed. This fix could however potentially cause a change
	45	in behaviour of some code.
	46
d4438f94	47	=head1 Core Enhancements
	48
	49	XXX New core language features go here. Summarise user-visible core language
	50	enhancements. Particularly prominent performance optimisations could go
	51	here, but most should go in the L</Performance Enhancements> section.
	52
9d5401ce	53	=head2 Exception Handling Reliability
	54
	55	Several changes have been made to the way C<die>, C<warn>, and C<$@>
	56	behave, in order to make them more reliable and consistent.
	57
	58	When an exception is thrown inside an C<eval>, the exception is no
	59	longer at risk of being clobbered by code running during unwinding
	60	(e.g., destructors). Previously, the exception was written into C<$@>
	61	early in the throwing process, and would be overwritten if C<eval> was
	62	used internally in the destructor for an object that had to be freed
	63	while exiting from the outer C<eval>. Now the exception is written
	64	into C<$@> last thing before exiting the outer C<eval>, so the code
	65	running immediately thereafter can rely on the value in C<$@> correctly
	66	corresponding to that C<eval>.
	67
	68	Likewise, a C<local $@> inside an C<eval> will no longer clobber any
	69	exception thrown in its scope. Previously, the restoration of C<$@> upon
	70	unwinding would overwrite any exception being thrown. Now the exception
	71	gets to the C<eval> anyway. So C<local $@> is safe inside an C<eval>,
	72	albeit of rather limited use.
	73
	74	Exceptions thrown from object destructors no longer modify the C<$@>
	75	of the surrounding context. (If the surrounding context was exception
	76	unwinding, this used to be another way to clobber the exception being
	77	thrown. Due to the above change it no longer has that significance,
	78	but there are other situations where C<$@> is significant.) Previously
	79	such an exception was sometimes emitted as a warning, and then either
	80	string-appended to the surrounding C<$@> or completely replaced the
	81	surrounding C<$@>, depending on whether that exception and the surrounding
	82	C<$@> were strings or objects. Now, an exception in this situation is
	83	always emitted as a warning, leaving the surrounding C<$@> untouched.
	84	In addition to object destructors, this also affects any function call
	85	performed by XS code using the C<G_KEEPERR> flag.
	86
	87	C<$@> is also no longer used as an internal temporary variable when
	88	preparing to C<die>. Previously it was internally necessary to put
	89	any exception object (any non-string exception) into C<$@> first,
	90	before it could be used as an exception. (The C API still offers the
	91	old option, so an XS module might still clobber C<$@> in the old way.)
	92	This change together with the foregoing means that, in various places,
	93	C<$@> may be observed to contain its previously-assigned value, rather
	94	than having been overwritten by recent exception-related activity.
	95
	96	Warnings for C<warn> can now be objects, in the same way as exceptions
	97	for C<die>. If an object-based warning gets the default handling,
	98	of writing to standard error, it will of course still be stringified
	99	along the way. But a C<$SIG{__WARN__}> handler will now receive an
	100	object-based warning as an object, where previously it was passed the
	101	result of stringifying the object.
	102
d4438f94	103	=head1 New Platforms
	104
	105	XXX List any platforms that this version of perl compiles on, that previous
	106	versions did not. These will either be enabled by new files in the F<hints/>
	107	directories, or new subdirectories and F<README> files at the top level of the
	108	source tree.
	109
	110	=head1 Modules and Pragmata
	111
	112	XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
	113	go here. If Module::CoreList is updated, generate an initial draft of the
	114	following sections using F<Porting/corelist-perldelta.pl>, which prints stub
	115	entries to STDOUT. Results can be pasted in place of the '=head2' entries
	116	below. A paragraph summary for important changes should then be added by hand.
	117	In an ideal world, dual-life modules would have a F<Changes> file that could be
	118	cribbed.
	119
	120	=head2 New Modules and Pragmata
	121
	122	=head2 Pragmata Changes
	123
	124	=head2 Updated Modules
	125
d6445baf	126	=over
	127
	128	=item C<B::Deparse>
	129
	130	A bug has been fixed when deparsing a nextstate op that has both a
	131	change of package (relative to the previous nextstate), or a change of
	132	C<%^H> or other state, and a label. Previously the label was emitted
	133	first, leading to syntactically invalid output because a label is not
	134	permitted immediately before a package declaration, B<BEGIN> block,
	135	or some other things. Now the label is emitted last.
	136
	137	=back
	138
d4438f94	139	=head2 Removed Modules and Pragmata
	140
	141	=head1 Utility Changes
	142
	143	XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go
	144	here. Most of these are built within the directories F<utils> and F<x2p>.
	145
	146	=over 4
	147
	148	=item F<XXX>
	149
	150	XXX
	151
	152	=back
	153
	154	=head1 New Documentation
	155
	156	XXX Changes which create B<new> files in F<pod/> go here.
	157
	158	=over 4
	159
	160	=item L<XXX>
	161
	162	XXX
	163
	164	=back
	165
	166	=head1 Changes to Existing Documentation
	167
	168	XXX Changes which significantly change existing files in F<pod/> go here.
	169	Any changes to F<pod/perldiag.pod> should go in L</New or Changed Diagnostics>.
	170
	171
	172	=head1 Performance Enhancements
	173
	174	XXX Changes which enhance performance without changing behaviour go here. There
	175	may well be none in a stable release.
	176
	177	=over 4
	178
	179	=item *
	180
	181	XXX
	182
	183	=back
	184
	185	=head1 Installation and Configuration Improvements
	186
	187	XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
	188	go here.
	189
	190	=head2 Configuration improvements
	191
	192	XXX
	193
	194	=head2 Compilation improvements
	195
	196	XXX
	197
	198	=head2 Platform Specific Changes
	199
	200	=over 4
	201
	202	=item XXX-some-platform
203
204	XXX
205
206	=back
207
208	=head1 Selected Bug Fixes
209
210	XXX Important bug fixes in the core language are summarised here.
211	Bug fixes in files in F<ext/> and F<lib/> are best summarised in
212	L</Modules and Pragmata>.
213
214	=over 4
215
216	=item *
217
218	XXX
219
220	=back
221
222	=head1 New or Changed Diagnostics
223
224	XXX New or changed warnings emitted by the core's C<C> code go here.
225
226	=over 4
227
228	=item C<XXX>
229
230	XXX
231
232	=back
233
234	=head1 Changed Internals
235
236	XXX Changes which affect the interface available to C<XS> code go here.
237
238	=over 4
239
240	=item *
241
242	XXX
243
244	=back
245
246	=head1 New Tests
247
248	XXX Changes which create B<new> files in F<t/> go here. Changes to
249	existing files in F<t/> aren't worth summarising, although the bugs that
250	they represent may be.
251
252	=over 4
253
254	=item F<XXX>
255
256	XXX
257
258	=back
259
260	=head1 Known Problems
261
262	XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
263	tests that had to be C<TODO>ed for the release would be noted here, unless
264	they were specific to a particular platform (see below).
265
266	This is a list of some significant unfixed bugs, which are regressions
267	from either 5.XXX.XXX or 5.XXX.XXX.
268
269	=over 4
270
271	=item *
272
273	XXX
274
275	=back
276
277	=head1 Deprecations
278
279	XXX Add any new known deprecations here.
280
281	The following items are now deprecated.
282
283	=over 4
284
285	=item *
286
287	XXX
288
289	=back
290
291	=head1 Platform Specific Notes
292
293	XXX Any changes specific to a particular platform. VMS and Win32 are the usual
294	stars here. It's probably best to group changes under the same section layout
295	as the main perldelta
296
297	=head1 Obituary
298
299	XXX If any significant core contributor has died, we've added a short obituary
300	here.
301
302	=head1 Acknowledgements
303
304	XXX The list of people to thank goes here.
305
306
307	=head1 Reporting Bugs
308
309	If you find what you think is a bug, you might check the articles
310	recently posted to the comp.lang.perl.misc newsgroup and the perl
311	bug database at http://rt.perl.org/perlbug/ . There may also be
312	information at http://www.perl.org/ , the Perl Home Page.
313
314	If you believe you have an unreported bug, please run the B<perlbug>
315	program included with your release. Be sure to trim your bug down
316	to a tiny but sufficient test case. Your bug report, along with the
317	output of C<perl -V>, will be sent off to perlbug@perl.org to be
318	analysed by the Perl porting team.
319
320	If the bug you are reporting has security implications, which make it
321	inappropriate to send to a publicly archived mailing list, then please send
322	it to perl5-security-report@perl.org. This points to a closed subscription
323	unarchived mailing list, which includes all the core committers, who be able
324	to help assess the impact of issues, figure out a resolution, and help
325	co-ordinate the release of patches to mitigate or fix the problem across all
326	platforms on which Perl is supported. Please only use this address for
327	security issues in the Perl core, not for modules independently
328	distributed on CPAN.
329
330	=head1 SEE ALSO
331
332	The F<Changes> file for an explanation of how to view exhaustive details
333	on what changed.
334
335	The F<INSTALL> file for how to build Perl.
336
337	The F<README> file for general stuff.
338
339	The F<Artistic> and F<Copying> files for copyright information.
340
341	=cut