This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
perldelta item on PL_restartjmpenv
[perl5.git] / pod / perl5131delta.pod
CommitLineData
d4438f94
LB
1=encoding utf8
2
3=head1 NAME
4
5[ this is a template for a new perldelta file. Any text flagged as
6XXX needs to be processed before release. ]
7
8perldelta - what is new for perl v5.13.1
9
10=head1 DESCRIPTION
11
12This document describes differences between the 5.13.0 release and
13the 5.13.1 release.
14
15If you are upgrading from an earlier release such as 5.10, first read
16L<perl5120delta>, which describes differences between 5.10 and
175.12.
18
19=head1 Notice
20
21XXX Any important notices here
22
23=head1 Incompatible Changes
24
df5278db 25=head2 "C<\cI<X>>"
d4438f94 26
df5278db
KW
27The backslash-c construct was designed as a way of specifying
28non-printable characters, but there were no restrictions (on ASCII
29platforms) on what the character following the C<c> could be. Now, that
30character must be one of the ASCII characters.
d4438f94 31
72ecaef9
DM
32=head2 localised tied hashes, arrays and scalars are no longed tied
33
34In 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
43The new local array used to be made tied too, which was fairly pointless,
44and has now been fixed. This fix could however potentially cause a change
45in behaviour of some code.
46
d4438f94
LB
47=head1 Core Enhancements
48
49XXX New core language features go here. Summarise user-visible core language
50enhancements. Particularly prominent performance optimisations could go
51here, but most should go in the L</Performance Enhancements> section.
52
9d5401ce
Z
53=head2 Exception Handling Reliability
54
55Several changes have been made to the way C<die>, C<warn>, and C<$@>
56behave, in order to make them more reliable and consistent.
57
58When an exception is thrown inside an C<eval>, the exception is no
59longer at risk of being clobbered by code running during unwinding
60(e.g., destructors). Previously, the exception was written into C<$@>
61early in the throwing process, and would be overwritten if C<eval> was
62used internally in the destructor for an object that had to be freed
63while exiting from the outer C<eval>. Now the exception is written
64into C<$@> last thing before exiting the outer C<eval>, so the code
65running immediately thereafter can rely on the value in C<$@> correctly
66corresponding to that C<eval>.
67
68Likewise, a C<local $@> inside an C<eval> will no longer clobber any
69exception thrown in its scope. Previously, the restoration of C<$@> upon
70unwinding would overwrite any exception being thrown. Now the exception
71gets to the C<eval> anyway. So C<local $@> is safe inside an C<eval>,
72albeit of rather limited use.
73
74Exceptions thrown from object destructors no longer modify the C<$@>
75of the surrounding context. (If the surrounding context was exception
76unwinding, this used to be another way to clobber the exception being
77thrown. Due to the above change it no longer has that significance,
78but there are other situations where C<$@> is significant.) Previously
79such an exception was sometimes emitted as a warning, and then either
80string-appended to the surrounding C<$@> or completely replaced the
81surrounding C<$@>, depending on whether that exception and the surrounding
82C<$@> were strings or objects. Now, an exception in this situation is
83always emitted as a warning, leaving the surrounding C<$@> untouched.
84In addition to object destructors, this also affects any function call
85performed by XS code using the C<G_KEEPERR> flag.
86
87C<$@> is also no longer used as an internal temporary variable when
88preparing to C<die>. Previously it was internally necessary to put
89any exception object (any non-string exception) into C<$@> first,
90before it could be used as an exception. (The C API still offers the
91old option, so an XS module might still clobber C<$@> in the old way.)
92This change together with the foregoing means that, in various places,
93C<$@> may be observed to contain its previously-assigned value, rather
94than having been overwritten by recent exception-related activity.
95
96Warnings for C<warn> can now be objects, in the same way as exceptions
97for C<die>. If an object-based warning gets the default handling,
98of writing to standard error, it will of course still be stringified
99along the way. But a C<$SIG{__WARN__}> handler will now receive an
100object-based warning as an object, where previously it was passed the
101result of stringifying the object.
102
d4438f94
LB
103=head1 New Platforms
104
105XXX List any platforms that this version of perl compiles on, that previous
106versions did not. These will either be enabled by new files in the F<hints/>
107directories, or new subdirectories and F<README> files at the top level of the
108source tree.
109
110=head1 Modules and Pragmata
111
112XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
113go here. If Module::CoreList is updated, generate an initial draft of the
114following sections using F<Porting/corelist-perldelta.pl>, which prints stub
115entries to STDOUT. Results can be pasted in place of the '=head2' entries
116below. A paragraph summary for important changes should then be added by hand.
117In an ideal world, dual-life modules would have a F<Changes> file that could be
118cribbed.
119
120=head2 New Modules and Pragmata
121
122=head2 Pragmata Changes
123
124=head2 Updated Modules
125
d6445baf
Z
126=over
127
f8a182a2
Z
128=item Perl 4 C<.pl> libraries
129
130These historical libraries have been minimally modified to avoid using
131C<$[>. This is to prepare them for the deprecation of C<$[>.
132
d6445baf
Z
133=item C<B::Deparse>
134
135A bug has been fixed when deparsing a nextstate op that has both a
136change of package (relative to the previous nextstate), or a change of
137C<%^H> or other state, and a label. Previously the label was emitted
138first, leading to syntactically invalid output because a label is not
139permitted immediately before a package declaration, B<BEGIN> block,
140or some other things. Now the label is emitted last.
141
142=back
143
d4438f94
LB
144=head2 Removed Modules and Pragmata
145
146=head1 Utility Changes
147
148XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go
149here. Most of these are built within the directories F<utils> and F<x2p>.
150
151=over 4
152
153=item F<XXX>
154
155XXX
156
157=back
158
159=head1 New Documentation
160
161XXX Changes which create B<new> files in F<pod/> go here.
162
163=over 4
164
165=item L<XXX>
166
167XXX
168
169=back
170
171=head1 Changes to Existing Documentation
172
173XXX Changes which significantly change existing files in F<pod/> go here.
174Any changes to F<pod/perldiag.pod> should go in L</New or Changed Diagnostics>.
175
176
177=head1 Performance Enhancements
178
179XXX Changes which enhance performance without changing behaviour go here. There
180may well be none in a stable release.
181
182=over 4
183
184=item *
185
186XXX
187
188=back
189
190=head1 Installation and Configuration Improvements
191
192XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
193go here.
194
195=head2 Configuration improvements
196
197XXX
198
199=head2 Compilation improvements
200
201XXX
202
203=head2 Platform Specific Changes
204
205=over 4
206
207=item XXX-some-platform
208
209XXX
210
211=back
212
213=head1 Selected Bug Fixes
214
215XXX Important bug fixes in the core language are summarised here.
216Bug fixes in files in F<ext/> and F<lib/> are best summarised in
217L</Modules and Pragmata>.
218
219=over 4
220
221=item *
222
223XXX
224
225=back
226
227=head1 New or Changed Diagnostics
228
229XXX New or changed warnings emitted by the core's C<C> code go here.
230
231=over 4
232
233=item C<XXX>
234
235XXX
236
237=back
238
239=head1 Changed Internals
240
241XXX Changes which affect the interface available to C<XS> code go here.
242
243=over 4
244
245=item *
246
5149cfce
Z
247The protocol for unwinding the C stack at the last stage of a C<die>
248has changed how it identifies the target stack frame. This now uses
249a separate variable C<PL_restartjmpenv>, where previously it relied on
250the C<blk_eval.cur_top_env> pointer in the C<eval> context frame that
251has nominally just been discarded. This change means that code running
252during various stages of Perl-level unwinding no longer needs to take
253care to avoid destroying the ghost frame.
254
255=item *
256
d4438f94
LB
257XXX
258
259=back
260
261=head1 New Tests
262
263XXX Changes which create B<new> files in F<t/> go here. Changes to
264existing files in F<t/> aren't worth summarising, although the bugs that
265they represent may be.
266
267=over 4
268
269=item F<XXX>
270
271XXX
272
273=back
274
275=head1 Known Problems
276
277XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
278tests that had to be C<TODO>ed for the release would be noted here, unless
279they were specific to a particular platform (see below).
280
281This is a list of some significant unfixed bugs, which are regressions
282from either 5.XXX.XXX or 5.XXX.XXX.
283
284=over 4
285
286=item *
287
288XXX
289
290=back
291
292=head1 Deprecations
293
294XXX Add any new known deprecations here.
295
296The following items are now deprecated.
297
298=over 4
299
300=item *
301
302XXX
303
304=back
305
306=head1 Platform Specific Notes
307
308XXX Any changes specific to a particular platform. VMS and Win32 are the usual
309stars here. It's probably best to group changes under the same section layout
310as the main perldelta
311
312=head1 Obituary
313
314XXX If any significant core contributor has died, we've added a short obituary
315here.
316
317=head1 Acknowledgements
318
319XXX The list of people to thank goes here.
320
321
322=head1 Reporting Bugs
323
324If you find what you think is a bug, you might check the articles
325recently posted to the comp.lang.perl.misc newsgroup and the perl
326bug database at http://rt.perl.org/perlbug/ . There may also be
327information at http://www.perl.org/ , the Perl Home Page.
328
329If you believe you have an unreported bug, please run the B<perlbug>
330program included with your release. Be sure to trim your bug down
331to a tiny but sufficient test case. Your bug report, along with the
332output of C<perl -V>, will be sent off to perlbug@perl.org to be
333analysed by the Perl porting team.
334
335If the bug you are reporting has security implications, which make it
336inappropriate to send to a publicly archived mailing list, then please send
337it to perl5-security-report@perl.org. This points to a closed subscription
338unarchived mailing list, which includes all the core committers, who be able
339to help assess the impact of issues, figure out a resolution, and help
340co-ordinate the release of patches to mitigate or fix the problem across all
341platforms on which Perl is supported. Please only use this address for
342security issues in the Perl core, not for modules independently
343distributed on CPAN.
344
345=head1 SEE ALSO
346
347The F<Changes> file for an explanation of how to view exhaustive details
348on what changed.
349
350The F<INSTALL> file for how to build Perl.
351
352The F<README> file for general stuff.
353
354The F<Artistic> and F<Copying> files for copyright information.
355
356=cut