September 20th-26th
Bug reports and bug fixes
Fuzzing to find bugs
More tickets were opened by Dan Collins and Brian Carpenter, results of
fuzzing perl and uncovering interesting ways to crash perl.
Brian Carpenter found two bugs causing a null pointer dereference,
leading
to a segfault ([1]Perl #126191, [2]Perl #126192).
Brian Carpenter found a couple of assertion failures ([3]Perl #126193,
[4]Perl #126170).
Dan Collins found a double free problem ([5]Perl #126199). Vincent Pit
was
able to provide a summary of this bug in the form of:
$[ .= *[ = 'y'
which I found too cool to leave out.
Dan Collins provided a segfault ([6]Perl #126204) caused by the following
reduced regex:
/(?[()-!])/
[7]Perl #126206 is a floating point exception. Reported by Dan Collins.
[8]Perl #126042 is a stack corruption caused by perl losing track of the
stack pointer. Reported by Dan Collins, fixed by Father Chrysostomos.
Father C. raised a problem with the implementation details of PL_sv_yes,
and cautiously proposed at least a specific usage of it be removed from
perl space. Zefram supported and added that -- even if implemented
correctly -- it would still be wrong.
[9]Perl #126064: Yet another stack corruption; like the previous one,
reported by Dan Collins, fixed by Father Chrysostomos.
[10]Perl #126188: When requiring [11]IO::File in an attempt to resolve
missing method on a hash, a segfault happens. Yet more results of
fuzzing.
Reported by Dan Collins.
Ricardo Signes bumped another fuzzing bug which caused a segfault and
Shlomi Fish provided a patch, seconded by Reini Urban and discussed and
approved on #p5p - leading to the patch being applied. ([12]Perl #125350)
Portability fixes
Dan Collins provided a patch for compiling perl on GNU/Linux which was
bisected to one of the recent AmigaOS-related changes. ([13]Perl #126152)
Dan Collins reports a problem with building quadmath Perl. Bulk88
provided
more comments and Lukas Mai delved into util.c finding a potential memory
leak with the quadmath-related code. ([14]Perl #126203)
Sisyphus raised an issue of a test that has been failing for him on
Windows 7 since perl 5.23.3 having to do with read-only file attributes.
With the help of Tony Cook the packaging problem was solved. ([15]Perl
#126133)
Bulk88 provided additional information to a ticket requested to revert a
patch that caused a problem on Visual C. Karl Williamson does not wish to
revert it and instead offers to handle the specific compiler explicitly.
([16]Perl #126045)
sv_backoff optimisation
Bulk88 provided a patch for making sv_backoff more tailcall friendly
([17]Perl #126171).
sv_backoff would change its return value from int to void, but as Bulk88
explains, since it was previously only returning a meaningless constant
value and since it should be reached via the public API function
sv_setsv(sv, &PL_sv_undef) (or several others) anyway, it shouldn't be a
problem. He also added this explanation as a documentation patch.
File::Find portability issue
Robert Mah raised a problem with [18]File::Find working between CIFS and
GNU/Linux systems - one supports nlink while the other does not and
File::Find failed to understand this. Dave Mitchell showed the commit
that
tries to identify it, and additional research by Robert has shown other C
utilities seem to have this problem too. ([19]Perl #126144)
More optimisations
Bulk88 bumped a ticket he opened at the beginning of 2014 to optimize two
functions using tied hashes. The bump resulted in additional comments
from
Tony Cook, following several rounds of comments and fixes between Dave
Mitchell and Bulk88. ([20]Perl #121348)
He also provided a patch for optimizing some stack manipulation.
([21]Perl
#126196)
Mysterious mod_perl compilation crash
Additional information provided by Michael Schout on a crash involving
pre-compiling modules under mod_perl tracing back to commit which fixed a
seemingly unrelated bug. ([22]Perl #126145)
Documenting the names of types
Linda Walsh opened a ticket regarding additional reference type
documentation. Ricardo adds an explanation of Regexp vs. REGEXP and notes
additional types that should probably be documented along the way.
([23]Perl #126150)
Finding modules on case-insensitive filesystems
Patrick Zimmermann raised an issue with loading modules on
case-insensitive systems. Zefram provided an explanation on why this
happens, unfortunately a combination of correct behavior with an API
design of an optional import method in a module - something that cannot
be
changed. ([24]Perl #126167)
Crashing perl with x
Dan Collins raised a problem with the x operator causing a segfault when
operating on a list. The ticket contains an in-depth discussion on the
problem and possible fixes. ([25]Perl #125937)
What's in th %! hash
Felipe Gasper opened a ticket suggesting to document the ability to use
the values of %!. ([26]Perl #125350)
Several regexp bugs
Victor ADAM has raised a ticket that the regexp pattern ]]]]][\\ should
raise an error but does not. Karl Williamson was able to reproduce, write
a patch, and will seek additional cases before pushing it. ([27]Perl
#126141)
He opened several other regex-related tickets:
* [28]Perl #126179: Regression with \N{}.
* [29]Perl #126181: \c inside (?[]).
* [30]Perl #126182: /(.(?2))((?<=(?=(?1)).))/ hangs, eats all available
RAM.
* [31]Perl #126185: /(?-p)/ should raise an error.
* [32]Perl #126186: Document (*COMMIT:arg) and (*ACCEPT:arg).
* [33]Perl #126177: (?n) should be documented.
* [34]Perl #126187: /\p / and /\p^/ give strange warnings.
* [35]Perl #126180: /(?[\ &!])/ segfaults.
* [36]Perl #126178: /(?i/ and similar should raise an error.
Discussions
Smart Match, again
Ricardo Signes has laid out plans on cleaning up Smart Match and has
provided [37]test cases for the new expected behavior of Smart Match.
It would seem like Smart Match is going to get very clear, simple, and
most importantly, expected syntax.
The [38]thread itself is quite long and I recommend reading it only if
you're interested in what people had snagged on. The aforementioned gist
provides a clear spec of what Smart Match would become. The discussion
thread also contains some comments by Zefram on what he believes is also
confusion in Smart Match in [39]Perl 6.
Revising version string semantics
Following Lyon QA Hackathon and [40]its decisions, Ricardo Signes
provided
[41]a summary and queried for any reasoned objections to moving forward
with the recommendations. Questions were asked for clarifying specific
situations and amending was done on the linked gist.
Spaces in qr/\p L/
Karl Williamson [42]asked for comments on having spaces when using \p
(the
syntax for named Unicode properties) in regular expressions:
qr/\p L/
vs.
qr/\p L/x
Agreement that both should fail from Ricardo Signes, Yitzchak
Scott-Thoennes, and Abigail.
Removing legacy code from B
Nicolas R. [43]suggested removing "dead code" from core (specifically
[44]B relating to some PERL_VERSION checks and provided a patch removing
it. This turned into a conversation on what "dead code" is and whether it
should be removed.
Main positions:
* Dave Mitchell agrees with removing the code.
* Tony Cook applied the patch.
* Reini Urban disagrees, as it was used as boilerplate code on CPAN.
* Todd Rinaldo supports removal and suggests considering adding docs.
Continued discussion:
Rocco Caputo asked about guidelines on obsolete implementations and dead
code in general while Aristotle Pagaltzis asked to think of this change
in
the context of the recently-surfaced concept of the [45]CPAN river and
doubts whether the code in question is, in fact, dead code.
Ricardo Signes proposed a practical solution along Todd's suggestion,
opting for finding a proper place for any important information which
might be lost in this commit - documentation.
Bulk88 had offered an example with [46]Encode supporting older perl
versions with what could be described as "dead code", which Ricardo
explained as a incorrect example, since Encode can be installed on older
perl versions, while new versions of [47]B cannot.
Unshifting undef to @ISA
Vadim Pushtaev opened [48]a ticket about unshifting more than one value
to
@ISA, leading to a [49]discussion about the problem.
Zefram was able to distill that example further. Aristotle Pagaltzis
suggests this raises two bugs instead of one: A loop that occurring
pushing undef to @ISA, and unshifting multiple defined values causing
perl
to unshift undef. Eirik Berg Hanssen was able to suggest a third bug
which
occurs inside an eval showing a different behavior.
Paul "LeoNerd" Evans suggested a possible reason for the warnings which
both Vadim and Zefram agree is the real cause. The problem? In Paul's own
words:
Random guess: 'unshift' has to create multiple holes at the start of
the
array so it doesn't suffer O(n^2) behaviour.
Zefram expands:
Pretty much. ppunshift() internally performs an avunshift() followed by
a bunch of avstore()s. avunshift() doesn't take parameters for the
values to unshift; it always sticks undefs in. (Actually null pointers
internally.) The av_store() calls invoke magic on the array.
Dagfinn Ilmari Mannsåker reminds there is a separate bug unearthed during
the debugging process in which storing undef values in @main::ISA warns
101 times before dying when detecting inheritance recursion. Paul's
observation should be noted:
Oops; sounds like the code to detect and warn against the chance of an
infinite recursion bug itself suffers an infinite recursion bug.
Ilmari provided a patch to delay the @ISA set magic until all items are
assigned (which is what is done in push but not unshift).
Tony Cook explained why the original magic delay code for push (and thus
the proposed same solution for unshift) is actually wrong and offered a
different solution instead.
Ilmari offered a new patch fixing both according to Tony's suggestion.
Optimizing reference checks
At the beginning of the month Jarkko Hietaniemi [50]raised a personal
annoyance with the fact that:
ref $foo eq 'ARRAY'
actually gets compiled into a string eq against the string constant
ARRAY,
which makes it not just inefficient, but also a possible problem with
blessed references - whether arrayref or ARRAY package name, not to
mention typo possibilities.
Zefram suggested a similar solution to what [51]Params::Classify does.
Kent noted that it's Perl should have a native typeof kind of check.
Bulk88 further delved into implementation details of other languages in
this respect and what possible changes could happen in perl 5 in order to
accommodate this (and beyond). Unfortunately his email did not receive
comments.
Dereferencing and "anonymous scalars"
Bob Kleemann hit [52]a snag when trying to dereference a variable
referencing a previous variable with the same name using version numbers.
my $v = shift;
$v = \$v;
say sprintf("v%vd", $$v); # prints address, not value
Tony Cook explains it succinctly:
You're setting $v to a reference to itself, so $$v is the value of $v,
which is a reference [...].
Bob found a solution as the following code:
$v = \eval { $v };
This introduced an interesting thread on what Eirik Berg Hanssen referred
to as anonymous scalars.
By the way, following an exhaustive explanation by Aristotle Pagaltzis,
Bob eventually went with:
$v = \do { my $copy = $v };
AUTOLOAD on non-existing tied hash methods
Bulk88 [53]asks whether AUTOLOAD should be called when some methods of a
tied hash do not exist.
Chas. Owen shared code demonstrating that the only function that must be
handled is TIEHASH.
Possible optimization for tied hashes
Bulk88 [54]wondered about possibly calling scalar keys on a tied hash
instead of iterating over the keys and values, which would result in a
nice optimization. Tony Cook explained why it will not be suitable for
the
purpose.
stat with an array
Following [55]a ticket raised by Jozef Mojzis, Dan Collins [56]writes
that
a side effect of fixing at least two crash-inducing bugs, stat no longer
works on arrays. He suggests declaring it a WONTFIX or add a warning and
a
note in [57]perldelta.
Father Chrysostomos [58]adds a reasonable use-case for stat(@_) and
suggests researching additional usages before attempting to fix it, one
way or the other, and Eirik Berg Hanssen offers reasons to both document
in perldelta and raise a warning.
Dan Collins provided a patch to warn with a documentation change.
Stack overflow with XS_RETURN?
Following [59]a ticket (mentioned above) referring to the x operator
causing a segfault, Bulk88 [60]wondered whether the XS_RETURN family of
macros could introduce a segfault as well. Dave Mitchell explained how it
would not be possible, but added that maybe we should make it explicit in
the documentation and by adding assertions.
Negative values in XSRETURN
Doug Bell [61]asked what should happen when XSRETURN receives a negative
value as a parameter. Dave Mitchell, backed by H. Merijn Brand (Tux),
suggests that since this corrupts the stack, an assertion should be
added.
A patch provided and being smoked.
Branch cleanups
Dave Mitchell sent another email with [62]a list of temporary Git
branches
to be deleted, asking people to prune them.
News
perl 5.23.3 released!
Peter Martini released [63]perl 5.23.3.
His epigraph follows:
Little of of all we value here
Wakes on the morn of its hundredth year
Without both feeling and looking queer.
In fact, there’s nothing that keeps its youth,
So far as I know, but a tree and truth.
(This is a moral that runs at large;
Take it. — You’re welcome. — No extra charge.)
-- The Deacon’s Masterpiece or The Wonderful "One-Hoss Shay": A
Logical Story
Oliver Wendell Holmes
[64]The announcement.
Encode 2.78 is out
Dan Kogai announced a new version of [65]Encode. Biggest change is
preloading the CP1252 encoding.
References
Visible links
1. https://rt.perl.org/Ticket/Display.html?id=126191
2. https://rt.perl.org/Ticket/Display.html?id=126192
3. https://rt.perl.org/Ticket/Display.html?id=126193
4. https://rt.perl.org/Ticket/Display.html?id=126170
5. https://rt.perl.org/Ticket/Display.html?id=126199
6. https://rt.perl.org/Ticket/Display.html?id=126204
7. https://rt.perl.org/Ticket/Display.html?id=126206
8. https://rt.perl.org/Ticket/Display.html?id=126042
9. https://rt.perl.org/Ticket/Display.html?id=126064
10. https://rt.perl.org/Ticket/Display.html?id=126188
11. https://metacpan.org/pod/IO::File
12. https://rt.perl.org/Ticket/Display.html?id=125350
13. https://rt.perl.org/Ticket/Display.html?id=126152
14. https://rt.perl.org/Ticket/Display.html?id=126203
15. https://rt.perl.org/Ticket/Display.html?id=126133
16. https://rt.perl.org/Ticket/Display.html?id=126045
17. https://rt.perl.org/Ticket/Display.html?id=126171
18. https://metacpan.org/pod/File::Find
19. https://rt.perl.org/Ticket/Display.html?id=126144
20. https://rt.perl.org/Public/Bug/Display.html?id=121348
21. https://rt.perl.org/Ticket/Display.html?id=126196
22. https://rt.perl.org/Ticket/Display.html?id=126145
23. https://rt.perl.org/Ticket/Display.html?id=126150
24. https://rt.perl.org/Ticket/Display.html?id=126167
25. https://rt.perl.org/Ticket/Display.html?id=125937
26. https://rt.perl.org/Ticket/Display.html?id=126174
27. https://rt.perl.org/Ticket/Display.html?id=126141
28. https://rt.perl.org/Ticket/Display.html?id=126179
29. https://rt.perl.org/Ticket/Display.html?id=126181
30. https://rt.perl.org/Ticket/Display.html?id=126182
31. https://rt.perl.org/Ticket/Display.html?id=126185
32. https://rt.perl.org/Ticket/Display.html?id=126186
33. https://rt.perl.org/Ticket/Display.html?id=126177
34. https://rt.perl.org/Ticket/Display.html?id=126187
35. https://rt.perl.org/Ticket/Display.html?id=126180
36. https://rt.perl.org/Ticket/Display.html?id=126178
37. https://gist.github.com/rjbs/fb5716d7dbd4f23939ea
38.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg230881.html
39.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231292.html
40. https://gist.github.com/dagolden/9559280
41.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231216.html
42.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231263.html
43.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg230985.html
44. https://metacpan.org/pod/B
45. http://neilb.org/tag/cpan-river/
46. https://metacpan.org/pod/Encode
47. https://metacpan.org/pod/B
48. https://rt.perl.org/Ticket/Display.html?id=126082
49.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231063.html
50.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg230637.html
51. https://metacpan.org/pod/Params::Classify
52.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231048.html
53.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231207.html
54.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231210.html
55. https://rt.perl.org/Ticket/Display.html?id=126162
56.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231304.html
57. https://metacpan.org/pod/perldelta
58.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231309.html
59. https://rt.perl.org/Ticket/Display.html?id=125937
60.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231329.html
61.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/06/msg228284.html
62.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231254.html
63. https://metacpan.org/release/PCM/perl-5.23.3/
64.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231173.html
65. https://metacpan.org/pod/Encode
September 20th-26th
Bug reports and bug fixes
Fuzzing to find bugs
More tickets were opened by Dan Collins and Brian Carpenter, results of
fuzzing perl and uncovering interesting ways to crash perl.
Brian Carpenter found two bugs causing a null pointer dereference,
leading
to a segfault ([1]Perl #126191, [2]Perl #126192).
Brian Carpenter found a couple of assertion failures ([3]Perl #126193,
[4]Perl #126170).
Dan Collins found a double free problem ([5]Perl #126199). Vincent Pit
was
able to provide a summary of this bug in the form of:
$[ .= *[ = 'y'
which I found too cool to leave out.
Dan Collins provided a segfault ([6]Perl #126204) caused by the following
reduced regex:
/(?[()-!])/
[7]Perl #126206 is a floating point exception. Reported by Dan Collins.
[8]Perl #126042 is a stack corruption caused by perl losing track of the
stack pointer. Reported by Dan Collins, fixed by Father Chrysostomos.
Father C. raised a problem with the implementation details of PL_sv_yes,
and cautiously proposed at least a specific usage of it be removed from
perl space. Zefram supported and added that -- even if implemented
correctly -- it would still be wrong.
[9]Perl #126064: Yet another stack corruption; like the previous one,
reported by Dan Collins, fixed by Father Chrysostomos.
[10]Perl #126188: When requiring [11]IO::File in an attempt to resolve
missing method on a hash, a segfault happens. Yet more results of
fuzzing.
Reported by Dan Collins.
Ricardo Signes bumped another fuzzing bug which caused a segfault and
Shlomi Fish provided a patch, seconded by Reini Urban and discussed and
approved on #p5p - leading to the patch being applied. ([12]Perl #125350)
Portability fixes
Dan Collins provided a patch for compiling perl on GNU/Linux which was
bisected to one of the recent AmigaOS-related changes. ([13]Perl #126152)
Dan Collins reports a problem with building quadmath Perl. Bulk88
provided
more comments and Lukas Mai delved into util.c finding a potential memory
leak with the quadmath-related code. ([14]Perl #126203)
Sisyphus raised an issue of a test that has been failing for him on
Windows 7 since perl 5.23.3 having to do with read-only file attributes.
With the help of Tony Cook the packaging problem was solved. ([15]Perl
#126133)
Bulk88 provided additional information to a ticket requested to revert a
patch that caused a problem on Visual C. Karl Williamson does not wish to
revert it and instead offers to handle the specific compiler explicitly.
([16]Perl #126045)
sv_backoff optimisation
Bulk88 provided a patch for making sv_backoff more tailcall friendly
([17]Perl #126171).
sv_backoff would change its return value from int to void, but as Bulk88
explains, since it was previously only returning a meaningless constant
value and since it should be reached via the public API function
sv_setsv(sv, &PL_sv_undef) (or several others) anyway, it shouldn't be a
problem. He also added this explanation as a documentation patch.
File::Find portability issue
Robert Mah raised a problem with [18]File::Find working between CIFS and
GNU/Linux systems - one supports nlink while the other does not and
File::Find failed to understand this. Dave Mitchell showed the commit
that
tries to identify it, and additional research by Robert has shown other C
utilities seem to have this problem too. ([19]Perl #126144)
More optimisations
Bulk88 bumped a ticket he opened at the beginning of 2014 to optimize two
functions using tied hashes. The bump resulted in additional comments
from
Tony Cook, following several rounds of comments and fixes between Dave
Mitchell and Bulk88. ([20]Perl #121348)
He also provided a patch for optimizing some stack manipulation.
([21]Perl
#126196)
Mysterious mod_perl compilation crash
Additional information provided by Michael Schout on a crash involving
pre-compiling modules under mod_perl tracing back to commit which fixed a
seemingly unrelated bug. ([22]Perl #126145)
Documenting the names of types
Linda Walsh opened a ticket regarding additional reference type
documentation. Ricardo adds an explanation of Regexp vs. REGEXP and notes
additional types that should probably be documented along the way.
([23]Perl #126150)
Finding modules on case-insensitive filesystems
Patrick Zimmermann raised an issue with loading modules on
case-insensitive systems. Zefram provided an explanation on why this
happens, unfortunately a combination of correct behavior with an API
design of an optional import method in a module - something that cannot
be
changed. ([24]Perl #126167)
Crashing perl with x
Dan Collins raised a problem with the x operator causing a segfault when
operating on a list. The ticket contains an in-depth discussion on the
problem and possible fixes. ([25]Perl #125937)
What's in th %! hash
Felipe Gasper opened a ticket suggesting to document the ability to use
the values of %!. ([26]Perl #125350)
Several regexp bugs
Victor ADAM has raised a ticket that the regexp pattern ]]]]][\\ should
raise an error but does not. Karl Williamson was able to reproduce, write
a patch, and will seek additional cases before pushing it. ([27]Perl
#126141)
He opened several other regex-related tickets:
* [28]Perl #126179: Regression with \N{}.
* [29]Perl #126181: \c inside (?[]).
* [30]Perl #126182: /(.(?2))((?<=(?=(?1)).))/ hangs, eats all available
RAM.
* [31]Perl #126185: /(?-p)/ should raise an error.
* [32]Perl #126186: Document (*COMMIT:arg) and (*ACCEPT:arg).
* [33]Perl #126177: (?n) should be documented.
* [34]Perl #126187: /\p / and /\p^/ give strange warnings.
* [35]Perl #126180: /(?[\ &!])/ segfaults.
* [36]Perl #126178: /(?i/ and similar should raise an error.
Discussions
Smart Match, again
Ricardo Signes has laid out plans on cleaning up Smart Match and has
provided [37]test cases for the new expected behavior of Smart Match.
It would seem like Smart Match is going to get very clear, simple, and
most importantly, expected syntax.
The [38]thread itself is quite long and I recommend reading it only if
you're interested in what people had snagged on. The aforementioned gist
provides a clear spec of what Smart Match would become. The discussion
thread also contains some comments by Zefram on what he believes is also
confusion in Smart Match in [39]Perl 6.
Revising version string semantics
Following Lyon QA Hackathon and [40]its decisions, Ricardo Signes
provided
[41]a summary and queried for any reasoned objections to moving forward
with the recommendations. Questions were asked for clarifying specific
situations and amending was done on the linked gist.
Spaces in qr/\p L/
Karl Williamson [42]asked for comments on having spaces when using \p
(the
syntax for named Unicode properties) in regular expressions:
qr/\p L/
vs.
qr/\p L/x
Agreement that both should fail from Ricardo Signes, Yitzchak
Scott-Thoennes, and Abigail.
Removing legacy code from B
Nicolas R. [43]suggested removing "dead code" from core (specifically
[44]B relating to some PERL_VERSION checks and provided a patch removing
it. This turned into a conversation on what "dead code" is and whether it
should be removed.
Main positions:
* Dave Mitchell agrees with removing the code.
* Tony Cook applied the patch.
* Reini Urban disagrees, as it was used as boilerplate code on CPAN.
* Todd Rinaldo supports removal and suggests considering adding docs.
Continued discussion:
Rocco Caputo asked about guidelines on obsolete implementations and dead
code in general while Aristotle Pagaltzis asked to think of this change
in
the context of the recently-surfaced concept of the [45]CPAN river and
doubts whether the code in question is, in fact, dead code.
Ricardo Signes proposed a practical solution along Todd's suggestion,
opting for finding a proper place for any important information which
might be lost in this commit - documentation.
Bulk88 had offered an example with [46]Encode supporting older perl
versions with what could be described as "dead code", which Ricardo
explained as a incorrect example, since Encode can be installed on older
perl versions, while new versions of [47]B cannot.
Unshifting undef to @ISA
Vadim Pushtaev opened [48]a ticket about unshifting more than one value
to
@ISA, leading to a [49]discussion about the problem.
Zefram was able to distill that example further. Aristotle Pagaltzis
suggests this raises two bugs instead of one: A loop that occurring
pushing undef to @ISA, and unshifting multiple defined values causing
perl
to unshift undef. Eirik Berg Hanssen was able to suggest a third bug
which
occurs inside an eval showing a different behavior.
Paul "LeoNerd" Evans suggested a possible reason for the warnings which
both Vadim and Zefram agree is the real cause. The problem? In Paul's own
words:
Random guess: 'unshift' has to create multiple holes at the start of
the
array so it doesn't suffer O(n^2) behaviour.
Zefram expands:
Pretty much. ppunshift() internally performs an avunshift() followed by
a bunch of avstore()s. avunshift() doesn't take parameters for the
values to unshift; it always sticks undefs in. (Actually null pointers
internally.) The av_store() calls invoke magic on the array.
Dagfinn Ilmari Mannsåker reminds there is a separate bug unearthed during
the debugging process in which storing undef values in @main::ISA warns
101 times before dying when detecting inheritance recursion. Paul's
observation should be noted:
Oops; sounds like the code to detect and warn against the chance of an
infinite recursion bug itself suffers an infinite recursion bug.
Ilmari provided a patch to delay the @ISA set magic until all items are
assigned (which is what is done in push but not unshift).
Tony Cook explained why the original magic delay code for push (and thus
the proposed same solution for unshift) is actually wrong and offered a
different solution instead.
Ilmari offered a new patch fixing both according to Tony's suggestion.
Optimizing reference checks
At the beginning of the month Jarkko Hietaniemi [50]raised a personal
annoyance with the fact that:
ref $foo eq 'ARRAY'
actually gets compiled into a string eq against the string constant
ARRAY,
which makes it not just inefficient, but also a possible problem with
blessed references - whether arrayref or ARRAY package name, not to
mention typo possibilities.
Zefram suggested a similar solution to what [51]Params::Classify does.
Kent noted that it's Perl should have a native typeof kind of check.
Bulk88 further delved into implementation details of other languages in
this respect and what possible changes could happen in perl 5 in order to
accommodate this (and beyond). Unfortunately his email did not receive
comments.
Dereferencing and "anonymous scalars"
Bob Kleemann hit [52]a snag when trying to dereference a variable
referencing a previous variable with the same name using version numbers.
my $v = shift;
$v = \$v;
say sprintf("v%vd", $$v); # prints address, not value
Tony Cook explains it succinctly:
You're setting $v to a reference to itself, so $$v is the value of $v,
which is a reference [...].
Bob found a solution as the following code:
$v = \eval { $v };
This introduced an interesting thread on what Eirik Berg Hanssen referred
to as anonymous scalars.
By the way, following an exhaustive explanation by Aristotle Pagaltzis,
Bob eventually went with:
$v = \do { my $copy = $v };
AUTOLOAD on non-existing tied hash methods
Bulk88 [53]asks whether AUTOLOAD should be called when some methods of a
tied hash do not exist.
Chas. Owen shared code demonstrating that the only function that must be
handled is TIEHASH.
Possible optimization for tied hashes
Bulk88 [54]wondered about possibly calling scalar keys on a tied hash
instead of iterating over the keys and values, which would result in a
nice optimization. Tony Cook explained why it will not be suitable for
the
purpose.
stat with an array
Following [55]a ticket raised by Jozef Mojzis, Dan Collins [56]writes
that
a side effect of fixing at least two crash-inducing bugs, stat no longer
works on arrays. He suggests declaring it a WONTFIX or add a warning and
a
note in [57]perldelta.
Father Chrysostomos [58]adds a reasonable use-case for stat(@_) and
suggests researching additional usages before attempting to fix it, one
way or the other, and Eirik Berg Hanssen offers reasons to both document
in perldelta and raise a warning.
Dan Collins provided a patch to warn with a documentation change.
Stack overflow with XS_RETURN?
Following [59]a ticket (mentioned above) referring to the x operator
causing a segfault, Bulk88 [60]wondered whether the XS_RETURN family of
macros could introduce a segfault as well. Dave Mitchell explained how it
would not be possible, but added that maybe we should make it explicit in
the documentation and by adding assertions.
Negative values in XSRETURN
Doug Bell [61]asked what should happen when XSRETURN receives a negative
value as a parameter. Dave Mitchell, backed by H. Merijn Brand (Tux),
suggests that since this corrupts the stack, an assertion should be
added.
A patch provided and being smoked.
Branch cleanups
Dave Mitchell sent another email with [62]a list of temporary Git
branches
to be deleted, asking people to prune them.
News
perl 5.23.3 released!
Peter Martini released [63]perl 5.23.3.
His epigraph follows:
Little of of all we value here
Wakes on the morn of its hundredth year
Without both feeling and looking queer.
In fact, there’s nothing that keeps its youth,
So far as I know, but a tree and truth.
(This is a moral that runs at large;
Take it. — You’re welcome. — No extra charge.)
-- The Deacon’s Masterpiece or The Wonderful "One-Hoss Shay": A
Logical Story
Oliver Wendell Holmes
[64]The announcement.
Encode 2.78 is out
Dan Kogai announced a new version of [65]Encode. Biggest change is
preloading the CP1252 encoding.
References
Visible links
1. https://rt.perl.org/Ticket/Display.html?id=126191
2. https://rt.perl.org/Ticket/Display.html?id=126192
3. https://rt.perl.org/Ticket/Display.html?id=126193
4. https://rt.perl.org/Ticket/Display.html?id=126170
5. https://rt.perl.org/Ticket/Display.html?id=126199
6. https://rt.perl.org/Ticket/Display.html?id=126204
7. https://rt.perl.org/Ticket/Display.html?id=126206
8. https://rt.perl.org/Ticket/Display.html?id=126042
9. https://rt.perl.org/Ticket/Display.html?id=126064
10. https://rt.perl.org/Ticket/Display.html?id=126188
11. https://metacpan.org/pod/IO::File
12. https://rt.perl.org/Ticket/Display.html?id=125350
13. https://rt.perl.org/Ticket/Display.html?id=126152
14. https://rt.perl.org/Ticket/Display.html?id=126203
15. https://rt.perl.org/Ticket/Display.html?id=126133
16. https://rt.perl.org/Ticket/Display.html?id=126045
17. https://rt.perl.org/Ticket/Display.html?id=126171
18. https://metacpan.org/pod/File::Find
19. https://rt.perl.org/Ticket/Display.html?id=126144
20. https://rt.perl.org/Public/Bug/Display.html?id=121348
21. https://rt.perl.org/Ticket/Display.html?id=126196
22. https://rt.perl.org/Ticket/Display.html?id=126145
23. https://rt.perl.org/Ticket/Display.html?id=126150
24. https://rt.perl.org/Ticket/Display.html?id=126167
25. https://rt.perl.org/Ticket/Display.html?id=125937
26. https://rt.perl.org/Ticket/Display.html?id=126174
27. https://rt.perl.org/Ticket/Display.html?id=126141
28. https://rt.perl.org/Ticket/Display.html?id=126179
29. https://rt.perl.org/Ticket/Display.html?id=126181
30. https://rt.perl.org/Ticket/Display.html?id=126182
31. https://rt.perl.org/Ticket/Display.html?id=126185
32. https://rt.perl.org/Ticket/Display.html?id=126186
33. https://rt.perl.org/Ticket/Display.html?id=126177
34. https://rt.perl.org/Ticket/Display.html?id=126187
35. https://rt.perl.org/Ticket/Display.html?id=126180
36. https://rt.perl.org/Ticket/Display.html?id=126178
37. https://gist.github.com/rjbs/fb5716d7dbd4f23939ea
38.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg230881.html
39.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231292.html
40. https://gist.github.com/dagolden/9559280
41.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231216.html
42.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231263.html
43.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg230985.html
44. https://metacpan.org/pod/B
45. http://neilb.org/tag/cpan-river/
46. https://metacpan.org/pod/Encode
47. https://metacpan.org/pod/B
48. https://rt.perl.org/Ticket/Display.html?id=126082
49.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231063.html
50.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg230637.html
51. https://metacpan.org/pod/Params::Classify
52.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231048.html
53.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231207.html
54.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231210.html
55. https://rt.perl.org/Ticket/Display.html?id=126162
56.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231304.html
57. https://metacpan.org/pod/perldelta
58.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231309.html
59. https://rt.perl.org/Ticket/Display.html?id=125937
60.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231329.html
61.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/06/msg228284.html
62.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231254.html
63. https://metacpan.org/release/PCM/perl-5.23.3/
64.
http://www.nntp.perl.org/group/perl.perl5.porters/2015/09/msg231173.html
65. https://metacpan.org/pod/Encode
