=head1 DESCRIPTION
-This document describes differences between the 5.6.0 release and the
-5.8.0 release.
+This document describes differences between the 5.6.0 release
+and the 5.8.0 release.
+
+Many of the bug fixes in 5.8.0 were already seen in the 5.6.1
+maintenance release since the two releases were kept closely
+coordinated.
+
+If you are upgrading from Perl 5.005_03, you might also want
+to read L<perl56delta>.
+
+=head1 Highlights In 5.8.0
+
+=over 4
+
+=item *
+
+Better Unicode support
+
+=item *
+
+New Thread Implementation
+
+=item *
+
+Many New Modules
+
+=item *
+
+Better Numeric Accuracy
+
+=item *
+
+Safe Signals
+
+=item *
+
+More Extensive Regression Testing
+
+=back
=head1 Incompatible Changes
TCP/IP stacks of VMS: we do not know since we weren't able to test
Perl in such configurations.
+=head2 IEEE-format Floating Point Default on OpenVMS Alpha
+
+Perl now uses IEEE format (T_FLOAT) as the default internal floating
+point format on OpenVMS Alpha, potentially breaking binary compatibility
+with external libraries or existing data. G_FLOAT is still available as
+a configuration option. The default on VAX (D_FLOAT) has not changed.
+
=head2 Different Definition of the Unicode Character Classes \p{In...}
As suggested by the Unicode consortium, the Unicode character classes
=item *
The list of filenames from glob() (or <...>) is now by default sorted
-alphabetically to be csh-compliant. (bsd_glob() does still sort platform
+alphabetically to be csh-compliant (which is what happened before
+in most UNIX platforms). (bsd_glob() does still sort platform
natively, ASCII or EBCDIC, unless GLOB_ALPHASORT is specified.)
=item *
+Spurious syntax errors generated in certain situations, when glob()
+caused File::Glob to be loaded for the first time, have been fixed.
+
+=item *
+
Although "you shouldn't do that", it was possible to write code that
depends on Perl's hashed key order (Data::Dumper does this). The new
algorithm "One-at-a-Time" produces a different hashed key order.
=item *
-The syntaxes C<< @a->[...] >> and C<< %h->{...}>> have now been deprecated.
+The syntaxes C<< @a->[...] >> and C<< %h->{...} >> have now been deprecated.
=item *
=item *
Lvalue subroutines can now return C<undef> in list context.
+However, the lvalue subroutine feature still remains experimental.
=item *
print "%2\$s %1\$s\n", "foo", "bar";
-will print "bar foo\n"; This feature helps in writing
-internationalised software.
+will print "bar foo\n". This feature helps in writing
+internationalised software, and in general when the order
+of the parameters can vary.
=item *
=item *
-UNTIE method is now recognised.
+untie() will now call an UNTIE() hook if it exists. See L<perltie>
+for details.
=item *
=item *
-C<Test::Simple> has the- basic utilities for writing tests, by Michael
+C<Test::Simple> has basic utilities for writing tests, by Michael
Schwern. See L<Test::Simple>.
=item *
=item *
+DB_File now supports newer Berkeley DB versions, among
+other improvements.
+
+=item *
+
The English module can now be used without the infamous performance
hit by saying
=item *
+File::Find now chdir()s correctly when chasing symbolic links.
+
+=item *
+
File::Find now has pre- and post-processing callbacks. It also
correctly changes directories when chasing symbolic links. Callbacks
(naughtily) exiting with "next;" instead of "return;" now work.
=item *
+Math::Complex handles inf, NaN etc., better.
+
+=item *
+
Net::Ping has been enhanced. There is now "external" protocol which
uses Net::Ping::External module which runs external ping(1) and parses
-the output. An alpha version of Net::Ping::External is available in
-CPAN and in 5.7.2 the Net::Ping::External may be integrated to Perl.
+the output. A version of Net::Ping::External is available in CPAN.
=item *
-C<POSIX::sigaction()> is now much more flexible and robust.
+POSIX::sigaction() is now much more flexible and robust.
You can now install coderef handlers, 'DEFAULT', and 'IGNORE'
handlers, installing new handlers was not atomic.
=item *
-C<%INC> now localised in a Safe compartment so that use/require work.
+In Safe the C<%INC> now localised in a Safe compartment so that
+use/require work.
+
+=item *
+
+In SDBM_File on dosish platforms, some keys went missing because of
+lack of support for files with "holes". A workaround for the problem
+has been added.
+
+=item *
+
+In Search::Dict one can now have a pre-processing hook for the
+lines being searched.
=item *
=item *
-The C<vars> pragma now supports declaring fully qualified variables.
+The vars pragma now supports declaring fully qualified variables.
(Something that C<our()> does not and will not support.)
=item *
C<perlcc> has been rewritten and its user interface (that is,
command line) is much more like that of the UNIX C compiler, cc.
+(The perlbc tools has been removed. Use C<perlcc -B> instead.)
=item *
-C<perlivp> is a new utility for doing Installation Verification
-Procedure after installing Perl.
+C<perlivp> is a new Installation Verification Procedure utility
+for running any time after installing Perl.
=item *
=item *
perlebcdic contains considerations for running Perl on EBCDIC platforms.
-Note that unfortunately EBCDIC platforms that used to be supported back
-in Perl 5.005 are still unsupported by Perl 5.8.0; the plan, however, is
-to bring them back to the fold.
=item *
=item *
+perlpacktut is a pack() tutorial.
+
+=item *
+
perlpod has been rewritten to be clearer and to record the best
practices gathered over the years.
=item *
-perlposix-bc explains using Perl on the POSIX-BC platform
-(an EBCDIC mainframe platform).
-
-=item *
-
perlretut is a regular expression tutorial.
=item *
=item *
-map() that changes the size of the list should now work faster.
+map() could get pathologically slow when the result list it generates
+is larger than the source list. The performance has been improved for
+common scenarios.
=item *
(meaning that elements with identical keys will stay ordered as they
were before the sort). See the C<sort> pragma for information.
+The story in more detail: suppose you want to serve yourself a little
+slice of Pi.
+
+ @digits = ( 3,1,4,1,5,9 );
+
+A numerical sort of the digits will yield (1,1,3,4,5,9), as expected.
+Which C<1> comes first is hard to know, since one C<1> looks pretty
+much like any other. You can regard this as totally trivial,
+or somewhat profound. However, if you just want to sort the even
+digits ahead of the odd ones, then what will
+
+ sort { ($a % 2) <=> ($b % 2) } @digits;
+
+yield? The only even digit, C<4>, will come first. But how about
+the odd numbers, which all compare equal? With the quicksort algorithm
+used to implement Perl 5.6 and earlier, the order of ties is left up
+to the sort. So, as you add more and more digits of Pi, the order
+in which the sorted even and odd digits appear will change.
+and, for sufficiently large slices of Pi, the quicksort algorithm
+in Perl 5.8 won't return the same results even if reinvoked with the
+same input. The justification for this rests with quicksort's
+worst case behavior. If you run
+
+ sort { $a <=> $b } ( 1 .. $N , 1 .. $N );
+
+(something you might approximate if you wanted to merge two sorted
+arrays using sort), doubling $N doesn't just double the quicksort time,
+it I<quadruples> it. Quicksort has a worst case run time that can
+grow like N**2, so-called I<quadratic> behaviour, and it can happen
+on patterns that may well arise in normal use. You won't notice this
+for small arrays, but you I<will> notice it with larger arrays,
+and you may not live long enough for the sort to complete on arrays
+of a million elements. So the 5.8 quicksort scrambles large arrays
+before sorting them, as a statistical defence against quadratic behaviour.
+But that means if you sort the same large array twice, ties may be
+broken in different ways.
+
+Because of the unpredictability of tie-breaking order, and the quadratic
+worst-case behaviour, quicksort was I<almost> replaced completely with
+a stable mergesort. I<Stable> means that ties are broken to preserve
+the original order of appearance in the input array. So
+
+ sort { ($a % 2) <=> ($b % 2) } (3,1,4,1,5,9);
+
+will yield (4,3,1,1,5,9), guaranteed. The even and odd numbers
+appear in the output in the same order they appeared in the input.
+Mergesort has worst case O(NlogN) behaviour, the best value
+attainable. And, ironically, this mergesort does particularly
+well where quicksort goes quadratic: mergesort sorts (1..$N, 1..$N)
+in O(N) time. But quicksort was rescued at the last moment because
+it is faster than mergesort on certain inputs and platforms.
+For example, if you really I<don't> care about the order of even
+and odd digits, quicksort will run in O(N) time; it's very good
+at sorting many repetitions of a small number of distinct elements.
+The quicksort divide and conquer strategy works well on platforms
+with relatively small, very fast, caches. Eventually, the problem gets
+whittled down to one that fits in the cache, from which point it
+benefits from the increased memory speed.
+
+Quicksort was rescued by implementing a sort pragma to control aspects
+of the sort. The B<stable> subpragma forces stable behaviour,
+regardless of algorithm. The B<_quicksort> and B<_mergesort>
+subpragmas are heavy-handed ways to select the underlying implementation.
+The leading C<_> is a reminder that these subpragmas may not survive
+beyond 5.8. More appropriate mechanisms for selecting the implementation
+exist, but they wouldn't have arrived in time to save quicksort.
+
=item *
Hashes now use Bob Jenkins "One-at-a-Time" hashing key algorithm
=item *
+Configure support for pdp11-style memory models has been removed due
+to obsolescence.
+
+=item *
+
configure.gnu now works with options with whitespace in them.
=item *
=item *
+NEC SUPER-UX is now supported.
+
+=item *
+
Amdahl UTS UNIX mainframe platform is now supported.
=item *
=item *
+caller() could cause core dumps in certain situations. Carp was sometimes
+affected by this problem.
+
+=item *
+
chop(@list) in list context returned the characters chopped in
reverse order. This has been reversed to be in the right order.
Several debugger fixes: exit code now reflects the script exit code,
condition C<"0"> now treated correctly, the C<d> command now checks
-line number, the C<$.> no longer gets corrupted, all debugger output now
-goes correctly to the socket if RemotePort is set.
+line number, the C<$.> no longer gets corrupted, all debugger output
+now goes correctly to the socket if RemotePort is set.
+
+=item *
+
+Perl 5.6.0 could emit spurious warnings about redefinition of dl_error()
+when statically building extensions into perl. This has been corrected.
=item *
=item *
C<*foo{FORMAT}> now works.
+=item *
+
+Infinity is now recognized as a number.
=item *
=item *
-Lexical warnings now propagating correctly between scopes.
+Lexical warnings now propagating correctly between scopes
+and into C<eval "...">.
+
+=item *
+
+C<use warnings qw(FATAL all)> did not work as intended. This has been
+corrected.
+
+=item *
+
+warnings::enabled() now reports the state of $^W correctly if the caller
+isn't using lexical warnings.
=item *
=item *
+Numeric conversions did not recognize changes in the string value
+properly in certain circumstances.
+
+=item *
+
Attributes (like :shared) didn't work with our().
=item *
=item *
+"our" variables of the same name declared in two sibling blocks
+resulted in bogus warnings about "redeclaration" of the variables.
+The problem has been corrected.
+
+=item *
+
pack "Z" now correctly terminates the string with "\0".
=item *
=item *
-C<q(a\\b)> now parses correctly as C<'a\\b'>.
+C<qw(a\\b)> now parses correctly as C<'a\\b'>.
+
+=item *
+
+pos() did not return the correct value within s///ge in earlier
+versions. This is now handled correctly.
=item *
sort() arguments are now compiled in the right wantarray context
(they were accidentally using the context of the sort() itself).
+The comparison block is now run in scalar context, and the arguments
+to be sorted are always provided list context.
=item *
=item *
+Some cases of inconsistent taint propagation (such as within hash
+values) have been fixed.
+
+=item *
+
+The RE engine found in Perl 5.6.0 accidentally pessimised certain kinds
+of simple pattern matches. These are now handled better.
+
+=item *
+
+Regular expression debug output (whether through C<use re 'debug'>
+or via C<-Dr>) now looks better.
+
+=item *
+
+Multi-line matches like C<"a\nxb\n" =~ /(?!\A)x/m> were flawed. The
+bug has been fixed.
+
+=item *
+
+Use of $& could trigger a core dump under some situations. This
+is now avoided.
+
+=item *
+
The regular expression captured submatches ($1, $2, ...) are now
more consistently unset if the match fails, instead of leaving false
data lying around in them.
=item *
-C<Sys::Syslog> ignored the C<LOG_AUTH> constant.
+readline() on files opened in "slurp" mode could return an extra "" at
+the end in certain situations. This has been corrected.
+
+=item *
+
+Autovivification of symbolic references of special variables described
+in L<perlvar> (as in C<${$num}>) was accidentally disabled. This works
+again now.
+
+=item *
+
+Sys::Syslog ignored the C<LOG_AUTH> constant.
=item *
=item *
+Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to spurious warnings.
+This has been corrected.
+
+=item *
+
Zero entries were missing from the Unicode classes like C<IsDigit>.
=back
+=item *
+
+Large unsigned numbers (those above 2**31) could sometimes lose their
+unsignedness, causing bogus results in arithmetic operations.
+
=back
=head2 Platform Specific Changes and Fixes
chdir() now works better despite a CRT bug; now works with MULTIPLICITY
(see INSTALL); now works with Perl's malloc.
+The tainting of C<%ENV> elements via C<keys> or C<values> was previously
+unimplemented. It now works as documented.
+
+The C<waitpid> emulation has been improved. The worst bug (now fixed)
+was that a pid of -1 would cause a wildcard search of all processes on
+the system. The most significant enhancement is that we can now
+usually get the completion status of a terminated process.
+
+POSIX-style signals are now emulated much better on VMS versions prior
+to 7.0.
+
+The C<system> function and backticks operator have improved
+functionality and better error handling.
+
=item *
Windows
=item *
+Current directory entries in %ENV are now correctly propagated to child
+processes.
+
+=item *
+
$ENV{LIB} now used to search for libs under Visual C.
=item *
-Win32::GetCwd() correctly returns C:\ instead of C: when at the drive root.
-Other bugs in chdir() and Cwd::cwd() have also been fixed.
+fork() emulation has been improved in various ways, but still continues
+to be experimental. See L<perlfork> for known bugs and caveats.
=item *
=item *
+Win32::GetCwd() correctly returns C:\ instead of C: when at the drive root.
+Other bugs in chdir() and Cwd::cwd() have also been fixed.
+
+=item *
+
HTML files will be installed in c:\perl\html instead of c:\perl\lib\pod\html
=item *
=item *
+%SIG has been enabled under USE_ITHREADS, but its use is completely
+unsupported under all configurations.
+
+=item *
+
Less stack reserved per thread so that more threads can run
concurrently. (Still 16M per thread.)
=item *
-wait() and waitpid() now work much better.
+wait(), waitpid() and backticks now return the correct exit status under
+Windows 9x.
=item *
=head1 New Tests
-Several new tests have been added, especially for the F<lib> subsection.
+Several new tests have been added, especially for the F<lib>
+subsection. There are now about 34 000 individual tests (spread over
+about 530 test scripts), in the regression suite (5.6.1 has about
+11700 tests, in 258 test scripts) Many of the new tests are introduced
+by the new modules, but still in general Perl is now more thoroughly
+tested.
+
+Because of the large number of tests, running the regression suite
+will take considerably longer time than it used to: expect the suite
+to take up to 4-5 times longer to run than in perl 5.6. In a really
+fast machine you can hope to finish the suite in about 5 minutes
+(wallclock time).
The tests are now reported in a different order than in earlier Perls.
(This happens because the test scripts from under t/lib have been moved
=head1 Known Problems
-Note that unlike other sections in this document (which describe
-changes since 5.7.0) this section is cumulative containing known
-problems for all the 5.7 releases.
-
=head2 AIX
=over 4
No known fix.
+=head2 Mac OS X
+
+The following tests are known to fail:
+
+ Failed Test Stat Wstat Total Fail Failed List of Failed
+ -------------------------------------------------------------------------
+ ../ext/DB_File/t/db-btree.t 0 11 ?? ?? % ??
+ ../ext/DB_File/t/db-recno.t 149 3 2.01% 61 63 65
+ ../ext/POSIX/t/posix.t 31 1 3.23% 10
+ ../lib/warnings.t 450 1 0.22% 316
+
=head2 OS/390
OS/390 has rather many test failures but the situation is actually
=head2 Failure of Thread tests
-B<Note that support for 5.005-style threading remains experimental.>
+B<Note that support for 5.005-style threading remains experimental
+and practically unsupported.>
The following tests are known to fail due to fundamental problems in
the 5.005 threading implementation. These are not new failures--Perl
5.005_0x has the same bugs, but didn't have these tests.
- lib/autouse.t 4
- t/lib/thr5005.t 19-20
+ ext/List/Util/t/first 2
+ lib/autouse 4
+ ext/Thread/thr5005 19-20
+
+These failures are unlikely to get fixed.
=head2 UNICOS
=head2 VMS
-Rather a lot of tests are failing in VMS, but actually more tests
-succeed in VMS than they used to; it's just that there are many,
-many more tests than there used to be.
-
-Here are the known failures from some compiler/platform combinations.
-
-DEC C V5.3-006 on OpenVMS VAX V6.2
-
- [-.ext.list.util.t]tainted..............FAILED on test 3
- [-.ext.posix]sigaction..................FAILED on test 7
- [-.ext.time.hires]hires.................FAILED on test 14
- [-.lib.file.find]taint..................FAILED on test 17
- [-.lib.math.bigint.t]bigintpm...........FAILED on test 1183
- [-.lib.test.simple.t]exit...............FAILED on test 1
- [.lib]vmsish............................FAILED on test 13
- [.op]sprintf............................FAILED on test 12
- Failed 8/399 tests, 91.23% okay.
-
-DEC C V6.0-001 on OpenVMS Alpha V7.2-1 and
-Compaq C V6.2-008 on OpenVMS Alpha V7.1
-
- [-.ext.list.util.t]tainted..............FAILED on test 3
- [-.lib.file.find]taint..................FAILED on test 17
- [-.lib.test.simple.t]exit...............FAILED on test 1
- [.lib]vmsish............................FAILED on test 13
- Failed 4/399 tests, 92.48% okay.
-
-Compaq C V6.4-005 on OpenVMS Alpha 7.2.1
-
- [-.ext.b]showlex........................FAILED on test 1
- [-.ext.list.util.t]tainted..............FAILED on test 3
- [-.lib.file.find]taint..................FAILED on test 17
- [-.lib.test.simple.t]exit...............FAILED on test 1
- [.lib]vmsish............................FAILED on test 13
- [.op]misc...............................FAILED on test 49
- Failed 6/401 tests, 92.77% okay.
-
+There is one known test failure with a default configuration:
+
+ [.run]switches..........................FAILED on test 1
+
=head2 Win32
In multi-CPU boxes there are some problems with the I/O buffering:
Code like the above is known to leak memory every time the local()
is executed.
+=head2 Localising Tied Arrays and Hashes Is Broken
+
+ local %tied_array;
+
+doesn't work as one would expect: the old value is restored
+incorrectly.
+
=head2 Self-tying of Arrays and Hashes Is Forbidden
Self-tying of arrays and hashes is broken in rather deep and
This limitation will hopefully be fixed in future. (Subroutine
attributes work fine for tieing, see L<Attribute::Handlers>).
+One way to run into this limitation is to have a loop variable with
+attributes within a loop: the tie is called only once, not for each
+iteration of the loop.
+
=head2 Building Extensions Can Fail Because Of Largefiles
Some extensions like mod_perl are known to have issues with
all binaries with different ideas about file offsets, all this is
platform-dependent.
+=head2 Unicode Support on EBCDIC Still Spotty
+
+Though mostly working, Unicode support still has problem spots on
+EBCDIC platforms. One such known spot are the C<\p{}> and C<\P{}>
+regular expression constructs for code points less than 256: the
+pP are testing for Unicode code points, not knowing about EBCDIC.
+
=head2 The Compiler Suite Is Still Experimental
-The compiler suite is slowly getting better but is nowhere near
-working order yet.
+The compiler suite is slowly getting better but it continues to be
+highly experimental. Use in production environments is discouraged.
=head2 The Long Double Support is Still Experimental
projects / p5sagit/p5-mst-13.2.git / blobdiff