diff options
Diffstat (limited to 'pod/perldelta.pod')
| -rw-r--r-- | pod/perldelta.pod | 95 |
1 files changed, 63 insertions, 32 deletions
diff --git a/pod/perldelta.pod b/pod/perldelta.pod index 734e940b42..cf6036ff02 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -27,12 +27,17 @@ might have symbol conflicts if you embed Perl in another application, just as in the 5.003 release. By default, binary compatibility is preserved at the expense of symbol table pollution. -=head2 New Opcode Module and Revised Safe Module +=head2 Subroutine Parameters Are Not Autovivified -A new Opcode module supports the creation, manipulation and -application of opcode masks. The revised Safe module has a new API -and is implemented using the new Opcode module. Please read the new -Opcode and Safe documentation. +In Perl versions 5.002 and 5.003, array and hash elements used as +subroutine parameters were "autovivified"; that is, they were brought +into existence if they did not already exist. For example, calling +C<func($h{foo})> would create C<$h{foo}> if it did not already exist, +causing C<exists $h{foo}> to become true and C<keys %h> to return +C<('foo')>. + +Perl 5.004 returns to the pre-5.002 behavior of I<not> autovivifying +array and hash elements used as subroutine parameters. =head2 Fixed Parsing of $$<digit>, &$<digit>, etc. @@ -52,6 +57,13 @@ previously-working script to now fail -- which should be construed as a blessing, since that indicates a potentially-serious security hole was just plugged. +=head2 New Opcode Module and Revised Safe Module + +A new Opcode module supports the creation, manipulation and +application of opcode masks. The revised Safe module has a new API +and is implemented using the new Opcode module. Please read the new +Opcode and Safe documentation. + =head2 Internal Change: FileHandle Class Based on IO::* Classes File handles are now stored internally as type IO::Handle. The @@ -222,7 +234,7 @@ would yield the same sequence of random numbers on most or all machines. Now, when perl sees that you're calling C<rand> and haven't yet called C<srand>, it calls C<srand> with the default seed. You should still call C<srand> manually if your code might ever be run on a pre-5.004 system, -of course, or if you want a seed other than the default. +of course, or if you want a seed other than the default. =item $_ as Default @@ -241,8 +253,8 @@ zero-width assertion. See L<perlop> and L<perlre>. =item nested C<sub{}> closures work now -Prior to the 5.004 release, nested anonymous functions -didn't work right. They do now. +Prior to the 5.004 release, nested anonymous functions didn't work +right. They do now. =item formats work right on changing lexicals @@ -258,7 +270,7 @@ before, and is fine now: $i . write; - } + } =back @@ -324,9 +336,9 @@ This is the constructor for the class. That means it is expected to return an object of some sort. The reference can be used to hold some internal information. - sub TIEHANDLE { - print "<shout>\n"; - my $i; + sub TIEHANDLE { + print "<shout>\n"; + my $i; return bless \$i, shift; } @@ -336,29 +348,46 @@ This method will be triggered every time the tied handle is printed to. Beyond its self reference it also expects the list that was passed to the print function. - sub PRINT { - $r = shift; - $$r++; + sub PRINT { + $r = shift; + $$r++; return print join( $, => map {uc} @_), $\; } +=item READ this LIST + +This method will be called when the handle is read from via the C<read> +or C<sysread> functions. + + sub READ { + $r = shift; + my($buf,$len,$offset) = @_; + print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset"; + } + =item READLINE this This method will be called when the handle is read from. The method should return undef when there is no more data. - sub READLINE { - $r = shift; - return "PRINT called $$r times\n"; + sub READLINE { + $r = shift; + return "PRINT called $$r times\n" } +=item GETC this + +This method will be called when the C<getc> function is called. + + sub GETC { print "Don't GETC, Get Perl"; return "a"; } + =item DESTROY this As with the other types of ties, this method will be called when the tied handle is about to be destroyed. This is useful for debugging and possibly for cleaning up. - sub DESTROY { + sub DESTROY { print "</shout>\n"; } @@ -366,8 +395,15 @@ possibly for cleaning up. =head2 Malloc Enhancements -If perl's malloc() is used, you can print memory statistics at runtime -by running Perl thusly: +Four new compilation flags are recognized by malloc.c. (They have no +effect if perl is compiled with system malloc().) + +=over + +=item -DDEBUGGING_MSTATS + +If perl is compiled with C<DEBUGGING_MSTATS> defined, you can print +memory statistics at runtime by running Perl thusly: env PERL_DEBUG_MSTATS=2 perl your_script_here @@ -376,11 +412,6 @@ exit; with a value of 1, the statistics ares printed only on exit. (If you want the statistics at an arbitrary time, you'll need to install the optional module Devel::Peek.) -In addition, three new compilation flags are recognized by malloc.c. -(They have no effect if perl is compiled with system malloc().) - -=over - =item -DEMERGENCY_SBRK If this macro is defined, running out of memory need not be a fatal @@ -498,7 +529,7 @@ New constants in the existing Fcntl modules are now supported, provided that your operating system happens to support them: F_GETOWN F_SETOWN - O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC + O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC O_EXLOCK O_SHLOCK These constants are intended for use with the Perl operators sysopen() @@ -747,7 +778,7 @@ Although not new, this has been massively updated. Several new conditions will trigger warnings that were silent before. Some only affect certain platforms. -The following new warnings and errors outline these. +The following new warnings and errors outline these. These messages are classified as follows (listed in increasing order of desperation): @@ -906,7 +937,7 @@ used.) You probably wrote something like this: - @list = qw( + @list = qw( a # a comment b # another comment ); @@ -914,7 +945,7 @@ You probably wrote something like this: when you should have written this: @list = qw( - a + a b ); @@ -933,7 +964,7 @@ aren't needed to separate the items. (You may have used different delimiters than the parentheses shown here; braces are also frequently used.) -You probably wrote something like this: +You probably wrote something like this: qw! a, b, c !; @@ -1077,4 +1108,4 @@ Constructed by Tom Christiansen, grabbing material with permission from innumerable contributors, with kibitzing by more than a few Perl porters. -Last update: Tue Jan 14 14:03:02 EST 1997 +Last update: Sat Mar 8 19:51:26 EST 1997 |