This Week on perl5-porters (2-8 June 2003)

This Week on perl5-porters (2-8 June 2003)
  What happened this week ? Interesting bugs were found, and solutions
  proposed ; new areas explored, technical points raised, and patches
  applied.

Multiline regexp flag buggy
  Ton Hospel reported bug #22354, about the use of the multiline flag /m
  in regular expressions : when a function is called from the right side
  of a substitution that uses /m, and when this function uses a second
  regular expression, this second regexp has implicitly and incorrectly
  /m turned on.

  Rafael Garcia-Suarez explained what happens behind the scenes : setting
  /m on a match or on a substitution is equivalent to setting the global
  special variable $* to 1 (locally). Thus, it will influence the
  behaviour of all regexps that haven't /m or /s set in that scope.

  As $* is deprecated (and discouraged due to its action-at-distance
  semantics), Rafael proposes to purely and simply remove it. That will
  solve the bug. He asks : when removing a deprecated feature, should the
  deprecation warning be removed as well ?

      http://xrl.us/jb3
      http://xrl.us/jb4

Lexical warnings from XS
  Steve Hays asked how to do the equivalent of warnings::warnif() from XS
  code (conditionally warn, depending on whether a custom warning category
  is in use.) Paul Marquess gives some hints, but says that there is no
  general solution at the moment.

      http://xrl.us/jb5

Temp files
  Should the internal function PerlIO_tempfile() call the core module
  File::Temp ? Jarkko Hietaniemi proposed this. This would avoid code
  duplication and ensure that the core works at the same safety level as
  File::Temp. Gurusamy Sarathy says, however, that this method is bloated
  and should be avoided, especially on Windows, where File::Temp is
  sub-optimal. He proposed an implementation based on the native Win32
  API. Jarkko reverted his changes.

      http://xrl.us/jb6

Fat comma auto-quoting
  William R Ward noticed that the fat comma "=>" no longer auto-quotes
  compound barewords (that contain "::".) Thus, something like

      %h = (Foo::Bar => 1);

  is now refused when "strict 'subs'" is in effect. In fact, only perl
  5.6.1 accepted this last construct without complaining. This is
  potentially dangerous, because if Foo::Bar is a function here, it's not
  turned into a literal string. Rafael and Michael Schwern explored a bit
  more this change, and this ended in a documentation patch, to clarify
  the current behaviour.

      http://xrl.us/jb7

In brief
  Uri Guttman asks about safe signal callbacks -- more precisely, when can
  be a signal callback be invoked, under the new safe signal
  implementation. Nick Ing-Simmons says that perl dispatches signals when
  it gets its next operation. However, the IO system may also dispatch
  them when it gets an "interrupted function call" error (EINTR).

  Dan Kogai proposes that on Mac OS X perl should not be built as a shared
  library by default, to resolve prebinding woes. (Moreover that's the
  default on most other platforms.) Chris Nandor wonders about whether it
  would be useful to use prebinding for XS. Dan doesn't think it's a good
  idea.

  Michael Schwern asked for clarifications about how the "used only once"
  typo warning works, and why it works that way. Rafael explains that it's
  issued only at compile-time, and not for variables defined in modules
  pulled in by "use".

      http://xrl.us/jb8

  Ton Hospel came up with a new bug gem : #22614, "the array length of @-
  and @+ is not properly localized during backtracking", which leads to
  the presence of spurious undefined values in those arrays.

  Steve Hay released Win32::UTCFileTime on CPAN, a module intended to
  provide alternative versions of the built-in functions stat(), lstat()
  and utime() on Win32 systems, to handle correctly UTC file times.

      http://xrl.us/jb9

  Jarkko released a new maintperl snapshot.

About this summary
  This summary was brought to you by your usual summarizer, Rafael
  Garcia-Suarez. Weekly summaries are available on http://use.perl.org/
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  [email protected]. Comments, corrections, additions, and
  suggestions are welcome.