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Re: [PATCH 2/5] gitweb: Do not use bareword filehandles

From
Jakub Narebski <jnareb@gmail.com>
Date
May 10, 2009, 09:27 UTC
Message-ID
<200905101127.51963.jnareb@gmail.com>
In-Reply-To
<20090510075053.GA6058@machine.or.cz>
On Sun, 10 May 2009, Petr Baudis wrote:
> On Sun, May 10, 2009 at 02:36:19AM +0200, Jakub Narebski wrote:
Show 26 quoted lines
> > ---
> > Perl::Critic::Policy::InputOutput::ProhibitBarewordFileHandles
> > 
> >   Write open my $fh, q{<}, $filename; instead of open FH, q{<}, $filename;.
> > 
> >   Using bareword symbols to refer to file handles is particularly evil
> >   because they are global, and you have no idea if that symbol already
> >   points to some other file handle. You can mitigate some of that risk by
> >   'local'izing the symbol first, but that's pretty ugly. Since Perl 5.6, you
> >   can use an undefined scalar variable as a lexical reference to an
> >   anonymous filehandle.
> > 
> > See also Damian Conway's book "Perl Best Practices",
> > chapter "10.1. Filehandles" (Don't use bareword filehandles.)
> > 
> > 
> > This follows similar patch for git-send-email.perl by Bill Pemberton
> > http://permalink.gmane.org/gmane.comp.version-control.git/117886
> > 
> > CC-ed Pasky, who is responsible for code in both cases...
> 
> Yeah, the book I learnt Perl from many years ago used bareword
> filehandles (but it was an excellent textbook in most other aspects)
> so this is a custom I have to work hard to evict. ;-)
> 
> Acked-by: Petr Baudis <pasky@suse.cz>

Well, on one hand this is less of an issue for standalone script like gitweb is than for library / module. On the other hand we use indirect filehandles everywhere else, so it is also matter of style consistency.

"Perl Best Practices" gives as an example of bad behavior which we can get by using bareword [global] filehandles: 1) automatic closing of other filehandle with the same name (e.g. not only you use FILE for bareword filehandle); 2) open might fail if there exist subroutine / constant with the same name as filehandle e.g. EXDEV (from POSIX module).

Note however that prior to Perl 5.6 it was not that easy to avoid using bareword filehandles. Perhaps the book in question (or author of the textbook you mention) started with earlier Perl...

P.S. Git.pm generates surprisingly small amount of perlcritic-isms, most of whose are either matter of style, or are false positives.

-- 
Jakub Narebski
Poland
Previous: Petr BaudisNext: Jakub Narebski
Message 6 of 16 in “gitweb: Some code cleanups (up to perlcritic --stern)”
  1. 0/5 gitweb: Some code cleanups (up to perlcritic --stern)Jakub Narebski, May 10, 2009
  2. 1/5 gitweb: Remove function prototypesJakub Narebski, May 10, 2009
  3. Jakub NarebskiMay 10, 2009
  4. 2/5 gitweb: Do not use bareword filehandlesJakub Narebski, May 10, 2009
  5. Petr BaudisMay 10, 2009
  6. Jakub NarebskiMay 10, 2009
  7. 2/5 gitweb: Do not use bareword filehandlesJakub Narebski, May 11, 2009
  8. 3/5 gitweb: Always use three argument form of openJakub Narebski, May 10, 2009
  9. 3/5 gitweb: Always use three argument form of openJakub Narebski, May 11, 2009
  10. 4/5 gitweb: Localize magic variable $/Jakub Narebski, May 10, 2009
  11. 5/5 gitweb: Use block form of map/grep in a few cases moreJakub Narebski, May 10, 2009
  12. Junio C HamanoMay 11, 2009
  13. Jakub NarebskiMay 11, 2009
  14. Junio C HamanoMay 11, 2009
  15. Daniel PittmanMay 11, 2009
  16. Jakub NarebskiMay 11, 2009

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