From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-09-17T00:09:23+09:00
Subject: Re: bug in require?

On Fri, 16 Sep 2005, Han Holl wrote:

> On 9/16/05, Yukihiro Matsumoto <matz@ruby-lang.org> wrote:
>>
>> Hi,
>>
>> In message "Re: bug in require?"
>> on Fri, 16 Sep 2005 20:56:38 +0900, Han Holl <han.holl@gmail.com> writes:
>>
>> |Yes, that's answering where it happens.
>> |Remains the question why.
>>
>> It was the easiest way to check if a file is loadable (i.e. a file
>> exists and has proper permissions). Maybe it's possible to replace it
>> with access(3).
>>
>> matz.
>>
>> Ara's question was what the difference was between execution from the
> commandline and from a script.  Only now I see that the difference is that
> from the commandline he requires "digest/md5.so", and from the file
> 'digest/md5', without the extension.  Which means that you get a
> considerable perfomance penalty by omitting the extension. In a
> gem-installed rails environment the seachpath can easily be 25 directories.
> Multiple requires withou extension can be costly there.


right.  try this fix for your rails app:

   harp:~ > strace ruby -e'4.times{ require "digest/md5" }' 2>&1 |egrep 'open.*md5'
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3


   harp:~ > strace ruby -r ./require.rb -e'4.times{ require "digest/md5" }' 2>&1 |egrep 'open.*md5'
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3
   open("/usr/lib/ruby/1.6/i386-linux-gnu/digest/md5.so", O_RDONLY) = 3


   harp:~ > cat ./require.rb
   require 'rbconfig.rb'
   module Kernel
     alias_method '__require__', 'require'
     def require lib
       if((ext = lib[ %r/\.[^\.]+$/ ]))
         __require__ lib
       else
         dlext, dlext2 = ::Config::CONFIG['DLEXT'], ::Config::CONFIG['DLEXT2']
         __require__ "#{ lib }.#{ dlext }" rescue
         __require__ "#{ lib }.#{ dlext2 }" rescue
         __require__ "#{ lib }.rb"
       end
     end
   end


cheers.

-a
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