Leopard => Snow Leopard architecture woes with nokogiri / rails - ruby-on-rails

Question

I'm confused. It's a regular state of affairs for me but specifically in this case I felt I could reach out to fellow stackoverflowers (that is, stackoverflow-ers, not stackover-flowers).
uname -a
Darwin macbookpro 10.3.0 Darwin Kernel Version 10.3.0: Fri Feb 26 11:58:09 PST 2010; root:xnu-1504.3.12~1/RELEASE_I386 i386
set
bash-3.2$ set
...
HOSTTYPE=x86_64
...
MACHTYPE=x86_64-apple-darwin10.0
...
I'm having a nightmare rebuilding some native ruby gems and I'm wondering whether this is part of the problem -- part of this machine says its 64 bit but another part 32 ... as far as I can tell?
Under 'About this Mac' it says 'Intel Core 2 Duo' which Apple says is 64 bit. So why, after doing
sudo gem pristine --all
am I still getting this kind of error?
dlopen(/Applications/Rails/ruby/lib/ruby/gems/1.8/gems/nokogiri-1.4.2/lib/nokogiri/nokogiri.bundle, 9): no suitable image found. Did find:
/Applications/Rails/ruby/lib/ruby/gems/1.8/gems/nokogiri-1.4.2/lib/nokogiri/nokogiri.bundle: mach-o, but wrong architecture - /Applications/Rails/ruby/lib/ruby/gems/1.8/gems/nokogiri-1.4.2/lib/nokogiri/nokogiri.bundle
Specifically I had removed nokogiri and reinstalled it. No errors in output.
bash-3.2$ sudo gem install nokogiri
Building native extensions. This could take a while...
Successfully installed nokogiri-1.4.2
1 gem installed
thanks for any thoughts!
UPDATE
I've found a useful post by Chris Noos on a similar problem. This is where I am:
cd /usr/local/lib/ruby/gems/1.8/gems/nokogiri-1.4.2/
then made a file called wem_extconf.rb:
require 'mkmf'
find_library('xml2', 'xmlParseDoc')
dir_config('any-string-here', '/opt/local/include', '/opt/local/lib')
find_library('xml2', 'xmlParseDoc')
Running sudo web_extconf.rb produces
checking for xmlParseDoc() in -lxml2... no
checking for xmlParseDoc() in -lxml2... no
???? But hang on, it is there:
$ port installed | grep libxml2.*active
libxml2 #2.7.7_0+universal (active)
$ ls -l /opt/local/lib | grep libxml2
-rwxr-xr-x 2 root admin 2623276 31 May 20:09 libxml2.2.dylib
-rw-r--r-- 2 root admin 3643928 31 May 20:09 libxml2.a
lrwxr-xr-x 1 root admin 15 31 May 20:09 libxml2.dylib -> libxml2.2.dylib
-rwxr-xr-x 2 root admin 975 31 May 20:09 libxml2.la
And it does appear I have several copies of the thing -- but not sure which one port installed is using (I'm assuming given it's macports, it's /opt?)
$ ls -l /usr/lib | grep libxml2
lrwxr-xr-x 1 root wheel 15 23 May 16:07 libxml2.2.7.3.dylib -> libxml2.2.dylib
-rwxr-xr-x 1 root wheel 3758272 22 Sep 2009 libxml2.2.dylib
lrwxr-xr-x 1 root wheel 15 23 May 16:07 libxml2.dylib -> libxml2.2.dylib
$ ls -l /usr/local/lib | grep libxml2
-rwxr-xr-x 1 root admin 1456292 30 Oct 2009 libxml2.2.dylib
-rw-r--r-- 1 root admin 4812456 30 Oct 2009 libxml2.a
-rwxr-xr-x 1 root admin 1456292 30 Oct 2009 libxml2.dylib
-rwxr-xr-x 1 root admin 951 30 Oct 2009 libxml2.la

Answer 1

On Snow Leopard, gcc has a misleading behavior; even if you are running a i386 kernel, gcc will produce 64 bits binaries by default.
Have you looked at the GEM documentation to see how to specify the targeted architecture ?

Answer 2

Have you installed the XCode Development tools?