If you upgraded to Leopard, you may be getting this nasty error when trying to install Hpricot, which is required by other popular gems such as mechanize..
preston$ sudo gem install mechanize
Password: ********
Bulk updating Gem source index for: http://gems.rubyforge.org
Install required dependency hpricot? [Yn]
Select which gem to install for your platform (i686-darwin8.10.3)
1. hpricot 0.6 (mswin32)
2. hpricot 0.6 (jruby)
3. hpricot 0.6 (ruby)
4. hpricot 0.5 (ruby)
5. hpricot 0.5 (mswin32)
6. Skip this gem
7. Cancel installation
> 3
Building native extensions. This could take a while…
ERROR: While executing gem … (Gem::Installer::ExtensionBuildError)
ERROR: Failed to build gem native extension.ruby extconf.rb install mechanize
checking for main() in -lc… no
creating Makefilemake
gcc -I. -I. -I/opt/local/lib/ruby/1.8/i686-darwin8.10.3 -I. -I/opt/local/include -fno-common -O2 -fno-common -pipe -fno-common -c hpricot_scan.c
cc -dynamic -bundle -undefined suppress -flat_namespace -L/opt/local/lib -L”/opt/local/lib” -o hpricot_scan.bundle hpricot_scan.o -lruby -lpthread -ldl -lobjc
/usr/bin/ld: /usr/lib/gcc/i686-apple-darwin8/4.0.1/../../../libpthread.dylib unknown flags (type) of section 6 (__TEXT,__dof_plockstat) in load command 0
/usr/bin/ld: /usr/lib/gcc/i686-apple-darwin8/4.0.1/../../../libdl.dylib unknown flags (type) of section 6 (__TEXT,__dof_plockstat) in load command 0
/usr/bin/ld: /usr/lib/gcc/i686-apple-darwin8/4.0.1/../../../libobjc.dylib load command 9 unknown cmd field
/usr/bin/ld: /usr/lib/gcc/i686-apple-darwin8/4.0.1/../../../libSystem.dylib unknown flags (type) of section 6 (__TEXT,__dof_plockstat) in load command 0
/usr/bin/ld: /usr/lib/libSystem.B.dylib unknown flags (type) of section 6 (__TEXT,__dof_plockstat) in load command 0
collect2: ld returned 1 exit status
make: *** [hpricot_scan.bundle] Error 1Gem files will remain installed in /opt/local/lib/ruby/gems/1.8/gems/hpricot-0.6 for inspection.
Results logged to /opt/local/lib/ruby/gems/1.8/gems/hpricot-0.6/ext/hpricot_scan/gem_make.out
The issue is that Xcode 3 must be upgraded as well; Hpricot’s native components cannot be built with the older Tiger development tools on Leopard. After installing Xcode 3 from either your Leopard DVD or Apple Developer Connection, run the install again…
preston$ sudo gem install mechanize
Install required dependency hpricot? [Yn] Y
Select which gem to install for your platform (i686-darwin8.10.3)
1. hpricot 0.6 (mswin32)
2. hpricot 0.6 (jruby)
3. hpricot 0.6 (ruby)
4. hpricot 0.5 (ruby)
5. hpricot 0.5 (mswin32)
6. Skip this gem
7. Cancel installation
> 3
Building native extensions. This could take a while…
Successfully installed mechanize-0.6.11
Successfully installed hpricot-0.6
Installing ri documentation for mechanize-0.6.11…
Installing ri documentation for hpricot-0.6…
Installing RDoc documentation for mechanize-0.6.11…
Installing RDoc documentation for hpricot-0.6…
Success!