ちなみに
--pre 付けないと、こんなエラー吐きます。INFO: `gem install -y` is now default and will be removed
INFO: use --ignore-dependencies to install only the gems you list
Building native extensions. This could take a while...
ERROR: Error installing mongrel_cluster:
ERROR: Failed to build gem native extension.
/Users/iwazawa/opt/ruby-1.9.2-p290/bin/ruby extconf.rb
checking for main() in -lc... yes
creating Makefile
make
gcc -I. -I/Users/iwazawa/opt/ruby-1.9.2-p290/include/ruby-1.9.1/x86_64-linux -I/Users/iwazawa/opt/ruby-1.9.2-p290/include/ruby-1.9.1/ruby/backward -I/Users/iwazawa/opt/ruby-1.9.2-p290/include/ruby-1.9.1 -I. -fPIC -O3 -ggdb -Wextra -Wno-unused-parameter -Wno-parentheses -Wpointer-arith -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -o http11.o -c http11.c
http11.c: In function 'http_field':
http11.c:77: error: 'struct RString' has no member named 'ptr'
http11.c:77: error: 'struct RString' has no member named 'len'
http11.c:77: 警告: カンマ演算子の左側の式に効力がありません
http11.c: In function 'header_done':
http11.c:172: error: 'struct RString' has no member named 'ptr'
http11.c:172: error: 'struct RString' has no member named 'ptr'
http11.c:172: error: 'struct RString' has no member named 'ptr'
http11.c:174: error: 'struct RString' has no member named 'ptr'
http11.c:176: error: 'struct RString' has no member named 'ptr'
http11.c:177: error: 'struct RString' has no member named 'len'
http11.c: In function 'HttpParser_execute':
http11.c:298: error: 'struct RString' has no member named 'ptr'
http11.c:299: error: 'struct RString' has no member named 'len'
make: *** [http11.o] エラー 1
Gem files will remain installed in /Users/iwazawa/opt/ruby-1.9.2-p290/lib/ruby/gems/1.9.1/gems/mongrel-1.1.5 for inspection.
Results logged to /Users/iwazawa/opt/ruby-1.9.2-p290/lib/ruby/gems/1.9.1/gems/mongrel-1.1.5/ext/http11/gem_make.out