错误如下，是因为获取到gem包以后编译不了，因为ff的版本>1.0.9以后，在Windows下面解析有问题。解决办法就是安装1.0.9或以下版本。
C:\Users\Administrator>gem install watir
Temporarily enhancing PATH to include DevKit...
Building native extensions. This could take a while...
ERROR: Error installing watir:
ERROR: Failed to build gem native extension.
Temporarily enhancing PATH to include DevKit...
Building native extensions. This could take a while...
ERROR: Error installing watir:
ERROR: Failed to build gem native extension.
E:/Ruby193_p125/bin/ruby.exe extconf.rb
checking for ffi.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
checking for ffi.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=E:/Ruby193_p125/bin/ruby
--with-ffi_c-dir
--without-ffi_c-dir
--with-ffi_c-include
--without-ffi_c-include=${ffi_c-dir}/include
--with-ffi_c-lib
--without-ffi_c-lib=${ffi_c-dir}/lib
--with-libffi-config
--without-libffi-config
--with-pkg-config
--without-pkg-config
E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to g
enerate an executable file. (RuntimeError)
You have to install development tools first.
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:931:in `block in have_header
'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_fo
r'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in
postpone'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:930:in `have_header'
from extconf.rb:14:in `<main>'
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=E:/Ruby193_p125/bin/ruby
--with-ffi_c-dir
--without-ffi_c-dir
--with-ffi_c-include
--without-ffi_c-include=${ffi_c-dir}/include
--with-ffi_c-lib
--without-ffi_c-lib=${ffi_c-dir}/lib
--with-libffi-config
--without-libffi-config
--with-pkg-config
--without-pkg-config
E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to g
enerate an executable file. (RuntimeError)
You have to install development tools first.
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:931:in `block in have_header
'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_fo
r'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in
postpone'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
from E:/Ruby193_p125/lib/ruby/1.9.1/mkmf.rb:930:in `have_header'
from extconf.rb:14:in `<main>'
Gem files will remain installed in E:/Ruby193_p125/lib/ruby/gems/1.9.1/gems/ffi-
1.4.0 for inspection.
Results logged to E:/Ruby193_p125/lib/ruby/gems/1.9.1/gems/ffi-1.4.0/ext/ffi_c/g
em_make.out
