ruby-on-rails - rails : can't run app because "An error occured while installing json (1.7.7)"

Question

今天我运行了一个半年前我一直在使用的应用程序，当我运行命令 bundle update 时，我收到了这个错误:

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /Users/adam/.rvm/rubies/ruby-1.9.2-p290/bin/ruby extconf.rb 
creating Makefile

make
/usr/bin/gcc-4.2 -I. -I/Users/adam/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/x86_64-darwin10.8.0 -I/Users/adam/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/ruby/backward -I/Users/adam/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1 -I. -DJSON_GENERATOR -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -O3 -ggdb -Wextra -Wno-unused-parameter -Wno-parentheses -Wpointer-arith -Wwrite-strings -Wno-missing-field-initializers -Wshorten-64-to-32 -Wno-long-long  -fno-common -pipe -O3 -Wall -O0 -ggdb  -o generator.o -c generator.c
make: /usr/bin/gcc-4.2: No such file or directory
make: *** [generator.o] Error 1


Gem files will remain installed in /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/json-1.7.7 for inspection.
Results logged to /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/json-1.7.7/ext/json/ext/generator/gem_make.out
An error occured while installing json (1.7.7), and Bundler cannot continue.
Make sure that `gem install json -v '1.7.7'` succeeds before bundling.

这是来自 Gemfile 的相关部分:

gem "eventmachine", "~> 1.0.0"
gem "json", "~> 1.7.7"

我在 Lion OS X 上运行，我发现这可能有助于更新命令行工具，但我刚刚将其更新到最新版本，但仍然出现此错误。

你能帮我解决这个错误吗？

谢谢

编辑 gem install json -v '1.7.7' 返回:

Building native extensions.  This could take a while...
ERROR:  Error installing json:
    ERROR: Failed to build gem native extension.

        /Users/adam/.rvm/rubies/ruby-1.9.2-p290/bin/ruby extconf.rb
creating Makefile

make
/usr/bin/gcc-4.2 -I. -I/Users/adam/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/x86_64-darwin10.8.0 -I/Users/adam/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/ruby/backward -I/Users/adam/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1 -I. -DJSON_GENERATOR -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -O3 -ggdb -Wextra -Wno-unused-parameter -Wno-parentheses -Wpointer-arith -Wwrite-strings -Wno-missing-field-initializers -Wshorten-64-to-32 -Wno-long-long  -fno-common -pipe -O3 -Wall -O0 -ggdb  -o generator.o -c generator.c
make: /usr/bin/gcc-4.2: No such file or directory
make: *** [generator.o] Error 1


Gem files will remain installed in /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/json-1.7.7 for inspection.
Results logged to /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/json-1.7.7/ext/json/ext/generator/gem_make.out

Answer 1

对于 Xcode 4.x:

sudo ln -s /usr/bin/llvm-gcc-4.2 /usr/bin/gcc-4.2

对于 Xcode 5.x:

export CC=gcc