Ruby项目bundle install时unf_ext 0.0.9原生扩展安装失败求助

在基于以下Gemfile配置的Ruby项目中执行bundle install时遇到编译错误：

ruby '2.3.1'

source 'http://www.rubygems.org'

gem 'aws-flow', '~> 2.4.0'
gem 'aws-sdk-core', '~> 3.65', '>= 3.65.1'
gem 'aws-sdk', '~> 3.0', '>= 3.0.1'
gem 'nokogiri', '~> 1.10.10'
gem 'activerecord', '~> 5.2', '>= 5.2.3'
gem 'sqlite3', '~> 1.3', '= 1.3.9'
gem 'rubyzip', '~> 1.2', '>= 1.2.3'
gem 'mechanize', '~> 2.7', '>= 2.7.5'
gem 'slack-notifier', '~> 1.5', '>= 1.5.1'
gem 'minitest', '~> 5.8.4'
gem 'connection_pool', '~> 2.2.5'
gem 'httparty', '~> 0.19.1'
gem 'webrick', '~> 1.7.0'
gem 'net-http-persistent', '= 4.0.1'

错误发生在安装unf_ext（版本0.0.9）这个依赖gem时，具体报错信息如下：

Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as root will break this application for all non-root users on this machine.
Fetching gem metadata from http://www.rubygems.org/
Fetching version metadata from http://www.rubygems.org/
Fetching dependency metadata from http://www.rubygems.org/
Resolving dependencies..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Using concurrent-ruby 1.2.2
Using minitest 5.8.5
Using thread_safe 0.3.6
Using arel 9.0.0
Using aws-eventstream 1.2.0
Using json 1.8.6
Using mini_portile2 2.4.0
Using lru_redux 0.8.4
Using aws-partitions 1.848.0
Using jmespath 1.6.2
Using aws-sigv2 1.1.0
Using connection_pool 2.2.5
Installing unf_ext 0.0.9 with native extensions

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /opt/rubies/ruby-2.3.1/lib/ruby/gems/2.3.0/gems/unf_ext-0.0.9/ext/unf_ext
/opt/rubies/ruby-2.3.1/bin/ruby -r ./siteconf20231113-2866-7e5i1z.rb extconf.rb
checking for main() in -lstdc++... yes
creating Makefile

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /opt/rubies/ruby-2.3.1/lib/ruby/gems/2.3.0/extensions/x86_64-linux/2.3.0-static/unf_ext-0.0.9/mkmf.log

current directory: /opt/rubies/ruby-2.3.1/lib/ruby/gems/2.3.0/gems/unf_ext-0.0.9/ext/unf_ext
make "DESTDIR=" clean

current directory: /opt/rubies/ruby-2.3.1/lib/ruby/gems/2.3.0/gems/unf_ext-0.0.9/ext/unf_ext
make "DESTDIR="
compiling unf.cc
cc1plus: warning: command line option ‘-Wdeclaration-after-statement’ is valid for C/ObjC but not for C++ [enabled by default]
cc1plus: warning: command line option ‘-Wimplicit-function-declaration’ is valid for C/ObjC but not for C++ [enabled by default]
unf.cc:39:3: sorry, unimplemented: non-trivial designated initializers not supported
   };
   ^
unf.cc:39:3: sorry, unimplemented: non-trivial designated initializers not supported
make: *** [unf.o] Error 1

make failed, exit code 2

Gem files will remain installed in /opt/rubies/ruby-2.3.1/lib/ruby/gems/2.3.0/gems/unf_ext-0.0.9 for inspection.
Results logged to /opt/rubies/ruby-2.3.1/lib/ruby/gems/2.3.0/extensions/x86_64-linux/2.3.0-static/unf_ext-0.0.9/gem_make.out
Using mime-types-data 3.2023.1003
Using multi_xml 0.6.0
Using net-http-digest_auth 1.4.1
Using ntlm-http 0.1.1
Using webrick 1.7.0
Using webrobots 0.1.2
Using rubyzip 1.3.0
Using slack-notifier 1.5.1
Using sqlite3 1.3.9
Using bundler 1.12.1
Using i18n 1.14.1
Using tzinfo 1.2.11
Using aws-sigv4 1.6.1
Using nokogiri 1.10.10
Using net-http-persistent 4.0.1
An error occurred while installing unf_ext (0.0.9), and Bundler cannot continue.
Make sure that `gem install unf_ext -v '0.0.9'` succeeds before bundling.

未在Gemfile中显式引入unf_ext，它是其他gem的依赖，查看mkmf.log后仍无法定位问题，需要解决编译错误并确认是否需要调整gem版本。

1. 定位unf_ext的依赖来源 #

执行以下命令可以追踪到哪个gem引入了unf_ext：

# 查看依赖树中unf_ext的关联
bundle list --tree | grep -B2 -A2 unf_ext

通常unf_ext是unf的依赖，而unf又被mechanize这类处理网页编码的gem引入，你的Gemfile里的mechanize (~>2.7.5)大概率是源头。

2. 解决编译错误 #

编译报错non-trivial designated initializers not supported的核心原因是：Ruby 2.3.1版本过于老旧，搭配的unf_ext 0.0.9代码与当前系统的高版本C++编译器不兼容。

可选修复方案： #

• 方案一：锁定兼容的unf_ext版本
  在Gemfile中添加显式版本锁定，选择适配Ruby 2.3.1和旧编译器的版本，比如unf_ext 0.0.7.7：

gem 'unf_ext', '0.0.7.7'

之后重新执行bundle install。

• 方案二：临时指定低版本编译器
  如果是Linux环境，安装GCC 6或更低版本并临时指定编译器：

# Debian/Ubuntu系统安装低版本编译器
sudo apt install gcc-6 g++-6
# 用指定编译器执行bundle install
CC=gcc-6 CXX=g++-6 bundle install

• 方案三：升级Ruby版本（长期推荐）
  Ruby 2.3.1已停止维护多年，存在安全漏洞，建议升级到2.7.x或更高的维护版本，同时调整Gemfile中相关gem的版本到兼容范围，从根本上解决依赖兼容性问题。例如：

ruby '2.7.8'
# 调整相关gem版本，比如mechanize升级到~>2.8.5，aws-sdk适配新版本Ruby

3. 验证修复 #

执行bundle install后，若所有gem安装成功，运行项目测试功能是否正常。

内容的提问来源于stack exchange，提问作者user15980977