Issue #9624 has been updated by Mika Mannermaa.


Adding a link to a specific commit instead of trunk to prevent further commits from changing the line number: [configure.in:L2707](https://github.com/ruby/ruby/blob/ef0ce95daffe32be9d89f82cce0e4000dbc3fc02/configure.in#L2707)


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Bug #9624: Unrecognized command-line option (CLANG/Xcode 5.1) "-multiply_definedsuppress" prevents installation of gems / ruby on OS X
https://bugs.ruby-lang.org/issues/9624#change-45736

* Author: Mika Mannermaa
* Status: Open
* Priority: Immediate
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.0.0p247 (2013-06-27 revision 41674) [universal.x86_64-darwin13]
* Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN
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Currently there is a single unrecognized command-line option [configure.in:L2707](https://github.com/ruby/ruby/blob/trunk/configure.in#L2707) that should be removed in order for the ruby/gems native extensions to compile on OS X with XCode 5.1 onwards (new CLANG version). The release went live on 11th March 2014, and broke all ruby gems with native extensions.

From [Apple XCode Release Notes](https://developer.apple.com/library/ios/releasenotes/DeveloperTools/RN-Xcode/Introduction/Introduction.html):

> The Apple LLVM compiler in Xcode 5.1 treats unrecognized command-line options as errors. This issue has been seen when building both Python native extensions and Ruby Gems, where some invalid compiler options are currently specified.
> Projects using invalid compiler options will need to be changed to remove those options. To help ease that transition, the compiler will temporarily accept an option to downgrade the error to a warning:
>
> -Wno-error=unused-command-line-argument-hard-error-in-future
>
> Note: This option will not be supported in the future.
> To workaround this issue, set the ARCHFLAGS environment variable to downgrade the error to a warning. For example, you can install a Python native extension with:
> $ ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future easy_install ExtensionName
> 
> Similarly, you can install a Ruby Gem with:
> 
> $ ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future gem install GemName 16214764 updated
>





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