title: Unable to gem install breakpoint on Mac
body: <p>I am trying to install breakpoint on my macbook but it fails to compile. The full output is below. I am new to Mac and am not sure what I might have done wrong. My Windows workstation had no trouble this evening.</p>
  
  <p>Thank you!</p>
  
  <pre><code>Aarons-MacBook-Pro:~ aarongreenlee$ sudo gem install breakpoint
  Password:
  Building native extensions.  This could take a while...
  ERROR:  Error installing breakpoint:
      ERROR: Failed to build gem native extension.
  
      /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
  checking for ffi.h... no
  checking for ffi.h in /usr/local/include,/usr/include/ffi... yes
  checking for ffi_call() in -lffi... yes
  checking for ffi_prep_closure()... yes
  checking for ffi_raw_call()... no
  checking for rb_thread_blocking_region()... yes
  checking for rb_thread_call_with_gvl()... yes
  checking for rb_thread_call_without_gvl()... yes
  checking for ffi_prep_cif_var()... no
  creating extconf.h
  creating Makefile
  
  make "DESTDIR="
  compiling AbstractMemory.c
  compiling ArrayType.c
  compiling Buffer.c
  compiling Call.c
  Call.c:303:5: warning: implicit declaration of function 'rb_thread_call_without_gvl' is invalid in C99 [-Wimplicit-function-declaration]
      rbffi_thread_blocking_region(call_blocking_function, data, (void *) -1, NULL);
      ^
  ./Thread.h:78:39: note: expanded from macro 'rbffi_thread_blocking_region'
  # define rbffi_thread_blocking_region rb_thread_call_without_gvl
                                        ^
  1 warning generated.
  compiling ClosurePool.c
  compiling DataConverter.c
  DataConverter.c:43:1: warning: control may reach end of non-void function [-Wreturn-type]
  }
  ^
  1 warning generated.
  compiling DynamicLibrary.c
  compiling ffi.c
  compiling Function.c
  Function.c:479:33: warning: incompatible pointer types passing 'VALUE (void *)' to parameter of type 'void *(*)(void *)' [-Wincompatible-pointer-types]
          rb_thread_call_with_gvl(callback_with_gvl, &amp;cb);
                                  ^~~~~~~~~~~~~~~~~
  Function.c:102:46: note: passing argument to parameter 'func' here
  extern void *rb_thread_call_with_gvl(void *(*func)(void *), void *data1);
                                               ^
  Function.c:563:9: warning: implicit declaration of function 'rb_thread_call_without_gvl' is invalid in C99 [-Wimplicit-function-declaration]
          rb_thread_call_without_gvl(async_cb_wait, &amp;w, async_cb_stop, &amp;w);
          ^
  Function.c:738:1: warning: control reaches end of non-void function [-Wreturn-type]
  }
  ^
  3 warnings generated.
  compiling FunctionInfo.c
  compiling LastError.c
  compiling LongDouble.c
  compiling MappedType.c
  compiling MemoryPointer.c
  compiling MethodHandle.c
  compiling Platform.c
  compiling Pointer.c
  compiling Struct.c
  compiling StructByReference.c
  compiling StructByValue.c
  compiling StructLayout.c
  compiling Thread.c
  compiling Type.c
  compiling Types.c
  compiling Variadic.c
  linking shared-object ffi_c.bundle
  clang: error: unknown argument: '-multiply_definedsuppress' [-Wunused-command-line-argument-hard-error-in-future]
  clang: note: this will be a hard error (cannot be downgraded to a warning) in the future
  make: *** [ffi_c.bundle] Error 1
  
  
  Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/ffi-1.9.3 for inspection.
  Results logged to /Library/Ruby/Gems/2.0.0/gems/ffi-1.9.3/ext/ffi_c/gem_make.out
  Aarons-MacBook-Pro:~ aarongreenlee$ ls -l
  total 38632
  -rw-r--r--@  1 aarongreenlee  staff        11 Mar 14 09:22 22650.txt
  -rw-r--r--@  1 aarongreenlee  staff  19771836 Mar 18 10:02 22659.mp4
  drwxr--r--   3 aarongreenlee  staff       102 Feb 22 10:45 ABBYY
  drwxr-xr-x   2 aarongreenlee  staff        68 Mar 23 14:12 Applications
  drwx------@  3 aarongreenlee  staff       102 Nov 18 22:12 Creative Cloud Files
  drwx------+ 13 aarongreenlee  staff       442 Mar 25 22:07 Desktop
  drwx------+ 27 aarongreenlee  staff       918 Mar 21 14:16 Documents
  drwx------+ 55 aarongreenlee  staff      1870 Mar 19 22:48 Downloads
  drwx------@ 31 aarongreenlee  staff      1054 Mar  4 09:36 Google Drive
  drwx------@ 53 aarongreenlee  staff      1802 Jan  6 23:15 Library
  drwx------+  8 aarongreenlee  staff       272 Mar 22 22:33 Movies
  drwx------+  4 aarongreenlee  staff       136 Nov 14 10:10 Music
  drwx------+  5 aarongreenlee  staff       170 Mar 19 18:07 Pictures
  drwxr-xr-x+  5 aarongreenlee  staff       170 Nov  1 22:35 Public
  drwxr-xr-x   5 root           staff       170 Nov 11 18:43 logs
  drwxr-xr-x   3 aarongreenlee  staff       102 Jan 12 14:50 pkg
  drwxr-xr-x   3 aarongreenlee  staff       102 Jan 12 14:50 src
  drwxr-xr-x   2 root           staff        68 Feb  2 12:11 tmp
  Aarons-MacBook-Pro:~ aarongreenlee$ cd ~/Documents/Development/golang/src/git.knowboth.com/errorchomp/
  Aarons-MacBook-Pro:errorchomp aarongreenlee$ compass compile
  LoadError on line ["45"] of /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb: cannot load such file -- breakpoint
  Run with --trace to see the full backtrace
  Aarons-MacBook-Pro:errorchomp aarongreenlee$ exit
  logout
  </code></pre>