In OSX 10.10 Yosemite the

/usr/include/dispatch/object.h

header file contains code that can be processed by clang but not GCC. The specific error that GCC 4.9 (via homebrew) produces is:

/usr/include/dispatch/object.h:143:15: error: expected unqualified-id before '^' token
 typedef void (^dispatch_block_t)(void);
               ^
/usr/include/dispatch/object.h:143:15: error: expected ')' before '^' token
/usr/include/dispatch/object.h:362:3: error: 'dispatch_block_t' has not been declared
   dispatch_block_t notification_block);
   ^

The fix:

//Change
typedef void (^dispatch_block_t)(void);
//To
typedef void* dispatch_block_t;

Similarly if using Xcode, the file is located at:

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include/dispatch/object.h dispatch/object.h

Reference

https://github.com/andrewgho/movewin-ruby/issues/1