see:

http://developer.apple.com/documentation/ReleaseNotes/Cocoa/Objective-C++.html

This describes the restrictions which apply to the mixing of ObjectiveCee and CeePlusPlus.

MacOsx 10.1 introduces the Objective-C++ front-end to the Mac OS X version of gcc. Objective-C++ allows you to mix CeePlusPlus and ObjectiveCee code in the same source source file. Using Objective-C++, you can directly call Objective-C objects from C++ code, and you can directly call C++ code from Objective-C objects. Thus, Objective-C++ allows you to use C++ class libraries directly from within your Cocoa application, or to use Cocoa or Foundation objects directly from within your C++ application.

ObjectiveCeePlusPlus is available for use as part of the GnuCompilerCollection on systems other than the MacOsx.

There is not much point in using this without an object oriented framework. GnuStep provides this for non-Macintosh systems. 
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see: ObjectiveCee GnuCpp CeeCeePlusPlus
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CategoryProgrammingLanguage CategoryCee CategoryCpp