Question

I have a C++ library for Network communication that I need to port for Mac, previously this library was used on Windows C++ app.

The flow of the C++ Network Lib is based on Exceptions in case of errors, instead of returning error code or last error..

Now since on Mac we use Objective-C/C++ for apps. I need to have UI in Objective-C/C++ but the lib used for the core network functionality is the same C++ lib.

So my question is will the objective C be able to handle exceptions thrown by C++ calls ? if so , how ? if not how do I resolve it ?
Or do we write a wrapper around C++ Lib calls and consume exceptions and return error codes ?

Please advise, how to solve it..

Answer 1

Provided you’re using iOS or the 64-bit runtime on OS X, things pretty much just work. You can write a C++ style try/catch and it will work as expected, as will @try/@catch. Note that you’ll still have the two distinct styles, for Objective-C and C++ exceptions; the only unification is the special case where a catch(...) or @catch(...) catches all exceptions, Objective-C or C++. That’s marginally useful for centralising your clean-up code, but about all you can then do with the exception itself is @throw it blindly again.

But in any case, exceptions shouldn’t be used for flow control in Objective-C (or Objective-C++) programs. You should indeed endeavour to trap the C++ exceptions as they exit the library in question and convert them to a more appropriate mechanism, such as NSError. In particular, avoid letting any of them raise through any Apple or 3rd party frameworks – most such frameworks are not exception safe for Objective-C exceptions, let alone C++ ones, and the consequences are thus undefined (mostly revolving around memory leaks, though many other failures are possible).