Bridging Swift Error Handling Model to C++

TL;DR

This paper proposes a method to bridge Swift's error handling model with C++, enabling seamless interoperability by allowing Swift errors to be represented as C++ exceptions or result values, enhancing cross-language error management.

Contribution

It introduces a novel approach to integrate Swift's error handling into C++, including exception translation and an alternative mode for non-exception C++ code.

Findings

Enables C++ to throw Swift errors as C++ exceptions.

Supports non-exception C++ code with result-based error handling.

Improves interoperability between Swift and C++ error management.

Abstract

Error handling is the process of responding to and recovering from error conditions in the program. In Swift, errors are represented by values of types that conform to the Error protocol. Throwing an error lets you indicate that something unexpected happened, and the normal flow of execution can't continue. A throw statement is used to throw an error. Optional returns are used to represent the absence of a value, but when an operation fails, it's often useful to understand what caused the failure so that code can respond accordingly. Therefore, I propose to bridge the Swift Error Handling modeling to C++ to improve the interoperability between the programming languages. The main idea is to be able to throw a C++ exception that stores a thrown Swift Error that has to be represented by a C++ class. In addition to that, to support C++ programs that don't use exceptions, I propose an additional interoperability mode for throwing functions. When C++ exceptions are disabled, C++ functions should return a result value that contains either the value returned by the function or the Swift Error value: the Swift::Exception<T> class.