Performance Impact of Nested Exceptions

Using nested exceptions does introduce some overhead compared to regular exceptions:

1. std::throw_with_nested() dynamically allocates memory to create the nested exception object. This allocation has some time and space overhead.
2. Unwinding nested exceptions requires additional processing. With regular exceptions, the runtime just needs to find the nearest matching catch block. With nested exceptions, it needs to recursively unwind each level of nesting.

However, in most cases this overhead is negligible and is outweighed by the benefits of more expressive error handling. Exceptions should be used for exceptional circumstances anyway, not in performance-critical paths.

If you do find that exception handling is a bottleneck in your code, you can consider techniques like:

• Use non-throwing functions where possible in performance-critical code.
• Catch exceptions by reference to avoid copying.
• Use noexcept to mark functions that don't throw, allowing the compiler to optimize.

But in general, the performance impact of nested exceptions specifically is not something to worry about prematurely. Use them when they make your error handling clearer and more robust.