Carbon and C++ Interoperability: Memory Safety Boundaries for Legacy Pointers

Carbon aims to provide a bidirectional bridge with C++ while maintaining a memory safety model through its default 'safe' dialect. This model restricts pointer arithmetic and unchecked memory access to prevent common vulnerabilities found in manual memory management.

When integrating Carbon with legacy C++ code, the language must reconcile its strict type system with C++'s manual memory management. A specific challenge arises at the boundary where Carbon references objects managed by C++ pointers, particularly when determining which operations necessitate a transition from a safe context to an unsafe block.

Given the evolving specification of the Carbon language, there is uncertainty regarding the precise rules for pointer validation during this interoperability process.

• What are the definitive criteria for designating a C++ pointer interaction as 'unsafe' within a Carbon module?
• How does the compiler enforce memory safety when a Carbon reference points to a C++ object with an indeterminate lifetime?