RFC: Target Modifiers

This RFC introduces the concept of "target modifiers," flags that can cause unsoundness if compilation units disagree on them. We propose failing the build if rustc detects disjoint target modifier sets between units, with an escape hatch (-Cunsafe-allow-abi-mismatch) available. This RFC does not stabilize any specific modifiers but establishes the framework for handling them.

You can read the full RFC on the Rust RFCs website.