The Rust APIs mentioned in the OP support things like pointer tagging without exposing a raw integer address to the user. AIUI CHERI had to bend over backwards to support these operations in C, not because it wanted to but because it had to out of pragmatism. I wager that the CHERI authors would be thrilled if the grandparent's proposal to disallow int2ptr casts were possible to implement without ruling out every significant C codebase in history.
I understand what you’re saying but I think we’re talking about two separate contexts, I’ll call them “CHERI unaware” and “CHERI aware”. There’s plenty of low-level, pointer casting CHERI unaware code, that should continue to work on the hardware. But there’s also people who write secure systems on top of it, and would like to do so in C and C++, so it’s important that they are able to access tags and such. Whether that is through wrappers over assembly instructions, or compiler intrinsics, or whatever, but the easier it is to use from high-level code the more likely it will see adoption there.
