CHERI is effectively a mix of option a and b in my categorization, necessitating hardware changes and ABI changes and limited amounts of software changes. I'm n

CHERI is effectively a mix of option a and b in my categorization, necessitating hardware changes and ABI changes and limited amounts of software changes. I'm not familiar with the other options in particular, but they likely rely on a mix of ABI changes and/or software changes given the general history of such "let's fix C" proposals. ABI breaks are not a real solution to the problem. When you talk about changing the ABI of a basic pointer type, this requires a flag day change of literally all the software on the computer at once, which has not been feasible for decades. This isn't an excuse; it's the cold hard reality of C/C++ development. There is no solution that doesn't require some amount of software change. And the C committee is looking at fixing it! That's why C23 makes support for variably-modified types mandatory--it's the first step towards getting working compiler-generated bounds checks without changing the ABI and with relatively minimal software change (just tweak the function prototype a little bit).