[james412]

C-the-language has no concept of size-tagged arrays at runtime, and I guess it's baked in deeply due to the various guarantees made about sizeof(array), &array[0], and ability to cast &array[0] back to the original array. The iAPX hardware would have gone unused

[pjmlp]

Solaris uses SPARC ADI to great success, iPhone X has pointer validation, and Android 11 has made the work to require ARM MTE in future releases.

[james412]

Pointer tagging is a completely different tech that requires no runtime knowledge of the length of an array