> It's honestly not that difficult to be rigorous.

Ok, let's try it. I pointed GPT 5.5 at the smallest part of cosmopolitan as I could find in two seconds, net/finger. 299 lines.

describesyn.c:66: q + 13 constructs a pointer that can point well beyond the array plus one element.

C23 6.5.6p9:

> If the pointer operand and the result do not point to elements of the same array object or one past the last element of the array object, the behavior is undefined

Now… you may be trolling, but I do feel like this disproves your assertion. Not you, not me, not Theo de Raadt, can avoid UB.

> the compiler generating code that checks for pointer overflow.

Do you need to check for that specifically? What pointer are you constructing that is not either pointing at a valid object correctly aligned (not UB), or exactly one past the element of an array?

Do you mean for the latter, in case you have an array that ends on the maximum expressible pointer address?

I'm a bit unclear on what you mean by "pointer overflow". From mentioning 56 bit address spaces I'm guessing you mean like the pointer wrapped, not what I pointed to in cosmopolitan, above?

Ok, to be clear that it's not just that one type, if you forgive that one:

net/http/base32.c:64: read sc[0] even if sl=0. I assume this is never called with sl=0, so could be fine.

net/http/ssh.c:355: pointer address underflow? Should that be `e - lp`?

net/http/ssh.c:209/229: double destroy of key. can this code path have non-null members, meaning double free? Looks like it, since line 207 does the parsing and checks that parse worked.

net/http/ssh.c:123: uses memset, which assumes that it sets member variable pointers to NULL (per my post, depending on that means depending on UB), and later these pointers are given to free(), so that's UB.

I won't look deeper into net/http, but presenting just the possibly incorrect remaining comments from jippity:

  - ssh.c:211 and parsecidr.c:44: length-taking APIs use unbounded strstr() / strchr(), so explicit n with non-NUL-terminated input can read beyond the buffer.

  - tokenbucket.c:77 and tokenbucket.c:92: x >> (32 - c) is UB for c == 0 and for out-of-range c.

  - isacceptablehost.c:68: long numeric host labels can overflow signed int b before the function eventually rejects/accepts the host.