stream_buffer_init() calls malloc directly, so it's not protected by safe_malloc(). (Unless there is some funky re-define stuff I didn't see).

%x takes unsigned int, not a char. (Although I guess you could just rely on promotion here if you can rely on the unsignedness of char).

> Could you point out a line that is prone to integer overflows?

Never said that it was an overflow (just C&P that comment from the file). Just said its invalid use. Which I'm totally willing to agree on the compiler mostly getting correct behavior. Just not really something I'd want to see landing in something that we all need a really good, secure implementation of.

Best of luck though, I hope you iterate on this to the point we can have a really good DNS implementation in C, in user-space, with optional async processing.