The behavior that Cosmopolitan needs is required by POSIX because UNIX Sixth Edition didn't have shebang lines. It's normally an implementation detail of execve() in C libraries and the behavior is implemented by nearly all shells too. So far the only issue has been that some shells, like zsh, have a binary safety check where it refuses to run scripts that have embedded NUL characters. I worked with the FreeBSD team to get POSIX revised to clarify the correct behavior w.r.t. these restrictions. FreeBSD's /bin/sh has already been patched and zsh is pending upstream. https://github.com/jart/zsh/commit/94a4bc14bb2e415ec3d10cf71...
I appreciate the thoroughness with which you are pursuing this. The amount of work you're doing outside of the technical aspect is definitely something I can admit that I would've never pursued. It's encouraging to see.
