I'm well aware.

> If you allocate the memory yourself, the select() system call will work with as many file descriptors as you care to pass to it.

I'm aware of this, as well.

That the kernel interface is more flexible is fine. But the glibc wrapper could sanity-check its arguments.

If you're saying the glibc wrapper also is flexible (assuming one allocs their own fd_sets and … somehow that doesn't run afoul of strict aliasing…?) … and thus, to allow that backbreaking exercise of "you can still use it for all its other bugs" cannot sanity check its arguments (because nfds > the FD set size is permitted) … well … good grief.