On Mon, Sep 06, 2021 at 02:24:39PM -0700, Linus Torvalds wrote:

There are some *very* core header files that the kernel cannot include
from outside. That "stdlib.h" thing already came up in the errors I
quoted.

But I think you'll find that you guys want to include things like
<errno.h> too, and you'll probably add others (<types.h>? things like
that) simply because they always work fine in user space, and you'd
not even notice.

Guess what.  We actually test this.  We do notice.  Except we don't,
because all those problems do not actually exist.

Long ago there were issues.  We do not live long ago now.

I'm pretty sure you guys don't really want to deal with the pain that
is crazy kernel people that have their very bare environment.

There are many other users that use freestanding environments.  Most of
them do use the standard headers.

So you may *think* you want the kernel to use your header files
"because compiler portability". Instead, you should be very thankful
that we don't, and that you don't have to deal with our mess any more
than you already do.

We would like it to be *less* pain, *less* unnecessary work, that is why
we would like the kernel to use the compiler headers.  Instead of what
the current patches do: getting rid of more of them, which will end up
as more work for everyone.


Segher