On Tue, Jan 13, 2026 at 11:40:55PM +0100, Florian Weimer wrote:

In <linux/mount.h>, we have this:

#define OPEN_TREE_CLOEXEC      O_CLOEXEC       /* Close the file on execve() */

This causes a few pain points for us to on the glibc side when we mirror
this into <linux/mount.h> becuse O_CLOEXEC is defined in <fcntl.h>,
which is one of the headers that's completely incompatible with the UAPI
headers.

The reason why this is painful is because O_CLOEXEC has at least three
different values across architectures: 0x80000, 0x200000, 0x400000

Even for the UAPI this isn't ideal because it effectively burns three
open_tree flags, unless the flags are made architecture-specific, too.

I think that just got cargo-culted... A long time ago some API define as
O_CLOEXEC and now a lot of APIs have done the same. I'm pretty sure we
can't change that now but we can document that this shouldn't be ifdefed
and instead be a separate per-syscall bit. But I think that's the best
we can do right now.