Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add CLONE_PIDFD]

[Linus Torvalds]

On Mon, Apr 29, 2019 at 1:38 PM Florian Weimer <fweimer@xxxxxxxxxx> wrote:
>
> In Linux-as-the-ABI (as opposed to Linux-as-the-implementation), vfork
> is sometimes implemented as fork, so applications cannot rely on the
> vfork behavior regarding the stopped parent and the shared address
> space.

What broken library does that?

Sure, we didn't have a proper vfork() long long long ago. But that
predates both git and BK, so it's some time in the 90's. We've had a
proper vfork() *forever*.

> In fact, it would be nice to have a flag we can check in the posix_spawn
> implementation, so that we can support vfork-as-fork without any run
> time cost to native Linux.

No. Just make a bug-report to whatever broken library you use. What's
the point of having a library that can't even get vfork() right? Why
would you want to have a flag to say "vfork is broken"?

                 Linus