Re: [kernel patch] fcntl(...) to close many descriptors

[Garrett Wollman]

<<On Mon, 29 Jan 2001 11:26:29 -0800 (PST), Luigi Rizzo <[EMAIL PROTECTED]> said:

> but there is a problem with syscall() in that according to
> the manpages it cannot handle in/out parameters as instead
> it is supported by ioctl/fcntl

Of course it can, and the manual page doesn't even suggest what you
say.  It says:

     There is no way to simulate system calls that have multiple return values
     such as pipe(2).

pipe(2) is a special case in that it returns two values rather than
one.  The actual pipe(2) system call has *no* formal parameters; the
unpacking of the two values returned into the declared C formal
parameter is done by an assembly-language stub.  (This was done for
reasons of speed; it is much faster to return two values than it is to
copyout() a two-element array.

If you were implementing a Lisp binding of POSIX, you would probably
define PIPE to be a niladic function which returns a list of two
descriptors.

-GAWollman



To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-hackers" in the body of the message