[lkml]   [2012]   [Feb]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 21/21] posix_types: Remove fd_set macros
On 02/14/2012 11:18 AM, David Howells wrote:
> Tony Luck <> wrote:
>> Adding a #include <linux/string.h> to include/linux/time.h fixes them for me.
> Which is one of the reasons I'd rather not see these things cropping up in
> linux/time.h. Either put them in linux/select.h (mirroring userspace) or
> stick them in linux/poll.h with the rest of the polling paraphernalia.
> __FD_SET() and co aren't exported to userspace anyway, as I understand it, so
> it shouldn't hurt to bung them in linux/poll.h, and if they are exported to
> userspace, they should stay in posix_types.h, shouldn't they?
> To support this, at least three #includes will have to be added to
> linux/time.h: linux/posix_types.h (which is fair enough), linux/bitops.h and
> linux/string.h.

We can do that, but we'd almost certainly have to #include
<linux/select.h> in <linux/time.h>. The following macros are defined in
<linux/time.h> and *exported to userspace*:


#define FD_SET(fd,fdsetp) __FD_SET(fd,fdsetp)
#define FD_CLR(fd,fdsetp) __FD_CLR(fd,fdsetp)
#define FD_ISSET(fd,fdsetp) __FD_ISSET(fd,fdsetp)
#define FD_ZERO(fdsetp) __FD_ZERO(fdsetp)

Now, this largely mimics what has happened in userspace over time; to
quote POSIX:

The <sys/time.h> header shall define the fd_set type as described in

The <sys/time.h> header shall define the following as described in


Inclusion of the <sys/time.h> header may make visible all symbols from
the <sys/select.h> header.

Cleaning up <linux/time.h> would indeed be a worthwhile goal -- it's not
clear to me that it can safely be used to build a POSIX-compliant
userspace. In particular, it mixes the functions of <sys/time.h> and
<time.h>, but <time.h> symbols are not permitted to leak into
<sys/time.h> space as far as I read the specification. However, this
feels like a slightly orthogonal task (in fact, it might belong more in
your uabi work.)

H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

 \ /
  Last update: 2012-02-14 20:47    [W:0.065 / U:0.688 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site