Re: POLLRDNORM in poll()

[Jonathan Wakely <cow at compsoc dot man dot ac dot uk>]

On Tue, Oct 22, 2002 at 08:54:35AM +0100, Shashi Verma wrote:

> Hello everyone,
> 
> -------------------------
> First of all, I would like to apologize if this is not
> the correct forum to address this question, since I am
> a relatively new user of gcc. If it is the case, I
> would request someone to kindly provide me the details
> of the appropriate forum
> -------------------------
> 
> I am working on Redhat 7.1, kernel 2.4.2-2, gcc
> version 2.96, libstdc++ version 2.96-81

This isn't the right place at all. Your question seems to be about using 
poll() under GNU/Linux using GCC 2.96 - nothing whatsoever to do with the
version 3 of the GNU C++ Standard Library - which is what this list is for.
GCC 2.96 is a RedHat-specific version of the compiler and is not supported
by the GCC team, support requests should be directed to RedHat (see the
output of "gcc --help" for details). Also, poll() is a C function, not part
of the C++ Standard Library. This question would probably be better suited
to a Linux programming forum, as it seems to be a problem with the Glibc
version of poll() under Linux.

> Now, I wasn't able to use the POLLRDNORM option when
> using the poll() function for I/O multiplexing. I had
> included <sys/poll.h>
> Upon enquiring in the man page, I found that
> POLLRDNORM is defined in <asm/poll.h>
> I included that too, but unfortunately, I got a
> redefinition for the pollfd struct.
> 
> A dirty way out is to take the definition for
> POLLRDNORM alone and put it in my code- but thats bad.
> 
> Any solutions- or is this an unfortunate bug?


Having said the above, I think that under Linux you need to define
_XOPEN_SOURCE and include <features.h> for the POLLRDNORM, POLLWRNORM etc
bitmasks. With this macro defined including <sys/poll.h> (or more portably,
<poll.h>) will declare the poll() function, the pollfd struct and all the
bitmasks.

e.g.

#define _XOPEN_SOURCE
#include <features.h>
#include <poll.h>

int main()
{
    struct pollfd s;
    s.fd = 0;
    s.events = POLLOUT|POLLWRNORM;
    return poll(&s, 1, 500);
}


If this isn't the right solution, don't blame me, as I said, this isn't
the right list for this question!  :)

HTH

Jon


-- 
"In times like these, it helps to recall that there have always been
 times like these."
	- Paul Harvey