Date: Fri, 18 Feb 2000 12:12:44 -0500 (EST) From: Marian Stagarescu <marian@bile.skycache.com> To: freebsd-alpha@freebsd.org Subject: FD_SET error on 64 bit architecture Message-ID: <Pine.NEB.4.05.10002181157100.28545-100000@bile.skycache.com>
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Hello,
I am running FreeBSD 4.0-20000101-CURRENT on a DS-10 Alpha/64 bit and I
am getting an error when trying to FD_SET descriptors with particular
values.
Here is an example:
int fd;
fd_set fdset;
FD_ZERO(&fds);
fd=35;
FD_SET(fd,&fdset);
check: if(FD_ISSET(fd,&fdset)) reports fd unset.
I was able to identify the cause of the problem (or at least what I
believe to be the cause);
the macros or FD_SET, FD_ISSET (appended below
from /usr/include/sys/types.h)
work with longs on 8 bytes on alpha-64bit architectures.
having this will result in a value of 64 for NFDBITS.
Trying to do FD_SET(fd,..) with fd=35 will force a shift
(1 << fd % NFDBITS)
which translates into
"shift a 32-bit (the 1 is an int on 32-bit) by 35 bits"
which is shifting 1 out and the result is 0, hence fd unset.
I choose to redefine the FD_SET, FD_ISSET macros to use a (long) 1 instead
of an 1 and this seems to work.
This looks to me as a portability problem to 64-bit arch. Is this correct
? Does anybody experienced this ? Are there any known problems with
64-bits arch ?
Thanks,
Marian Stagarescu
Cidera, Inc.
#define NBBY 8 /* number of bits in a byte */
/*
* Select uses bit masks of file descriptors in longs. These macros
* manipulate such bit fields (the filesystem macros use chars).
* FD_SETSIZE may be defined by the user, but the default here should
* be enough for most uses.
*/
#ifndef FD_SETSIZE
#define FD_SETSIZE 1024
#endif
typedef long fd_mask;
#define NFDBITS (sizeof(fd_mask) * NBBY) /* bits per mask */
#ifndef howmany
#define howmany(x, y) (((x) + ((y) - 1)) / (y))
#endif
typedef struct fd_set {
fd_mask fds_bits[howmany(FD_SETSIZE, NFDBITS)];
} fd_set;
#define FD_SET(n, p) ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) %
NFDBITS)))
#define FD_CLR(n, p) ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) %
NFDBITS)))
#define FD_ISSET(n, p) ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) %
NFDBITS)))
#define FD_COPY(f, t) bcopy(f, t, sizeof(*(f)))
#define FD_ZERO(p) bzero(p, sizeof(*(p)))
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