socklen_t (Re: Multicast problems [PATCH])
deischen at freebsd.org
Wed Jun 20 12:34:50 UTC 2007
On Wed, 20 Jun 2007, Stefan Farfeleder wrote:
> On Tue, Jun 19, 2007 at 06:36:39PM -0400, Daniel Eischen wrote:
>> POSIX states that:
>> o The <sys/socket.h> header shall define the type socklen_t,
>> which is an integer type of width of at least 32 bits; see
>> APPLICATION USAGE.
>> and goes on to state:
>> o The <sys/socket.h> header shall define the unsigned integer
>> type sa_family_t.
>> This seems to imply that our socklen_t should not be an unsigned
>> integer (uint32_t), but a signed integer. In APPLICATION USAGE,
>> POSIX states:
> I don't understand how you come to that conclusion. Why does not
> mentioning whether socklen_t is signed or unsigned imply it should be
Because it explicitly says unsigned for sa_family_t and does not
say unsigned for socklen_t. To me, "integer" means a C (signed)
integer. The fact that older APIs and implementations used "int"
might support the argument to use int32_t just for compatibility
reasons. As it stands now, portable code has to have some sort
of autoconfig to determine whether or not to use socklen_t or int.
I don't see how you can do this with #ifdefs unless you know
OS version numbers and when socklen_t first got introduced.
>> To forestall portability problems, it is recommended that
>> applications not use values larger than 23^1 -1 for the
>> socklen_t type.
> That just means that those values will wrap to negative values if
> socklen_t is a signed integer type.
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