[zeromq-dev] patch: non-blocking tcp accept
georgen at neillnet.com
Tue Apr 28 13:11:27 CEST 2009
On Tue, Apr 28, 2009 at 5:53 AM, Martin Sustrik <sustrik at fastmq.com> wrote:
>>> The one thing I'm unsure of is EAGAIN/EWOULDBLOCK distinction. It seems
>>> that both Linux and Win32 assign the same numeric value to both errors.
>>> I am not sure of other platforms.
>>> POSIX says:
>>> Resource unavailable, try again (may be the same value as
>>> Operation would block (may be the same value as [EAGAIN]).
>>> Pretty confusing...
>> from /usr/include/errno.h on AIX 5.3 ...
>> /* non-blocking and interrupt i/o */
>> * AIX returns EAGAIN where 4.3BSD used EWOULDBLOCK;
>> * but, the standards insist on unique errno values for each errno.
>> * A unique value is reserved for users that want to code case
>> * statements for systems that return either EAGAIN or EWOULDBLOCK.
>> #if _XOPEN_SOURCE_EXTENDED==1
>> #define EWOULDBLOCK EAGAIN /* Operation would block */
>> #else /* _XOPEN_SOURCE_EXTENDED */
>> #define EWOULDBLOCK 54
>> #endif /* _XOPEN_SOURCE_EXTENDED */
>> Might help de-confuse?
> Oh my. It's even worse then I've expected :) The actual values may change
> depending on macros defined.
> I've checked Solaris in the meantime - same value for both errors.
> Anyway, it seems that checking for both errors everywhere we are checking
> for one of the two at the moment would yield a sane result.
I believe that to be an acceptable solution (and common-place).
Quite possible to throw in some macro magic,
#if EAGAIN != EWOULDBLOCK
// deal with possible EWOULDBLOCK
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