On 2019-04-24 14:50, Eric Blake wrote: > On 4/24/19 3:36 PM, Hans-Bernhard Bröker wrote: >> Am 24.04.2019 um 19:54 schrieb Eliot Moss: >>> On 4/24/2019 12:43 PM, Corinna Vinschen wrote: >> >>>> Since MSG_EOR isn't implemented in the underlying transport layer, >>>> there's no way to implement it in userspace. That's why it's not >>>> defined in Cygwin's headers. If you have an idea how to implement >>>> this in plain userspace, feel free to provide patches. >>> >>> I don't have a direct interest in this issue, but I do have a wondering. >>> If Cygwin fails to define an error code -- even if the error cannot >>> actually happen under Cygwin -- isn't that a problem when trying to >>> compile imported software? >> > > Well, MSG_EOR is not an error, but we can certainly do better than not > defining it at all. My suggestion for the least-cost implementation: > > - add a define for MSG_EOR to a non-zero value that is bitwise distinct > from other required MSG_ values > - return EOPNOTSUPP on attempts to use the flag in > send()/sendmsg()/sendto() (POSIX permits that failure for protocols that > don't support it - and none of Cygwin's protocols support it) > - optionally, document that MSG_EOR will never be set in the results > returned by recvmsg() (POSIX says it will only be set on protocols that > support it - and none of Cygwin's protocols support it) > > This will at least let software compile that attempts to use it, and > hopefully that software is robust to the fact that send() may reject the > flag and that recvmsg() cannot reliably report use of that flag. > >> >> Either way, as Standardese goes, this is sufficiently unclear that it >> IMHO calls for a defect report to the governing body of this standard. > > You're welcome to do so: > http://austingroupbugs.net/main_page.php > > although I personally thought POSIX was clear enough that MSG_EOR is > required to be defined, even if only so that it can trigger send() > errors showing that it is unsupported.
Would it be allowed and valid to #define MSG_EOR 0 to simplify lack of support? -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple