[Spread-users] [BUG][PATCH] fd to session troubles
tim at zope.com
Mon Feb 4 14:36:27 EST 2002
>> ... More or less. In fact, it doesn't compile out of the box,
>> because of EWOULDBLOCK that doesn't exist as such on Windows.
> Ok. I think this one might also not exist on some more esoteric Unixes.
EWOULDBLOCK is POSIX, and the same thing is called EAGAIN on some older
Unices. I've heard that there are systems where EWOULDBLOCK and EAGAIN both
exist but aren't equal, but don't know of a specific one. I'd risk defining
EWOULDBLOCK to EAGAIN if the latter exists but the former doesn't, do an
#error if both exist but aren't equal, and use EWOULDBLOCK exclusively.
> I know using the WSA error stuff is "better" on windows,
Worse than that: it's required, or you can have no idea what a -1 return
from a socket op on Windows means (the value of errno then isn't related to
the socket op at all).
> but isn't there at least a backwands compatible Posix errno error
> reporting that I can enable as default until everything is converted?
> It seems odd that windows has most of the posix/unix stuff (at least
> as a compatibility layer) but doesn't do error reporting the same way.
Windows was built for thread safety from the ground up, and errno isn't
threadsafe (at least not under compilers that haven't tricked errno into
being a thread-local storage gimmick -- a global vrbl shared across threads
just can't work). That's why all the Windows APIs use an error-reporting
function instead (they're threadsafe); about the only places they use errno
is where ANSI C requires it.
One pleasant approach is to use, e.g., "s_errno" for checking errno values
after socket ops, and then
#define s_errno WSAGetLastError()
on Windows and
#define s_errno errno
elsewhere. A platform-neutral set of constants to check against also needs
to be #define'd.
MS *used* to do the last part for you in winsock.h, but gave up because
conflicts with errno.h couldn't be resolved. There's still a commented-out
block of code for this in winsock.h:
* Windows Sockets errors redefined as regular Berkeley error constants.
* These are commented out in Windows NT to avoid conflicts with errno.h.
* Use the WSA constants instead.
#define EWOULDBLOCK WSAEWOULDBLOCK
#define EINPROGRESS WSAEINPROGRESS
#define EALREADY WSAEALREADY
#define ENOTSOCK WSAENOTSOCK
#define EDESTADDRREQ WSAEDESTADDRREQ
#define EMSGSIZE WSAEMSGSIZE
#define EPROTOTYPE WSAEPROTOTYPE
#define ENOPROTOOPT WSAENOPROTOOPT
#define EPROTONOSUPPORT WSAEPROTONOSUPPORT
#define ESOCKTNOSUPPORT WSAESOCKTNOSUPPORT
#define EOPNOTSUPP WSAEOPNOTSUPP
#define EPFNOSUPPORT WSAEPFNOSUPPORT
#define EAFNOSUPPORT WSAEAFNOSUPPORT
#define EADDRINUSE WSAEADDRINUSE
#define EADDRNOTAVAIL WSAEADDRNOTAVAIL
#define ENETDOWN WSAENETDOWN
#define ENETUNREACH WSAENETUNREACH
#define ENETRESET WSAENETRESET
#define ECONNABORTED WSAECONNABORTED
#define ECONNRESET WSAECONNRESET
#define ENOBUFS WSAENOBUFS
#define EISCONN WSAEISCONN
#define ENOTCONN WSAENOTCONN
#define ESHUTDOWN WSAESHUTDOWN
#define ETOOMANYREFS WSAETOOMANYREFS
#define ETIMEDOUT WSAETIMEDOUT
#define ECONNREFUSED WSAECONNREFUSED
#define ELOOP WSAELOOP
#define ENAMETOOLONG WSAENAMETOOLONG
#define EHOSTDOWN WSAEHOSTDOWN
#define EHOSTUNREACH WSAEHOSTUNREACH
#define ENOTEMPTY WSAENOTEMPTY
#define EPROCLIM WSAEPROCLIM
#define EUSERS WSAEUSERS
#define EDQUOT WSAEDQUOT
#define ESTALE WSAESTALE
#define EREMOTE WSAEREMOTE
> About the sp.c problem, I would think there has to be a way to
> set the returned error on Windows, libraries often have to change set
> what error applications who see them will get. Maybe a WSASetError() ? :-)
A (say) s_set_errno macro can use this to "do the right thing" so that the
s_errno macro suggested above works across boxes.
Be thankful you haven't bumped into BeOS or RISCOS yet <wink>.
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