Windows - fix getsockopt calls for narrower than int options

Windows unhelpfully writes to only one byte of the output buffer
when getsockopt is called for a boolean option. Therefore we have
to zero initialise the int rather than initialising to -1 as was
done before.
This in general only works for little endian architecture, because
the word would look like 0x01000000 on big endian. So I have added
some compile time asserts in the assumption that windows is always
little endian. This is ok for comparisons with 0/false, but not
comparisons with true or nonzero values.
In the case of IPV6_V6ONLY, it is documented as DWORD (unsigned int)
but on some windows versions it is returned as a boolean triggering
the warning. I removed the warning, as the conversion to int works on
both LE and BE since it is only compared with zero.

Task-number: QTBUG-23488
Change-Id: I3c586d1ada76465fc045a82661f289920c657a4c
Reviewed-by: Richard J. Moore <rich@kde.org>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>
Reviewed-by: Andreas Holzammer <andreas.holzammer@kdab.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/src/network/socket/qnativesocketengine_win.cpp b/src/network/socket/qnativesocketengine_win.cpp
index d7bbe7eb86..93a470c77f 100644
--- a/src/network/socket/qnativesocketengine_win.cpp
+++ b/src/network/socket/qnativesocketengine_win.cpp
@@ -427,10 +427,14 @@ int QNativeSocketEnginePrivate::option(QNativeSocketEngine::SocketOption opt) co
         break;
     }
 
-    int v = -1;
+#if Q_BYTE_ORDER != Q_LITTLE_ENDIAN
+#error code assumes windows is little endian
+#endif
+    int v = 0; //note: windows doesn't write to all bytes if the option type is smaller than int
     QT_SOCKOPTLEN_T len = sizeof(v);
-    if (getsockopt(socketDescriptor, level, n, (char *) &v, &len) != -1)
+    if (getsockopt(socketDescriptor, level, n, (char *) &v, &len) == 0)
         return v;
+    WS_ERROR_DEBUG(WSAGetLastError());
     return -1;
 }
 
@@ -563,12 +567,10 @@ bool QNativeSocketEnginePrivate::fetchConnectionParameters()
 #if defined (IPV6_V6ONLY)
     // determine if local address is dual mode
     DWORD ipv6only = 0;
-    int optlen = sizeof(ipv6only);
+    QT_SOCKOPTLEN_T optlen = sizeof(ipv6only);
     if (localAddress == QHostAddress::AnyIPv6
         && QSysInfo::windowsVersion() >= QSysInfo::WV_6_0
         && !getsockopt(socketDescriptor, IPPROTO_IPV6, IPV6_V6ONLY, (char*)&ipv6only, &optlen )) {
-            if (optlen != sizeof(ipv6only))
-                qWarning("unexpected size of IPV6_V6ONLY socket option");
             if (!ipv6only) {
                 socketProtocol = QAbstractSocket::AnyIPProtocol;
                 localAddress = QHostAddress::Any;