Close #12950: multiprocessing "test_fd_transfer" fails under OpenIndiana

Modules/_multiprocessing/multiprocessing.c

@@ -97,31 +97,37 @@ ProcessingCtrlHandler(DWORD dwCtrlType)
 /* Functions for transferring file descriptors between processes.
    Reimplements some of the functionality of the fdcred
    module at http://www.mca-ltd.com/resources/fdcred_1.tgz. */
+/* Based in http://resin.csoft.net/cgi-bin/man.cgi?section=3&topic=CMSG_DATA */
 
 static PyObject *
 multiprocessing_sendfd(PyObject *self, PyObject *args)
 {
     int conn, fd, res;
-    char dummy_char;
-    char buf[CMSG_SPACE(sizeof(int))];
-    struct msghdr msg = {0};
     struct iovec dummy_iov;
+    char dummy_char;
+    struct msghdr msg;
     struct cmsghdr *cmsg;
+    union {
+        struct cmsghdr hdr;
+        unsigned char buf[CMSG_SPACE(sizeof(int))];
+    } cmsgbuf;
 
     if (!PyArg_ParseTuple(args, "ii", &conn, &fd))
         return NULL;
 
     dummy_iov.iov_base = &dummy_char;
     dummy_iov.iov_len = 1;
-    msg.msg_control = buf;
-    msg.msg_controllen = sizeof(buf);
+
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_control = &cmsgbuf.buf;
+    msg.msg_controllen = sizeof(cmsgbuf.buf);
     msg.msg_iov = &dummy_iov;
     msg.msg_iovlen = 1;
+
     cmsg = CMSG_FIRSTHDR(&msg);
+    cmsg->cmsg_len = CMSG_LEN(sizeof(int));
     cmsg->cmsg_level = SOL_SOCKET;
     cmsg->cmsg_type = SCM_RIGHTS;
-    cmsg->cmsg_len = CMSG_LEN(sizeof(int));
-    msg.msg_controllen = cmsg->cmsg_len;
     * (int *) CMSG_DATA(cmsg) = fd;
 
     Py_BEGIN_ALLOW_THREADS
@@ -138,20 +144,26 @@ multiprocessing_recvfd(PyObject *self, PyObject *args)
 {
     int conn, fd, res;
     char dummy_char;
-    char buf[CMSG_SPACE(sizeof(int))];
-    struct msghdr msg = {0};
     struct iovec dummy_iov;
+    struct msghdr msg = {0};
     struct cmsghdr *cmsg;
+    union {
+        struct cmsghdr hdr;
+        unsigned char buf[CMSG_SPACE(sizeof(int))];
+    } cmsgbuf;
 
     if (!PyArg_ParseTuple(args, "i", &conn))
         return NULL;
 
     dummy_iov.iov_base = &dummy_char;
     dummy_iov.iov_len = 1;
-    msg.msg_control = buf;
-    msg.msg_controllen = sizeof(buf);
+
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_control = &cmsgbuf.buf;
+    msg.msg_controllen = sizeof(cmsgbuf.buf);
     msg.msg_iov = &dummy_iov;
     msg.msg_iovlen = 1;
+
     cmsg = CMSG_FIRSTHDR(&msg);
     cmsg->cmsg_level = SOL_SOCKET;
     cmsg->cmsg_type = SCM_RIGHTS;