preserve errno around the SIGIO handler

hw/xfree86/os-support/shared/sigio.c

@@ -101,6 +101,7 @@ xf86SIGIO (int sig)
     int	    i;
     fd_set  ready;
     struct timeval  to;
+    int save_errno = errno;	/* do not clobber the global errno */
     int	    r;
 
     ready = xf86SigIOMask;
@@ -117,6 +118,8 @@ xf86SIGIO (int sig)
     if (r > 0) {
       xf86Msg(X_ERROR, "SIGIO %d descriptors not handled\n", r);
     }
+    /* restore global errno */
+    errno = save_errno;
 }
 
 static int