Make WriteToClient take a const void * like any decent IO write function.

nx-X11/programs/Xserver/include/os.h

@@ -124,7 +124,7 @@ extern void FlushIfCriticalOutputPending(void);
 
 extern void SetCriticalOutputPending(void);
 
-extern int WriteToClient(ClientPtr /*who*/, int /*count*/, char* /*buf*/);
+extern int WriteToClient(ClientPtr /*who*/, int /*count*/, const void* /*__buf*/);
 
 extern void ResetOsBuffers(void);
 
@@ -444,7 +444,7 @@ typedef struct {
 extern CallbackListPtr ReplyCallback;
 typedef struct {
     ClientPtr client;
-    void * replyData;
+    const void * replyData;
     unsigned long dataLenBytes;
     unsigned long bytesRemaining;
     Bool startOfReply;

nx-X11/programs/Xserver/os/io.c

@@ -857,11 +857,12 @@ SetCriticalOutputPending(void)
  *****************/
 
 int
-WriteToClient (ClientPtr who, int count, char *buf)
+WriteToClient (ClientPtr who, int count, const void *__buf)
 {
     OsCommPtr oc;
     ConnectionOutputPtr oco;
     int padBytes;
+    const char *buf = __buf;
 #ifdef DEBUG_COMMUNICATION
     Bool multicount = FALSE;
 #endif
@@ -999,13 +1000,14 @@ WriteToClient (ClientPtr who, int count, char *buf)
  **********************/
 
 int
-FlushClient(ClientPtr who, OsCommPtr oc, char *extraBuf, int extraCount)
+FlushClient(ClientPtr who, OsCommPtr oc, const void *__extraBuf, int extraCount)
 {
     ConnectionOutputPtr oco = oc->output;
     int connection = oc->fd;
     XtransConnInfo trans_conn = oc->trans_conn;
     struct iovec iov[3];
     static char padBuffer[3];
+    const char *extraBuf = __extraBuf;
     long written;
     long padsize;
     long notWritten;
@@ -1051,7 +1053,7 @@ FlushClient(ClientPtr who, OsCommPtr oc, char *extraBuf, int extraCount)
 	}
 
 	InsertIOV ((char *)oco->buf, oco->count)
-	InsertIOV (extraBuf, extraCount)
+	InsertIOV ((char *)extraBuf, extraCount)
 	InsertIOV (padBuffer, padsize)
 
 	errno = 0;

nx-X11/programs/Xserver/os/osdep.h

@@ -187,7 +187,7 @@ typedef struct _osComm {
 extern int FlushClient(
     ClientPtr /*who*/,
     OsCommPtr /*oc*/,
-    char* /*extraBuf*/,
+    const void * /*__extraBuf*/,
     int /*extraCount*/
 );