No arithmatic on void pointer - found by Flexelint

src/vdfp_pipe.c

@@ -372,7 +372,7 @@ check_pid(struct vdp_state *state, struct vsl_log *vsl, int options)
 
 static int v_matchproto_(vdp_bytes_f)
 vdp_bytes(struct vdp_ctx *ctx, enum vdp_action act, void **priv,
-	  const void *ptr, ssize_t len)
+	  const void *ptra, ssize_t len)
 {
 	struct vdp_state *state;
 	struct pollfd *fds;
@@ -380,8 +380,10 @@ vdp_bytes(struct vdp_ctx *ctx, enum vdp_action act, void **priv,
 	ssize_t nbytes;
 	struct VPFX(pipe_vdp) *obj;
 	enum vdp_action act_bytes = VDP_FLUSH;
+	const char *ptr;
 
 	CHECK_OBJ_NOTNULL(ctx, VDP_CTX_MAGIC);
+	ptr = ptra;
 	assert(len >= 0);
 	AN(priv);
 	CAST_OBJ_NOTNULL(state, *priv, PIPE_VDP_STATE_MAGIC);