Clearing a Blocks Buffers

[Luke Berndt]

Is there a good method for clearing or resetting a block’s buffers? 

I have a program that tunes to different frequencies and is also started & paused. I want to clear out any of the existing samples in the buffers between blocks to make sure I am getting the current signal in and not something that was left over. 

I have tried the following approach but it sometimes leads to segfaults with some blocks.  Can this be done? Is there a better way to do this or achieve the same results?

gr::block_detail_sptr detail;

gr::block_sptr grblock = cast_to_block_sptr(block);

detail = grblock->detail();

detail->reset_nitem_counters();