Writing beyond a pointer

A data processing apparatus comprising:

• processing circuitry configured to perform data processing operations;
• a memory configured to store data which is subject to the data processing operations, wherein as part of the data processing operations, the processing circuitry is configured to maintain a buffer in the memory;
• a register configured to hold a write pointer indicative of a current write location in the buffer;
• and
• a cache configured to cache copies of the data which are subject to the data processing operations by the processing circuitry, wherein the copies of the data are stored in cache lines, wherein the cache is configured to perform allocation into the cache from the memory and write-back from the cache to the memory in cache line units of data, and
• wherein the processing circuitry is configured, when the processing circuitry performs a data write to the buffer at a location determined by the write pointer, to update the write pointer in an update direction corresponding to a progression direction of data writes in the buffer, and further locations in the progression direction in the buffer between the location indicated by the write pointer and a boundary location are signalled to be written with a predetermined value.