How does one implement a circular buffer in Pd?
[tabwrite~] seems unequipped for the job, and [tabsend~] is for a specific purpose not directly related to circular buffers. [delwrite~] must be circular, but as it doesn't use an array, then you can't use the recorded signal freely (so e.g. a grain delay effect would have to do some really fancy tap dancing).
The only thing I can think of is to make the array a multiple of the block size, and [bang( it exactly at the right time, every cycle. I'm not certain that Pd's timing objects can do this with sample accuracy...? At 44.1 kHz, a 65536-sample buffer is 1486.07709751 milliseconds. I can imagine that (single precision!) rounding error would eventually cause glitches.