comment #1:

> A bit more details would be nice. What's the documentation discrepancy and where did you read the docs?

There is either a bug in netconn_recv_tcp_pbuf or a clarification in the documentation is needed.

I am using the ESP32 IDE latest commit 625bd5e
https://github.com/espressif/esp-idf/
lwIP CHANGELOG says STABLE-2.1.2

My code:

pb=NULL;
if(ERR_OK != netconn_recv_tcp_pbuf(nconn, &pb))
{
   assert(pb == NULL); /* fails */
   if(pb)
      pbuf_free(pb); /* Crashes in pbuf_free() if above assert is removed */
}