Thank you @rizlik for the heads-up on this change as related to #6201 from @PaulMartinsen.

I've been able to reproduce the problem and confirmed that your fix works properly on the Espressif ESP-IDF for the ESP32.

I've confirmed that void* realloc(void* ptr, size_t size) is implemented in the Espressif components/newlib/heap.c for ESP-IDF v5. It is also implemented in the same place for EDP-IDF v4.

I've tested this with SINGLE_THREADED both defined or not. I then tested with OPENSSL_EXTRA enabled or not. In all cases the Espressif wolfssl tests on my ED25519_SHA2_fix branch all succeeded.

Note that some combinations on the current wolfSSL release will not work, such as the ED25519 problems noted in #5948 that are fixed in my branch. PR coming as soon as I can clean everything up & complete more testing.

This now passes all the tests