where is size_t define?

[wziy520]

There are many function pass in size_t variables, but not get any typedef for size_t,

Where to find it? build my code about encrypt will pop warning

[ESP_igrr]

size_t is defined in <stddef.h>

you can find this file under xtensa-esp32-elf/lib/gcc/xtensa-esp32-elf/5.2.0/include/