pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE startsize, PCRE2_SIZE maxsize, pcre2_general_context *gcontext);
This function is used to create a stack for use by the code compiled by the JIT compiler. The first two arguments are a starting size for the stack, and a maximum size to which it is allowed to grow. The final argument is a general context, for memory allocation functions, or NULL for standard memory allocation. The result can be passed to the JIT run-time code by calling pcre2_jit_stack_assign() to associate the stack with a compiled pattern, which can then be processed by pcre2_match() or pcre2_jit_match(). A maximum stack size of 512KiB to 1MiB should be more than enough for any pattern. For more details, see the pcre2jit page.
There is a complete description of the PCRE2 native API in the pcre2api page and a description of the POSIX API in the pcre2posix page.