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. If the stack couldn't be allocated or the values passed were not reasonable, NULL will be returned. 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.