pcre2_jit_stack_assign man page
PCRE2 — Perl-compatible regular expressions (revised API)
void pcre2_jit_stack_assign(pcre2_match_context *mcontext, pcre2_jit_callback callback_function, void *callback_data);
This function provides control over the memory used by JIT as a run-time stack when pcre2_match() or pcre2_jit_match() is called with a pattern that has been successfully processed by the JIT compiler. The information that determines which stack is used is put into a match context that is subsequently passed to a matching function. The arguments of this function are:
mcontext a pointer to a match context
callback a callback function
callback_data a JIT stack or a value to be passed to the callback
If callback is NULL and callback_data is NULL, an internal 32K block on the machine stack is used.
If callback is NULL and callback_data is not NULL, callback_data must be a valid JIT stack, the result of calling pcre2_jit_stack_create().
If callback not NULL, it is called with callback_data as an argument at the start of matching, in order to set up a JIT stack. If the result is NULL, the internal 32K stack is used; otherwise the return value must be a valid JIT stack, the result of calling pcre2_jit_stack_create().
You may safely use the same JIT stack for multiple patterns, as long as they are all matched in the same thread. In a multithread application, each thread must use its own JIT stack. 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.