#include <pcre2.h>
PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *match_data);
This function returns a pointer to the vector of offsets that forms part of the given match data block. The number of pairs can be found by calling pcre2_get_ovector_count().
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.