extern const pcre2_code *regex_compile(const uschar *, mcs_flags, uschar **,
pcre2_compile_context *);
extern const pcre2_code *regex_must_compile(const uschar *, mcs_flags, BOOL);
extern const pcre2_code *regex_compile(const uschar *, mcs_flags, uschar **,
pcre2_compile_context *);
extern const pcre2_code *regex_must_compile(const uschar *, mcs_flags, BOOL);