sk_pop
(type *)sk_pop(CHECKED_STACK_OF(type, st))
#define sk_OPENSSL_STRING_pop(st) (char *)sk_pop(CHECKED_STACK_OF(OPENSSL_STRING, st))
#define sk_OPENSSL_BLOCK_pop(st) (void *)sk_pop(CHECKED_STACK_OF(OPENSSL_BLOCK, st))
#define sk_OPENSSL_PSTRING_pop(st) (OPENSSL_STRING *)sk_pop(CHECKED_STACK_OF(OPENSSL_PSTRING, st))
void *sk_pop(_STACK *st);