ERR_set_mark,
    ERR_pop_to_mark — set marks
    and pop OpenSSL errors until mark
#include
    <openssl/err.h>
int
  
  ERR_set_mark(void);
int
  
  ERR_pop_to_mark(void);
ERR_set_mark()
    sets a mark on the current topmost error record if there is one.
ERR_pop_to_mark()
    will pop the top of the error stack until a mark is found. The mark is then
    removed. If there is no mark, the whole stack is removed.
ERR_set_mark() returns 0 if the error
    stack is empty, otherwise 1.
ERR_pop_to_mark() returns 0 if there was
    no mark in the error stack, which implies that the stack became empty,
    otherwise 1.
ERR_set_mark() and
    ERR_pop_to_mark() first appeared in OpenSSL 0.9.8
    and have been available since OpenBSD 4.5.