_free() decrements the reference count of <b>X509</b> structure <b>a</b> and frees it up if the reference count is zero. If <b>a</b> is NULL nothing is done.</p>

<p>X509_up_ref() increments the reference count of <b>a</b>.</p>

<p>X509_chain_up_ref() increases the reference count of all certificates in chain <b>x</b> and returns a copy of the stack, or an empty stack if <b>a</b> is NULL.</p>

<p>OSSL_STACK_OF_X509_free() deallocates the given list of pointers to certificates after calling X509_free() on al