n X509V3_get_d2i() and its variants will return NULL if the extension is not found, occurs multiple times or cannot be decoded. It is possible to determine the precise reason by checking the value of <i>*crit</i>.</p>

<p>The function X509V3_add1_i2d() and its variants allocate <b>X509_EXTENSION</b> objects on STACK <i>*x</i> depending on <i>flags</i>. The <b>X509_EXTENSION</b> objects must be explicitly freed using X509_EXTENSION_free().</p>

<h1 id="SUPPORTED-EXTENSIONS">SUPPORTED EXTENSIONS</h1>

<p>The 