QTNCopy(QTNode *in)
{
	QTNode	   *out;

	/* since this function recurses, it could be driven to stack overflow. */
	check_stack_depth();

	out = (QTNode *) palloc(sizeof(QTNode));

	*out = *in;
	out->valnode = (QueryItem *) palloc(sizeof(QueryItem));
	*(out->valnode) = *(in->valnode);
	out->flags |= QTN_NEEDFREE;

	if (in->valnode->type == QI_VAL)
	{
		out->word = palloc(in->valnode->qoperand.length + 1);
		memcpy(out->word, in->word, in->valnode->qoperand.length);
		out->word[in->valnode->qoperand.length] = '\0';
		out->flags |= QTN_WORDFREE;
	}
	else
	{
		int			i;

		out->child = (QTNode **) palloc(sizeof(QTNode *) * in->nchild);

		for (i = 0; i < in->nchild; i++)
			out->child[i] = QTNCopy(in->child[i]);
	}

	return out;
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.