How to compare two openssl X509 certificate object C++

Question

I have two X509 objects

X509 *cert1;
X509 *cert2;

How to I determine whether this two certificates are same or different? which property are identical for two same certificates?

Answer 1

X509_cmp(const X509 *a, const X509 *b) is perfect for byte by byte comparison of SHA_1 hash of two certificates. So @AlexBezuglyi is 100% correct. But actually I intended (but couldn't express in this question) to verify the server certificate whether its signed by the root certificate (trusted CA signed certificate).

Using X509_verify

The signature of int X509_verify is

int X509_verify(X509 * x509, EVP_PKEY * pkey);

Suppose of you have root certificate in root and server certificate in cert

X509 * root;
X509 * cert;

//Get local certificate into root
//Get server certificate into cert

//Get the public key.
EVP_PKEY * pubkey = X509_get_pubkey(root);

//verify. result less than or 0 means not verified or some error.
int result = X509_verify(cert, pubkey);

//free the public key.
EVP_PKEY_free(pubkey);