How to create certificate request with OpenSSL library

Question

I am trying to create certificate request programmatically in iOS using openSSL. I got testKey.pem(private key) and test.csr finally and the first works well in linux(by openssl command), however test.csr seams strange and cannot be recognized and used properly. here is my code in OC.

- (void)genCertReq {
    if (!X509_REQ_set_version(csr.req, csr.ver)) {
        LOG(@"set_version failed");
        goto error;
    }
    [self fillDN]; 
    /* subject name */
    if (!X509_REQ_set_subject_name(csr.req, csr.subject)) {
        LOG(@"subject_name failed");
        goto error;
    }
    rsaPair = RSA_generate_key(bits, e, NULL, NULL);
    const char *keyPathChar = [SPFileManager openFile:testKey];
    BIO *bp = NULL;
    bp = BIO_new_file(keyPathChar, "w");
    PEM_write_bio_RSAPrivateKey(bp, rsaPair, NULL, NULL, 0, NULL, NULL);
    BIO_free(bp);
    /* pub key */
    if (1 != EVP_PKEY_assign_RSA(evpKey, rsaPair)) {
        LOG(@"assign_RSA failed");
        goto error;
    }
    if (!X509_REQ_set_pubkey(csr.req, evpKey)) {
        LOG(@"set_pubkey failed");
        goto error;
    }
    /* attribute */
    csr.md = EVP_sha1();
    if (!X509_REQ_digest(csr.req, csr.md, (unsigned char *)csr.mdout, (unsigned int *)&csr.mdlen)) {
        LOG(@"req_digest failed");
        goto error;
    }
    if (!X509_REQ_sign(csr.req, evpKey, csr.md)) {
        LOG(@"req_sign failed");
        goto error;
    }
    const char *csrPathChar = [SPFileManager openFile:csrName];
    bp = BIO_new_file(csrPathChar, "w");
    PEM_write_bio_X509_REQ(bp, csr.req);
    BIO_free(bp);

    OpenSSL_add_all_algorithms();
    if (X509_REQ_verify(csr.req, evpKey) < 0) {
        LOG(@"req_verify failed");
        goto error;
    }
    X509_REQ_free(csr.req);
    return;
error:
    X509_REQ_free(csr.req);
    return;
}

testKey.pem is in PKCS1 format and looks like --BEGIN RSA PRIVATE KEY---, and test.csr looks like ---BEGIN CERTIFICATE REQUEST--- which however I don't think is right.

Any help will be appreciated, thanks.