diff --git a/src/openssl.c b/src/openssl.c
index 225111fb..c708cbaf 100644
--- a/src/openssl.c
+++ b/src/openssl.c
@@ -48,7 +48,7 @@
 #define EVP_MAX_BLOCK_LENGTH 32
 #endif
 
-int
+static int
 read_openssh_private_key_from_memory(void **key_ctx, LIBSSH2_SESSION *session,
                                      const char *key_type,
                                      const char *filedata,
@@ -4611,7 +4611,7 @@ _libssh2_sk_pub_openssh_keyfilememory(LIBSSH2_SESSION *session,
     return rc;
 }
 
-int
+static int
 read_openssh_private_key_from_memory(void **key_ctx, LIBSSH2_SESSION *session,
                                      const char *key_type,
                                      const char *filedata,
diff --git a/src/openssl.h b/src/openssl.h
index de44e421..afa330f7 100644
--- a/src/openssl.h
+++ b/src/openssl.h
@@ -223,10 +223,10 @@ int _libssh2_sha1_init(libssh2_sha1_ctx *ctx);
                                          EVP_DigestFinal(ctx, out, NULL); \
                                          EVP_MD_CTX_free(ctx); \
                                      } while(0)
-#else
+#else /* !HAVE_OPAQUE_STRUCTS */
 #define libssh2_sha1_update(ctx, data, len) EVP_DigestUpdate(&(ctx), data, len)
 #define libssh2_sha1_final(ctx, out) EVP_DigestFinal(&(ctx), out, NULL)
-#endif
+#endif /* HAVE_OPAQUE_STRUCTS */
 int _libssh2_sha1(const unsigned char *message, size_t len,
                   unsigned char *out);
 #define libssh2_sha1(x,y,z) _libssh2_sha1(x,y,z)
@@ -246,11 +246,11 @@ int _libssh2_sha256_init(libssh2_sha256_ctx *ctx);
                                            EVP_DigestFinal(ctx, out, NULL); \
                                            EVP_MD_CTX_free(ctx); \
                                        } while(0)
-#else
+#else /* !HAVE_OPAQUE_STRUCTS */
 #define libssh2_sha256_update(ctx, data, len) \
     EVP_DigestUpdate(&(ctx), data, len)
 #define libssh2_sha256_final(ctx, out) EVP_DigestFinal(&(ctx), out, NULL)
-#endif
+#endif /* HAVE_OPAQUE_STRUCTS */
 int _libssh2_sha256(const unsigned char *message, size_t len,
                     unsigned char *out);
 #define libssh2_sha256(x,y,z) _libssh2_sha256(x,y,z)
@@ -270,11 +270,11 @@ int _libssh2_sha384_init(libssh2_sha384_ctx *ctx);
                                             EVP_DigestFinal(ctx, out, NULL); \
                                             EVP_MD_CTX_free(ctx); \
                                        } while(0)
-#else
+#else /* !HAVE_OPAQUE_STRUCTS */
 #define libssh2_sha384_update(ctx, data, len) \
     EVP_DigestUpdate(&(ctx), data, len)
 #define libssh2_sha384_final(ctx, out) EVP_DigestFinal(&(ctx), out, NULL)
-#endif
+#endif /* HAVE_OPAQUE_STRUCTS */
 int _libssh2_sha384(const unsigned char *message, size_t len,
                     unsigned char *out);
 #define libssh2_sha384(x,y,z) _libssh2_sha384(x,y,z)
@@ -294,11 +294,11 @@ int _libssh2_sha512_init(libssh2_sha512_ctx *ctx);
                                             EVP_DigestFinal(ctx, out, NULL); \
                                             EVP_MD_CTX_free(ctx); \
                                        } while(0)
-#else
+#else /* !HAVE_OPAQUE_STRUCTS */
 #define libssh2_sha512_update(ctx, data, len) \
     EVP_DigestUpdate(&(ctx), data, len)
 #define libssh2_sha512_final(ctx, out) EVP_DigestFinal(&(ctx), out, NULL)
-#endif
+#endif /* HAVE_OPAQUE_STRUCTS */
 int _libssh2_sha512(const unsigned char *message, size_t len,
                     unsigned char *out);
 #define libssh2_sha512(x,y,z) _libssh2_sha512(x,y,z)
@@ -319,11 +319,11 @@ int _libssh2_md5_init(libssh2_md5_ctx *ctx);
                                         EVP_DigestFinal(ctx, out, NULL); \
                                         EVP_MD_CTX_free(ctx); \
                                     } while(0)
-#else
+#else /* !HAVE_OPAQUE_STRUCTS */
 #define libssh2_md5_update(ctx, data, len) EVP_DigestUpdate(&(ctx), data, len)
 #define libssh2_md5_final(ctx, out) EVP_DigestFinal(&(ctx), out, NULL)
-#endif
-#endif
+#endif /* HAVE_OPAQUE_STRUCTS */
+#endif /* LIBSSH2_MD5 || LIBSSH2_MD5_PEM */
 
 #ifdef HAVE_OPAQUE_STRUCTS
 #define libssh2_hmac_ctx HMAC_CTX *
@@ -343,13 +343,13 @@ int _libssh2_md5_init(libssh2_md5_ctx *ctx);
 /* FIXME: upstream bug as of v5.6.0: datalen is int instead of size_t */
 #define libssh2_hmac_update(ctx, data, datalen) \
     HMAC_Update(ctx, data, (int)datalen)
-#else
+#else /* !LIBSSH2_WOLFSSL */
 #define libssh2_hmac_update(ctx, data, datalen) \
     HMAC_Update(ctx, data, datalen)
 #endif /* LIBSSH2_WOLFSSL */
 #define libssh2_hmac_final(ctx, data) HMAC_Final(ctx, data, NULL)
 #define libssh2_hmac_cleanup(ctx) HMAC_CTX_free(*(ctx))
-#else
+#else /* !HAVE_OPAQUE_STRUCTS */
 #define libssh2_hmac_ctx HMAC_CTX
 #define libssh2_hmac_ctx_init(ctx) \
     HMAC_CTX_init(&ctx)
@@ -368,7 +368,7 @@ int _libssh2_md5_init(libssh2_md5_ctx *ctx);
     HMAC_Update(&(ctx), data, datalen)
 #define libssh2_hmac_final(ctx, data) HMAC_Final(&(ctx), data, NULL)
 #define libssh2_hmac_cleanup(ctx) HMAC_cleanup(ctx)
-#endif
+#endif /* HAVE_OPAQUE_STRUCTS */
 
 extern void _libssh2_openssl_crypto_init(void);
 extern void _libssh2_openssl_crypto_exit(void);
@@ -417,15 +417,14 @@ typedef enum {
     LIBSSH2_EC_CURVE_NISTP521 = NID_secp521r1
 }
 libssh2_curve_type;
-#else
+#else /* !LIBSSH2_ECDSA */
 #define _libssh2_ec_key void
 #endif /* LIBSSH2_ECDSA */
 
 #if LIBSSH2_ED25519
 #define libssh2_ed25519_ctx EVP_PKEY
-
 #define _libssh2_ed25519_free(ctx) EVP_PKEY_free(ctx)
-#endif /* ED25519 */
+#endif /* LIBSSH2_ED25519 */
 
 #define _libssh2_cipher_type(name) const EVP_CIPHER *(*name)(void)
 #ifdef HAVE_OPAQUE_STRUCTS