Redefinition of symbols is not allowed with GCC < 4.3
and is a warning in clang
https://sourceforge.net/p/isync/bugs/35/
--- src/socket.c.orig	2017-10-01 03:42:35.000000000 -0500
+++ src/socket.c	2017-10-04 01:06:00.000000000 -0500
@@ -36,15 +36,6 @@
 #include <netinet/tcp.h>
 #include <arpa/inet.h>
 #include <netdb.h>
-#ifdef HAVE_LIBSSL
-# include <openssl/ssl.h>
-# include <openssl/err.h>
-# include <openssl/x509v3.h>
-# if OPENSSL_VERSION_NUMBER < 0x10100000L
-#  define X509_OBJECT_get0_X509(o) ((o)->data.x509)
-#  define X509_STORE_get0_objects(o) ((o)->objs)
-# endif
-#endif
 
 enum {
 	SCK_CONNECTING,
--- src/socket.h.orig	2017-10-01 03:42:35.000000000 -0500
+++ src/socket.h	2017-10-04 01:06:15.000000000 -0500
@@ -30,9 +30,13 @@
 #endif
 
 #ifdef HAVE_LIBSSL
-typedef struct ssl_st SSL;
-typedef struct ssl_ctx_st SSL_CTX;
-typedef struct stack_st _STACK;
+# include <openssl/ssl.h>
+# include <openssl/err.h>
+# include <openssl/x509v3.h>
+# if OPENSSL_VERSION_NUMBER < 0x10100000L
+#  define X509_OBJECT_get0_X509(o) ((o)->data.x509)
+#  define X509_STORE_get0_objects(o) ((o)->objs)
+# endif
 
 enum {
 	SSLv3 = 2,