@@ -36,17 +36,10 @@
 #   else
 #	define CONST86
 #   endif
 #endif
 
-/*
- * Backwards compatibility for size type change
- */
-#if TCL_MAJOR_VERSION < 9 && TCL_MINOR_VERSION < 7
-    #define TCL_SIZE_MODIFIER ""
-#endif
-
 #include <openssl/ssl.h>
 #include <openssl/err.h>
 #include <openssl/rand.h>
 #include <openssl/opensslv.h>
 
@@ -171,11 +164,11 @@
 	BIO *p_bio;		/* Parent BIO (that is layered on Tcl_Channel) */
 
 	unsigned char *protos;	/* List of supported protocols in protocol format */
 	unsigned int protos_len; /* Length of protos */
 
-	char *err;
+	const char *err;
 } State;
 
 #ifdef USE_TCL_STUBS
 #ifndef Tcl_StackChannel
 #error "Unable to compile on this version of Tcl"
@@ -185,10 +178,29 @@
 #if TCL_MAJOR_VERSION < 9
     typedef char tls_free_type;
 #else
     typedef void tls_free_type;
 #endif
+
+#ifndef JOIN
+#  define JOIN(a,b) JOIN1(a,b)
+#  define JOIN1(a,b) a##b
+#endif
+
+#ifndef TCL_UNUSED
+# if defined(__cplusplus)
+#   define TCL_UNUSED(T) T
+# elif defined(__GNUC__) && (__GNUC__ > 2)
+#   define TCL_UNUSED(T) T JOIN(dummy, __LINE__) __attribute__((unused))
+# else
+#   define TCL_UNUSED(T) T JOIN(dummy, __LINE__)
+# endif
+#endif
+
+#if (TCL_MAJOR_VERSION < 9) && defined(TCL_MINOR_VERSION) && (TCL_MINOR_VERSION < 7) && !defined(TCL_SIZE_MODIFIER)
+#   define TCL_SIZE_MODIFIER ""
+#endif
 
 /*
  * Forward declarations
  */
 const Tcl_ChannelType *Tls_ChannelType(void);