build: don't use const for ed25519/cosi if gcc<5

ed25519-donna/ed25519.c

@@ -45,7 +45,7 @@ ed25519_publickey(const ed25519_secret_key sk, ed25519_public_key pk) {
 }
 
 int
-ed25519_cosi_combine_publickeys(ed25519_public_key res, const ed25519_public_key *pks, size_t n) {
+ed25519_cosi_combine_publickeys(ed25519_public_key res, CONST ed25519_public_key *pks, size_t n) {
 	size_t i = 0;
 	ge25519 P;
 	ge25519_pniels sump;
@@ -76,7 +76,7 @@ ed25519_cosi_combine_publickeys(ed25519_public_key res, const ed25519_public_key
 }
 
 void
-ed25519_cosi_combine_signatures(ed25519_signature res, const ed25519_public_key R, const ed25519_cosi_signature *sigs, size_t n) {
+ed25519_cosi_combine_signatures(ed25519_signature res, const ed25519_public_key R, CONST ed25519_cosi_signature *sigs, size_t n) {
 	bignum256modm s, t;
 	size_t i = 0;
 

ed25519-donna/ed25519.h

@@ -5,24 +5,32 @@
 extern "C" {
 #endif
 
-typedef unsigned char ed25519_cosi_signature[32];
 typedef unsigned char ed25519_signature[64];
 typedef unsigned char ed25519_public_key[32];
 typedef unsigned char ed25519_secret_key[32];
 
 typedef unsigned char curve25519_key[32];
 
+typedef unsigned char ed25519_cosi_signature[32];
+
 void ed25519_publickey(const ed25519_secret_key sk, ed25519_public_key pk);
 
-int ed25519_cosi_combine_publickeys(ed25519_public_key res, const ed25519_public_key *pks, size_t n);
-void ed25519_cosi_combine_signatures(ed25519_signature res, const ed25519_public_key R, const ed25519_cosi_signature *sigs, size_t n);
-void ed25519_cosi_sign(const unsigned char *m, size_t mlen, const ed25519_secret_key key, const ed25519_secret_key nonce, const ed25519_public_key R, const ed25519_public_key pk, ed25519_cosi_signature sig);
 int ed25519_sign_open(const unsigned char *m, size_t mlen, const ed25519_public_key pk, const ed25519_signature RS);
 void ed25519_sign(const unsigned char *m, size_t mlen, const ed25519_secret_key sk, const ed25519_public_key pk, ed25519_signature RS);
 
 void curve25519_scalarmult(curve25519_key mypublic, const curve25519_key secret, const curve25519_key basepoint);
 void curve25519_scalarmult_basepoint(curve25519_key mypublic, const curve25519_key secret);
 
+#if __GNUC__ > 4
+#define CONST const
+#else
+#define CONST
+#endif
+
+int ed25519_cosi_combine_publickeys(ed25519_public_key res, CONST ed25519_public_key *pks, size_t n);
+void ed25519_cosi_combine_signatures(ed25519_signature res, const ed25519_public_key R, CONST ed25519_cosi_signature *sigs, size_t n);
+void ed25519_cosi_sign(const unsigned char *m, size_t mlen, const ed25519_secret_key key, const ed25519_secret_key nonce, const ed25519_public_key R, const ed25519_public_key pk, ed25519_cosi_signature sig);
+
 #if defined(__cplusplus)
 }
 #endif