fixed gcc7 format-truncation warning (#3069)

fixes #1800

src/libopensc/pkcs15-openpgp.c

@@ -628,6 +628,9 @@ sc_pkcs15emu_openpgp_init(sc_pkcs15_card_t *p15card)
 	LOG_FUNC_RETURN(ctx, r);
 }
 
+// see https://stackoverflow.com/a/10536254 for explanation
+#define LEN_MAX_INT_AS_STR (3 * sizeof(int) + 2)
+
 static int
 sc_pkcs15emu_openpgp_add_data(sc_pkcs15_card_t *p15card)
 {
@@ -639,8 +642,8 @@ sc_pkcs15emu_openpgp_add_data(sc_pkcs15_card_t *p15card)
 	for (i = 1; i <= PGP_NUM_PRIVDO; i++) {
 		sc_pkcs15_data_info_t dat_info;
 		sc_pkcs15_object_t dat_obj;
-		char name[8];
-		char path[9];
+		char name[6 + LEN_MAX_INT_AS_STR];
+		char path[7 + LEN_MAX_INT_AS_STR];
 		u8 content[254];
 		memset(&dat_info, 0, sizeof(dat_info));
 		memset(&dat_obj, 0, sizeof(dat_obj));