https://github.com/jessek/hashdeep/commit/6ef69a26126ee4e69a25392fd456b8a66c51dffd
--- src/hash.cpp.orig	2015-04-01 02:12:52.000000000 +0200
+++ src/hash.cpp	2017-10-07 16:05:39.000000000 +0200
@@ -279,7 +279,7 @@
 		MAP_FILE|
 #endif
 		MAP_SHARED,fd,0);
-	    if(fdht->base>0){		
+	    if(fdht->base != (void *) -1){
 		/* mmap is successful, so set the bounds.
 		 * if it is not successful, we default to reading the fd
 		 */