--- ffs.h.orig	2021-03-07 06:41:24 UTC
+++ ffs.h
@@ -27,7 +27,15 @@
 #ifdef HAVE_ENDIAN_H
 #include <endian.h>
 #endif
+#include <stdint.h>
 
+#ifndef __WORDSIZE
+#if defined(UINTPTR_MAX) && defined(UINT64_MAX) && (UINTPTR_MAX == UINT64_MAX)
+#define __WORDSIZE 64
+#else
+#define __WORDSIZE 32
+#endif
+#endif
 
 #ifdef HAVE_FFS
 # define myffs(x) ffs(x)
@@ -54,12 +62,9 @@
 # define myffsl(x) myffsl_c(x)
 #endif
 
-#ifndef __BYTE_ORDER
+#ifndef BYTE_ORDER
 # error Need to define __BYTE_ORDER
 #endif
-#ifndef __WORDSIZE
-# error Need to define __WORDSIZE
-#endif
 
 //#ifndef HAVE_FFS
 #ifdef NEED_FFSL_C
@@ -93,7 +98,7 @@ static int myffsl_c(unsigned long val)
 }
 #endif
 
-#if __BYTE_ORDER == __BIG_ENDIAN || defined(TEST)
+#if BYTE_ORDER == BIG_ENDIAN || defined(TEST)
 /** Find last (highest) bit set in word val, returns a val b/w __WORDSIZE and 1, 0 if no bit is set */
 static int myflsl(unsigned long val)
 {
@@ -134,6 +139,8 @@ static int myflsl(unsigned long val)
 }
 int myffs_sse42(unsigned long);
 int myffsl_sse42(unsigned long);
+#else
+# define myflsl(x) flsl(x)
 #endif
 
 void probe_sse42();