diff -Nurd hdf-4.2.15.orig/hdf/src/hdfi.h hdf-4.2.15/hdf/src/hdfi.h
--- hdf-4.2.15.orig/hdf/src/hdfi.h	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/hdf/src/hdfi.h	2022-03-18 03:19:07.000000000 -0400
@@ -512,12 +512,13 @@
 #include <sys/types.h>
 #include <sys/file.h>               /* for unbuffered i/o stuff */
 #include <sys/stat.h>
-#ifdef __i386
+#if defined(__i386) || defined(__x86_64__)
 #ifndef INTEL86
 #define INTEL86   /* we need this Intel define or bad things happen later */
 #endif /* INTEL86 */
 #endif /* __i386 */
 
+#if defined(__i386) && !defined(__x86_64__)
 typedef void            VOID;
 typedef void            *VOIDP;
 typedef char            *_fcd;
@@ -906,6 +907,25 @@
 typedef double          float64;
 typedef int             intf;     /* size of INTEGERs in Fortran compiler */
 typedef int               hdf_pint_t;   /* an integer the same size as a pointer */
+#elif defined(__x86_64__)
+typedef void              VOID;
+typedef void              *VOIDP;
+typedef char              *_fcd;
+typedef char              char8;
+typedef unsigned char     uchar8;
+typedef char              int8;
+typedef unsigned char     uint8;
+typedef short int         int16;
+typedef unsigned short int uint16;
+typedef int               int32;
+typedef unsigned int      uint32;
+typedef int               intn;
+typedef unsigned int      uintn;
+typedef int               intf;     /* size of INTEGERs in Fortran compiler */
+typedef float             float32;
+typedef double            float64;
+typedef long              hdf_pint_t;   /* an integer the same size as a pointer */
+#endif
 #define _fcdtocp(desc) (desc)
 #define FNAME_POST_UNDERSCORE
 #define FILELIB UNIXBUFIO
diff -Nurd hdf-4.2.15.orig/hdf/test/mgr.c hdf-4.2.15/hdf/test/mgr.c
--- hdf-4.2.15.orig/hdf/test/mgr.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/hdf/test/mgr.c	2022-03-19 03:55:16.000000000 -0400
@@ -168,6 +168,7 @@
 extern void test_mgr_attr();
 extern void test_mgr_compress();
 extern void test_mgr_dup_images();
+extern void test_mgr_szip();
 
 /* Test outline:
     I. Interface Initialization
diff -Nurd hdf-4.2.15.orig/mfhdf/hdiff/hdiff_main.c hdf-4.2.15/mfhdf/hdiff/hdiff_main.c
--- hdf-4.2.15.orig/mfhdf/hdiff/hdiff_main.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/hdiff/hdiff_main.c	2022-03-18 03:21:36.000000000 -0400
@@ -12,6 +12,7 @@
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 
+#include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff -Nurd hdf-4.2.15.orig/mfhdf/libsrc/file.c hdf-4.2.15/mfhdf/libsrc/file.c
--- hdf-4.2.15.orig/mfhdf/libsrc/file.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/libsrc/file.c	2022-03-18 12:09:20.000000000 -0400
@@ -20,6 +20,7 @@
 #include <assert.h>
 #endif /* DEBUG */
 
+#include    <unistd.h>
 #include    <string.h>
 #include    <errno.h>
 #include    "local_nc.h"
diff -Nurd hdf-4.2.15.orig/mfhdf/ncdump/ncdump.c hdf-4.2.15/mfhdf/ncdump/ncdump.c
--- hdf-4.2.15.orig/mfhdf/ncdump/ncdump.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/ncdump/ncdump.c	2022-03-18 03:23:32.000000000 -0400
@@ -4,6 +4,7 @@
  *   $Id$
  *********************************************************************/
 
+#include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
diff -Nurd hdf-4.2.15.orig/mfhdf/ncgen/close.c hdf-4.2.15/mfhdf/ncgen/close.c
--- hdf-4.2.15.orig/mfhdf/ncgen/close.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/ncgen/close.c	2022-03-18 03:32:15.000000000 -0400
@@ -6,9 +6,7 @@
 
 #include <stdio.h>
 #include "ncgen.h"
-#ifdef EIP
 #include "genlib.h"
-#endif
 
 extern void fline(), cline();
 extern int netcdf_flag;
diff -Nurd hdf-4.2.15.orig/mfhdf/ncgen/main.c hdf-4.2.15/mfhdf/ncgen/main.c
--- hdf-4.2.15.orig/mfhdf/ncgen/main.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/ncgen/main.c	2022-03-18 03:23:53.000000000 -0400
@@ -4,6 +4,7 @@
  *   $Id$
  *********************************************************************/
 
+#include <unistd.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
diff -Nurd hdf-4.2.15.orig/mfhdf/ncgen/ncgentab.c hdf-4.2.15/mfhdf/ncgen/ncgentab.c
--- hdf-4.2.15.orig/mfhdf/ncgen/ncgentab.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/ncgen/ncgentab.c	2022-03-19 05:04:03.000000000 -0400
@@ -109,8 +109,8 @@
 #define DATA 276
 
 
-
-
+int yylex(void);
+void yyerror(char* s);
 /* Copy the first part of user declarations.  */
 #line 9 "../../../hdf4/mfhdf/ncgen/ncgen.y"
 
@@ -139,7 +139,7 @@
 void define_netcdf();		/* generates all define mode stuff */
 void load_netcdf();		/* generates variable puts */
 void close_netcdf();		/* generates close */
-
+const char *nctype(nc_type);
 void derror();			/* varargs message emitter */
 void *emalloc(), *erealloc();	/* malloc that checks for memory exhausted */
 void clearout();		/* initializes symbol table */
@@ -2350,7 +2350,7 @@
 
 void derror();
 
-yyerror(s)	/* called for yacc syntax error */
+void yyerror(s)	/* called for yacc syntax error */
      char *s;
 {
 	derror(s);
diff -Nurd hdf-4.2.15.orig/mfhdf/test/hdftest.c hdf-4.2.15/mfhdf/test/hdftest.c
--- hdf-4.2.15.orig/mfhdf/test/hdftest.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/test/hdftest.c	2022-03-19 04:04:43.000000000 -0400
@@ -65,6 +65,7 @@
 extern int test_datainfo();
 extern int test_external();
 extern int test_att_ann_datainfo();
+extern int test_dimensions();
 
 int 
 main(int argc, char *argv[])
diff -Nurd hdf-4.2.15.orig/mfhdf/test/tdatainfo.c hdf-4.2.15/mfhdf/test/tdatainfo.c
--- hdf-4.2.15.orig/mfhdf/test/tdatainfo.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/test/tdatainfo.c	2022-03-18 03:39:35.000000000 -0400
@@ -23,6 +23,9 @@
  * -BMR, Jul 2010
  ****************************************************************************/
 
+#ifndef DATAINFO_TESTER
+#define DATAINFO_TESTER /* to include mfdatainfo.h */
+#endif
 #include "mfhdf.h"
 
 #ifdef H4_HAVE_SYS_TYPES_H
@@ -44,9 +47,6 @@
 #define ssize_t int32
 #endif
 
-#ifndef DATAINFO_TESTER
-#define DATAINFO_TESTER /* to include mfdatainfo.h */
-#endif
 
 #ifdef H4_HAVE_LIBSZ
 #include "szlib.h"
diff -Nurd hdf-4.2.15.orig/mfhdf/test/tfile.c hdf-4.2.15/mfhdf/test/tfile.c
--- hdf-4.2.15.orig/mfhdf/test/tfile.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/test/tfile.c	2022-03-19 04:14:17.000000000 -0400
@@ -18,6 +18,8 @@
 #ifdef HDF
 
 #include "hdftest.h"
+#include "local_nc.h"
+intn make_datafilename(char* basename, char* testfile, unsigned int size);
 
 /********************************************************************
    Name: test_file_inuse() - tests preventing of an in-use file being
diff -Nurd hdf-4.2.15.orig/mfhdf/test/tncvargetfill.c hdf-4.2.15/mfhdf/test/tncvargetfill.c
--- hdf-4.2.15.orig/mfhdf/test/tncvargetfill.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/test/tncvargetfill.c	2022-03-19 04:02:11.000000000 -0400
@@ -36,6 +36,8 @@
 #define DIM0 20	/* this value is used to declare larger buffer for when
 		   reading past the maximum number of records in the file */
 
+int verify_info_data(int32 sds_id, int32 expected_dimsize, int16 *result);
+
 /********************************************************************
    Name: test_1dim_multivars() - tests reading/writing on multiple variables,
 	each has 1 dimension
diff -Nurd hdf-4.2.15.orig/mfhdf/test/tsd.c hdf-4.2.15/mfhdf/test/tsd.c
--- hdf-4.2.15.orig/mfhdf/test/tsd.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/test/tsd.c	2022-03-18 12:08:50.000000000 -0400
@@ -19,6 +19,7 @@
 
 #ifdef HDF
 
+#include <unistd.h>
 #include "hdftest.h"
 #include "hfile.h"
 
diff -Nurd hdf-4.2.15.orig/mfhdf/test/tszip.c hdf-4.2.15/mfhdf/test/tszip.c
--- hdf-4.2.15.orig/mfhdf/test/tszip.c	2020-03-03 12:40:50.000000000 -0500
+++ hdf-4.2.15/mfhdf/test/tszip.c	2022-03-19 04:14:22.000000000 -0400
@@ -16,6 +16,7 @@
 #ifdef H4_HAVE_LIBSZ
 #include "szlib.h"
 #endif
+intn make_datafilename(char* basename, char* testfile, unsigned int size);
 
 #define FILE_NAME8	"SDS_8_sziped.hdf"
 #define FILE_NAME16	"SDS_16_sziped.hdf"