diff --git a/hdf/src/hconv.h b/hdf/src/hconv.h
index d6a8748..7c4c17a 100644
--- a/hdf/src/hconv.h
+++ b/hdf/src/hconv.h
@@ -59,7 +59,7 @@
 /* CONSTANT DEFINITIONS                                                      */
 /*****************************************************************************/
 /* Generally Big-Endian machines */
-#if !defined(INTEL86) && !defined(MIPSEL) && !defined(DEC_ALPHA) && !defined(I860) && !defined(SUN386) && !(defined(__ia64) && !(defined(hpux) || defined(__hpux))) && !defined(__x86_64__) && !defined(__arm__) && !defined(__AARCH64EL__) && !defined(__LITTLE_ENDIAN__)
+#if !defined(INTEL86) && !defined(MIPSEL) && !defined(DEC_ALPHA) && !defined(I860) && !defined(SUN386) && !(defined(__ia64) && !(defined(hpux) || defined(__hpux))) && !defined(__x86_64__) && !defined(__arm__) && !defined(__AARCH64EL__) && !defined(__riscv) && !defined(__LITTLE_ENDIAN__)
 #       define UI8_IN     DFKnb1b   /* Unsigned Integer, 8 bits */
 #       define UI8_OUT    DFKnb1b
 #       define SI16_IN    DFKnb2b   /* S = Signed */
diff --git a/hdf/src/hdfi.h b/hdf/src/hdfi.h
index 42673a7..10b4933 100644
--- a/hdf/src/hdfi.h
+++ b/hdf/src/hdfi.h
@@ -81,6 +81,7 @@
 #define     DFMT_LINUX390       0x1111
 #define     DFMT_LINUXARM       0x4441
 #define     DFMT_LINUXAARCH64   0x4441
+#define     DFMT_LINUXRISCV64   0x4441
 
 /* I/O library constants */
 #define UNIXUNBUFIO 1
@@ -1384,6 +1385,57 @@ typedef long              hdf_pint_t;   /* an integer the same size as a pointer
 #endif
 #endif /* Linux AArch64 */
 
+/* Linux RISCV64 */
+#if defined(__riscv) && __riscv_xlen == 64
+
+#ifdef GOT_MACHINE
+If you get an error on this line more than one machine type has been defined.
+Please check your Makefile.
+#endif
+#define GOT_MACHINE
+
+#include <sys/file.h>               /* for unbuffered i/o stuff */
+#include <sys/stat.h>
+#define DF_MT             DFMT_LINUXRISCV64
+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 */
+#define FNAME_POST_UNDERSCORE
+#define _fcdtocp(desc) (desc)
+#ifdef  HAVE_FMPOOL
+#define FILELIB PAGEBUFIO  /* enable page buffering */
+#else
+#define FILELIB UNIXBUFIO
+#endif
+
+/* JPEG #define's - Look in the JPEG docs before changing - (Q) */
+
+/* Determine the memory manager we are going to use. Valid values are: */
+/*  MEM_DOS, MEM_ANSI, MEM_NAME, MEM_NOBS.  See the JPEG docs for details on */
+/*  what each does */
+#define JMEMSYS         MEM_ANSI
+
+#ifdef __GNUC__
+#define HAVE_STDC
+#define INCLUDES_ARE_ANSI
+#endif
+
+#endif /* Linux RISCV64 */
+
 #ifndef GOT_MACHINE
 No machine type has been defined.  Your Makefile needs to have someing like
 -DSUN or -DUNICOS in order for the HDF internal structures to be defined
diff --git a/mfhdf/fortran/jackets.c.in b/mfhdf/fortran/jackets.c.in
index b2ade09..a89355d 100644
--- a/mfhdf/fortran/jackets.c.in
+++ b/mfhdf/fortran/jackets.c.in
@@ -34,7 +34,7 @@
 
 struct ncfils {			/* This will be a common block from Fortran */
     double dd;
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
     int ll;
 #else
     long ll;
@@ -65,7 +65,7 @@ struct ncfils {			/* This will be a common block from Fortran */
 
 struct ncfils {			/* This will be a common block from Fortran */
     double dd;
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
     int ll;
 #else
     long ll;
@@ -420,7 +420,7 @@ stoig(shorts, ints, dims, basis, ndims)
 }
 #endif /* FORTRAN_HAS_NO_SHORT */
 
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 /*
  * Convert multi-dimensional array of NCLONGs stored in ints to packed
  * array of longs, in malloc'ed space.  Returns pointer to longs or NULL
@@ -908,7 +908,7 @@ nncvpt1(cdfid, varid, indices, value, rcode)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 	long          longs = *(int *)value;
@@ -1022,7 +1022,7 @@ nncvpt(cdfid, varid, start, count, value, rcode)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 	long *longs = itol (value, ncount, ndims);
@@ -1133,7 +1133,7 @@ nncvptg(cdfid, varid, start, count, stride, basis, value, rcode)
 	tmpbasis	= nctypelen(NC_LONG);
     else
 #endif
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
     if (datatype == NC_LONG)
 	tmpbasis	= sizeof(int);
     else
@@ -1190,7 +1190,7 @@ nncvptg(cdfid, varid, start, count, stride, basis, value, rcode)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 	long *longs = itolg (value, ncount, nbasis, ndims);
@@ -1326,7 +1326,7 @@ nncvgt1(cdfid, varid, indices, value, rcode)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 	long          longs;
@@ -1468,7 +1468,7 @@ nncvgt(cdfid, varid, start, count, value, rcode)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 	long iocount = dimprod (ncount, ndims);	/* product of dimensions */
@@ -1606,7 +1606,7 @@ nncvgtg(cdfid, varid, start, count, stride, basis, value, rcode)
 	tmpbasis	= nctypelen(NC_LONG);
     else
 #endif
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
     if (datatype == NC_LONG)
 	tmpbasis	= sizeof(int);
     else
@@ -1677,7 +1677,7 @@ nncvgtg(cdfid, varid, start, count, stride, basis, value, rcode)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 	long iocount = dimprod (ncount, ndims);	/* product of dimensions */
@@ -1843,7 +1843,7 @@ nncapt(cdfid, varid, attname, datatype, attlen, value, rcode, attnamelen)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) *datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 	long *longs = itol (value, attlen, 1);
@@ -2008,7 +2008,7 @@ nncagt(cdfid, varid, attname, value, rcode, attnamelen)
 	return;
     }				/* else */
 #endif				/* FORTRAN_HAS_NO_SHORT */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 #ifdef HDF
     if ((nc_type) datatype == NC_LONG && handle->file_type!=HDF_FILE) {
 /* EIP  We need to use int buffer to read data in on the platforms where long is 8 bytes
diff --git a/mfhdf/libsrc/array.c b/mfhdf/libsrc/array.c
index 4e97578..ec311be 100644
--- a/mfhdf/libsrc/array.c
+++ b/mfhdf/libsrc/array.c
@@ -625,7 +625,7 @@ xdr_NC_array(xdrs, app)
 		xdr_NC_fnct = xdr_shorts ;
 		goto func ;
 	case NC_LONG :
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 		xdr_NC_fnct = xdr_int ;
 #else
 		xdr_NC_fnct = xdr_long ;
diff --git a/mfhdf/libsrc/cdf.c b/mfhdf/libsrc/cdf.c
index bf6f7b3..847b32f 100644
--- a/mfhdf/libsrc/cdf.c
+++ b/mfhdf/libsrc/cdf.c
@@ -3686,7 +3686,7 @@ NC_var *vp ;
         break ;
     case NC_LONG :
         alen /= 4 ;
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
         xdr_NC_fnct = xdr_int ;
 #else
         xdr_NC_fnct = xdr_long ;
diff --git a/mfhdf/libsrc/netcdf.h.in b/mfhdf/libsrc/netcdf.h.in
index 2e5fb48..66bf27d 100644
--- a/mfhdf/libsrc/netcdf.h.in
+++ b/mfhdf/libsrc/netcdf.h.in
@@ -293,7 +293,7 @@ typedef double        ncdouble;
 /* 
  * Variables/attributes of type NC_LONG should use the C type 'nclong'
  */
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 /*
  * LP64 (also known as 4/8/8) denotes long and pointer as 64 bit types.
  * http://www.unix.org/version2/whatsnew/lp64_wp.html
diff --git a/mfhdf/libsrc/putget.c b/mfhdf/libsrc/putget.c
index 7e24686..b55eb61 100644
--- a/mfhdf/libsrc/putget.c
+++ b/mfhdf/libsrc/putget.c
@@ -664,7 +664,7 @@ Void *values ;
 	case NC_SHORT :
 		return( xdr_NCvshort(xdrs, (unsigned)rem/2, (short *)values) ) ;
 	case NC_LONG :
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 		return( xdr_int(xdrs, (nclong *)values) ) ;
 #else
 		return( xdr_long(xdrs, (nclong *)values) ) ;
@@ -1975,7 +1975,7 @@ Void *values ;
 		} /* else */
 		return(TRUE) ;
 	case NC_LONG :
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 		xdr_NC_fnct = xdr_int ;
 #else
 		xdr_NC_fnct = xdr_long ;
diff --git a/mfhdf/libsrc/xdrposix.c b/mfhdf/libsrc/xdrposix.c
index 91802c1..4cbb5b2 100644
--- a/mfhdf/libsrc/xdrposix.c
+++ b/mfhdf/libsrc/xdrposix.c
@@ -254,7 +254,7 @@ int nbytes;
 
 static bool_t   xdrposix_getlong();
 static bool_t   xdrposix_putlong();
-#if (_MIPS_SZLONG == 64) || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if (_MIPS_SZLONG == 64) || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 static bool_t   xdrposix_getint();
 static bool_t   xdrposix_putint();
 #endif
@@ -268,7 +268,7 @@ static long *    xdrposix_inline();
 #if (defined __sun && defined _LP64)
 static rpc_inline_t *    xdrposix_inline();
 #else
-#if ((defined __x86_64__ ) && !(defined __sun && defined _LP64)) || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if ((defined __x86_64__ ) && !(defined __sun && defined _LP64)) || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 static int32_t *    xdrposix_inline();
 #else
 #if (defined __alpha )
@@ -298,9 +298,9 @@ static struct xdr_ops   xdrposix_ops = {
     xdrposix_getpos,    /* get offset in the stream */
     xdrposix_setpos,    /* set offset in the stream */
     xdrposix_inline,    /* prime stream for inline macros */
-#if (defined __sun && defined _LP64) || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if (defined __sun && defined _LP64) || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
     xdrposix_destroy,   /* destroy stream */
-#if !(defined __aarch64__) && !(defined __s390x__) && !(defined __x86_64__) && !(defined __powerpc64__) || (defined  __sun && defined _LP64) /* i.e. we are on SUN/Intel in 64-bit mode */
+#if !(defined __riscv) && !(defined __aarch64__) && !(defined __s390x__) && !(defined __x86_64__) && !(defined __powerpc64__) || (defined  __sun && defined _LP64) /* i.e. we are on SUN/Intel in 64-bit mode */
     NULL,               /* no xdr_control function defined */
 #endif 
     /* Solaris 64-bit (arch=v9 and arch=amd64) has 64 bits long and 32 bits int. */
@@ -556,7 +556,7 @@ static rpc_inline_t *
 #if (defined  __alpha)
 static int* 
 #else
-#if ((defined  __x86_64__) && !(defined __sun && defined _LP64)) || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if ((defined  __x86_64__) && !(defined __sun && defined _LP64)) || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 static int32_t * 
 #else
 static netlong * 
@@ -584,7 +584,7 @@ int
     return (NULL);
 }
 
-#if (_MIPS_SZLONG == 64) || (defined __sun && defined _LP64) || defined AIX5L64  || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if (_MIPS_SZLONG == 64) || (defined __sun && defined _LP64) || defined AIX5L64  || defined __x86_64__ || defined __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 
 static bool_t
 xdrposix_getint(xdrs, lp)
diff --git a/mfhdf/ncgen/ncgen.l b/mfhdf/ncgen/ncgen.l
index f23bdf6..00edee8 100644
--- a/mfhdf/ncgen/ncgen.l
+++ b/mfhdf/ncgen/ncgen.l
@@ -113,7 +113,7 @@ FloatInf|Infinity|Inf	{    /* float missing values */
 		    yyerror(errstr);
 		}
 
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || __powerpc64__ || defined __s390x__ || defined __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || __powerpc64__ || defined __s390x__ || defined __aarch64__ || (__riscv_xlen == 64)
 		if (dd < INT_MIN  ||  dd > INT_MAX) 
 #else
 		if (dd < LONG_MIN  ||  dd > LONG_MAX) 
diff --git a/mfhdf/ncgen/ncgenyy.c b/mfhdf/ncgen/ncgenyy.c
index 22dcf2f..d4c52fc 100644
--- a/mfhdf/ncgen/ncgenyy.c
+++ b/mfhdf/ncgen/ncgenyy.c
@@ -989,7 +989,7 @@ YY_RULE_SETUP
 		    yyerror(errstr);
 		}
 
-#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || __powerpc64__ || __s390x__ || __aarch64__
+#if defined __alpha || (_MIPS_SZLONG == 64) || defined __ia64 || (defined __sun && defined _LP64) || defined AIX5L64 || defined __x86_64__ || __powerpc64__ || __s390x__ || __aarch64__ || (__riscv_xlen == 64)
 		if (dd < INT_MIN  ||  dd > INT_MAX) 
 #else
 		if (dd < LONG_MIN  ||  dd > LONG_MAX)