diff --git a/src/common/byteswap.c b/src/common/byteswap.c
index 35567fb10..6ef7b1fe6 100644
--- a/src/common/byteswap.c
+++ b/src/common/byteswap.c
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: byteswap.c,v 3.1 2006/12/23 17:27:45 greg Exp $";
+static const char RCSid[] = "$Id: byteswap.c,v 3.2 2021/01/15 18:31:38 greg Exp $";
 #endif
 /*
  * Byte swapping routines
@@ -12,11 +12,11 @@ static const char RCSid[] = "$Id: byteswap.c,v 3.1 2006/12/23 17:27:45 greg Exp
 
 void
 swap16(		/* swap n 16-bit words */
-	register char  *wp,
-	int  n
+	char  *wp,
+	size_t  n
 )
 {
-	register int	t;
+	int	t;
 
 	while (n-- > 0) {
 		t = wp[0]; wp[0] = wp[1]; wp[1] = t;
@@ -27,11 +27,11 @@ swap16(		/* swap n 16-bit words */
 
 void
 swap32(		/* swap n 32-bit words */
-	register char  *wp,
-	int  n
+	char  *wp,
+	size_t  n
 )
 {
-	register int	t;
+	int	t;
 
 	while (n-- > 0) {
 		t = wp[0]; wp[0] = wp[3]; wp[3] = t;
@@ -43,11 +43,11 @@ swap32(		/* swap n 32-bit words */
 
 void
 swap64(		/* swap n 64-bit words */
-	register char  *wp,
-	int  n
+	char  *wp,
+	size_t  n
 )
 {
-	register int	t;
+	int	t;
 
 	while (n-- > 0) {
 		t = wp[0]; wp[0] = wp[7]; wp[7] = t;
diff --git a/src/common/portio.c b/src/common/portio.c
index c631293fc..a00d1f337 100644
--- a/src/common/portio.c
+++ b/src/common/portio.c
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: portio.c,v 2.22 2019/07/15 21:27:25 greg Exp $";
+static const char	RCSid[] = "$Id: portio.c,v 2.23 2021/01/15 18:31:38 greg Exp $";
 #endif
 /*
  * Portable i/o for binary files
@@ -62,15 +62,15 @@ putflt(				/* put out floating point number */
 }
 
 
-int
+size_t
 putbinary(			/* fwrite() replacement for small objects */
 	const void *p,
-	int elsiz,
-	int nel,
+	size_t elsiz,
+	size_t nel,
 	FILE *fp)
 {
 	const char	*s = (const char *)p;
-	int		nbytes = elsiz*nel;
+	size_t		nbytes = elsiz*nel;
 
 	if (nbytes > 128)
 		return(fwrite(p, elsiz, nel, fp));
@@ -143,15 +143,15 @@ getflt(				/* get a floating point number */
 }
 
 
-int
+size_t
 getbinary(			/* fread() replacement for small objects */
 	void *p,
-	int elsiz,
-	int nel,
+	size_t elsiz,
+	size_t nel,
 	FILE *fp)
 {
 	char	*s = (char *)p;
-	int	nbytes = elsiz*nel;
+	size_t	nbytes = elsiz*nel;
 	int	c;
 
 	if (nbytes > 128)
diff --git a/src/common/rtio.h b/src/common/rtio.h
index d1e922ef3..56c4da6fa 100644
--- a/src/common/rtio.h
+++ b/src/common/rtio.h
@@ -1,4 +1,4 @@
-/* RCSid $Id: rtio.h,v 3.23 2019/11/07 23:20:28 greg Exp $ */
+/* RCSid $Id: rtio.h,v 3.24 2021/01/15 18:31:38 greg Exp $ */
 /*
  *	Radiance i/o and string routines
  */
@@ -89,18 +89,18 @@ extern char	*gethomedir(char *uname, char *path, int plen);
 					/* defined in getpath.c */
 extern char	*getpath(char *fname, char *searchpath, int mode);
 					/* defined in byteswap.c */
-extern void	swap16(char *wp, int n);
-extern void	swap32(char *wp, int n);
-extern void	swap64(char *wp, int n);
+extern void	swap16(char *wp, size_t n);
+extern void	swap32(char *wp, size_t n);
+extern void	swap64(char *wp, size_t n);
 					/* defined in portio.c */
 extern void	putstr(char *s, FILE *fp);
 extern void	putint(long i, int siz, FILE *fp);
 extern void	putflt(double f, FILE *fp);
-extern int	putbinary(const void *s, int elsiz, int nel, FILE *fp);
+extern size_t	putbinary(const void *s, size_t elsiz, size_t nel, FILE *fp);
 extern char	*getstr(char *s, FILE *fp);
 extern long	getint(int siz, FILE *fp);
 extern double	getflt(FILE *fp);
-extern int	getbinary(void *s, int elsiz, int nel, FILE *fp);
+extern size_t	getbinary(void *s, size_t elsiz, size_t nel, FILE *fp);
 					/* defined in rexpr.c */
 extern int	ecompile(char *sp, int iflg, int wflag);
 extern char	*expsave(void);
diff --git a/src/util/cmatrix.c b/src/util/cmatrix.c
index b4013ad17..30f71ed00 100644
--- a/src/util/cmatrix.c
+++ b/src/util/cmatrix.c
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: cmatrix.c,v 2.30 2021/01/15 17:22:23 greg Exp $";
+static const char RCSid[] = "$Id: cmatrix.c,v 2.31 2021/01/15 18:31:38 greg Exp $";
 #endif
 /*
  * Color matrix routines.
@@ -309,14 +309,14 @@ cm_load(const char *inspec, int nrows, int ncols, int dtype)
 			}
 	} else {					/* read binary file */
 		if (sizeof(COLOR) == cm_elem_size[dtype]) {
-			int	nread = 0;
+			size_t	nread = 0;
 			do {				/* read all we can */
 				nread += getbinary(cm->cmem + 3*nread,
 						sizeof(COLOR),
-						cm->nrows*cm->ncols - nread,
+						(size_t)cm->nrows*cm->ncols - nread,
 						fp);
 				if (nrows <= 0) {	/* unknown length */
-					if (nread == cm->nrows*cm->ncols)
+					if (nread == (size_t)cm->nrows*cm->ncols)
 							/* need more space? */
 						cm = cm_resize(cm, cm->nrows+ROWINC);
 					else if (nread && !(nread % cm->ncols))
@@ -324,22 +324,22 @@ cm_load(const char *inspec, int nrows, int ncols, int dtype)
 						cm = cm_resize(cm, nread/cm->ncols);
 					else		/* ended mid-row */
 						goto EOFerror;
-				} else if (nread < cm->nrows*cm->ncols)
+				} else if (nread < (size_t)cm->nrows*cm->ncols)
 					goto EOFerror;
-			} while (nread < cm->nrows*cm->ncols);
+			} while (nread < (size_t)cm->nrows*cm->ncols);
 
 			if (swap) {
 				if (sizeof(COLORV) == 4)
 					swap32((char *)cm->cmem,
-							3*cm->nrows*cm->ncols);
+							3*(size_t)cm->nrows*cm->ncols);
 				else /* sizeof(COLORV) == 8 */
 					swap64((char *)cm->cmem,
-							3*cm->nrows*cm->ncols);
+							3*(size_t)cm->nrows*cm->ncols);
 			}
 		} else if (dtype == DTdouble) {
 			double	dc[3];			/* load from double */
 			COLORV	*cvp = cm->cmem;
-			int	n = nrows*ncols;
+			size_t	n = (size_t)nrows*ncols;
 
 			if (n <= 0)
 				goto not_handled;
@@ -353,7 +353,7 @@ cm_load(const char *inspec, int nrows, int ncols, int dtype)
 		} else /* dtype == DTfloat */ {
 			float	fc[3];			/* load from float */
 			COLORV	*cvp = cm->cmem;
-			int	n = nrows*ncols;
+			size_t	n = (size_t)nrows*ncols;
 
 			if (n <= 0)
 				goto not_handled;