diff --git a/edit.c b/edit.c
index 9550924f..0c503285 100644
--- a/edit.c
+++ b/edit.c
@@ -147,7 +147,7 @@ public char * back_textlist(struct textlist *tlist, char *prev)
 /*
  * Parse a single option setting in a modeline.
  */
-static void modeline_option(char *str, int opt_len)
+static void modeline_option(constant char *str, int opt_len)
 {
 	struct mloption { constant char *opt_name; void (*opt_func)(constant char*,int); };
 	struct mloption options[] = {
@@ -171,10 +171,10 @@ static void modeline_option(char *str, int opt_len)
  * String length, terminated by option separator (space or colon).
  * Space/colon can be escaped with backspace.
  */
-static int modeline_option_len(char *str)
+static int modeline_option_len(constant char *str)
 {
 	int esc = FALSE;
-	char *s;
+	constant char *s;
 	for (s = str;  *s != '\0';  s++)
 	{
 		if (esc)
@@ -190,12 +190,12 @@ static int modeline_option_len(char *str)
 /*
  * Parse colon- or space-separated option settings in a modeline.
  */
-static void modeline_options(char *str, char end_char)
+static void modeline_options(constant char *str, char end_char)
 {
 	for (;;)
 	{
 		int opt_len;
-		str = skipsp(str);
+		str = skipspc(str);
 		if (*str == '\0' || *str == end_char)
 			break;
 		opt_len = modeline_option_len(str);
@@ -209,21 +209,21 @@ static void modeline_options(char *str, char end_char)
 /*
  * See if there is a modeline string in a line.
  */
-static void check_modeline(char *line)
+static void check_modeline(constant char *line)
 {
 #if HAVE_STRSTR
-	static char *pgms[] = { "less:", "vim:", "vi:", "ex:", NULL };
-	char **pgm;
+	static constant char *pgms[] = { "less:", "vim:", "vi:", "ex:", NULL };
+	constant char **pgm;
 	for (pgm = pgms;  *pgm != NULL;  ++pgm)
 	{
-		char *pline = line;
+		constant char *pline = line;
 		for (;;)
 		{
-			char *str;
+			constant char *str;
 			pline = strstr(pline, *pgm);
 			if (pline == NULL) /* pgm is not in this line */
 				break;
-			str = skipsp(pline + strlen(*pgm));
+			str = skipspc(pline + strlen(*pgm));
 			if (pline == line || pline[-1] == ' ')
 			{
 				if (strncmp(str, "set ", 4) == 0)
@@ -924,7 +924,7 @@ public void cat_file(void)
  * is standard input, create the log file.  
  * We take care not to blindly overwrite an existing file.
  */
-public void use_logfile(char *filename)
+public void use_logfile(constant char *filename)
 {
 	int exists;
 	int answer;
diff --git a/evar.c b/evar.c
index 9b369e72..27c9edb5 100644
--- a/evar.c
+++ b/evar.c
@@ -161,6 +161,7 @@ static int add_evar(struct xbuffer *xbuf, char *buf, int len, int e, constant ch
 
 /*
  * Expand env variables in a string.
+ * Writes expanded output to xbuf. Corrupts buf.
  */
 public void expand_evars(char *buf, int len, struct xbuffer *xbuf)
 {
diff --git a/line.c b/line.c
index b3408373..e9f7dff1 100644
--- a/line.c
+++ b/line.c
@@ -77,7 +77,7 @@ static int in_hilite;
 
 static int attr_swidth(int a);
 static int attr_ewidth(int a);
-static int do_append(LWCHAR ch, char *rep, POSITION pos);
+static int do_append(LWCHAR ch, constant char *rep, POSITION pos);
 
 extern int sigs;
 extern int bs_mode;
@@ -288,7 +288,7 @@ static void add_linebuf(char ch, int attr, int w)
 /*
  * Append a string to the line buffer.
  */
-static void addstr_linebuf(char *s, int attr, int cw)
+static void addstr_linebuf(constant char *s, int attr, int cw)
 {
 	for ( ;  *s != '\0';  s++)
 		add_linebuf(*s, attr, cw);
@@ -677,7 +677,7 @@ static int fits_on_screen(int w, int a)
 		if (store_char((ch),(a),(rep),(pos))) return (1); \
 	} while (0)
 
-static int store_char(LWCHAR ch, int a, char *rep, POSITION pos)
+static int store_char(LWCHAR ch, int a, constant char *rep, POSITION pos)
 {
 	int w;
 	int i;
@@ -968,7 +968,7 @@ public int pappend(int c, POSITION pos)
 	return (r);
 }
 
-static int store_control_char(LWCHAR ch, char *rep, POSITION pos)
+static int store_control_char(LWCHAR ch, constant char *rep, POSITION pos)
 {
 	if (ctldisp == OPT_ON)
 	{
@@ -982,7 +982,7 @@ static int store_control_char(LWCHAR ch, char *rep, POSITION pos)
 	return (0);
 }
 
-static int store_ansi(LWCHAR ch, char *rep, POSITION pos)
+static int store_ansi(LWCHAR ch, constant char *rep, POSITION pos)
 {
 	switch (ansi_step(line_ansi, ch))
 	{
@@ -1021,7 +1021,7 @@ static int store_ansi(LWCHAR ch, char *rep, POSITION pos)
 	return (0);
 } 
 
-static int store_bs(LWCHAR ch, char *rep, POSITION pos)
+static int store_bs(LWCHAR ch, constant char *rep, POSITION pos)
 {
 	if (proc_backspace == OPT_ONPLUS || (bs_mode == BS_CONTROL && proc_backspace == OPT_OFF))
 		return store_control_char(ch, rep, pos);
@@ -1036,7 +1036,7 @@ static int store_bs(LWCHAR ch, char *rep, POSITION pos)
 	return 0;
 }
 
-static int do_append(LWCHAR ch, char *rep, POSITION pos)
+static int do_append(LWCHAR ch, constant char *rep, POSITION pos)
 {
 	int a = AT_NORMAL;
 	int in_overstrike = overstrike;
@@ -1579,7 +1579,7 @@ static int color_index(int attr)
 /*
  * Set the color string to use for a given attribute.
  */
-public int set_color_map(int attr, char *colorstr)
+public int set_color_map(int attr, constant char *colorstr)
 {
 	int cx = color_index(attr);
 	if (cx < 0)
@@ -1595,7 +1595,7 @@ public int set_color_map(int attr, char *colorstr)
 /*
  * Get the color string to use for a given attribute.
  */
-public char * get_color_map(int attr)
+public constant char * get_color_map(int attr)
 {
 	int cx = color_index(attr);
 	if (cx < 0)
diff --git a/main.c b/main.c
index 87e98260..ec4b680d 100644
--- a/main.c
+++ b/main.c
@@ -508,6 +508,14 @@ public char * skipsp(char *s)
 	return (s);
 }
 
+/* {{ There must be a better way. }} */
+public constant char * skipspc(constant char *s)
+{
+	while (*s == ' ' || *s == '\t')
+		s++;
+	return (s);
+}
+
 /*
  * See how many characters of two strings are identical.
  * If uppercase is true, the first string must begin with an uppercase
diff --git a/screen.c b/screen.c
index 3d73dbd5..17401ac5 100644
--- a/screen.c
+++ b/screen.c
@@ -2455,7 +2455,7 @@ static int parse_color4(char ch)
 /*
  * Parse a color as a decimal integer.
  */
-static int parse_color6(char **ps)
+static int parse_color6(constant char **ps)
 {
 	if (**ps == '-')
 	{
@@ -2463,10 +2463,12 @@ static int parse_color6(char **ps)
 		return CV_NOCHANGE;
 	} else
 	{
-		char *ops = *ps;
-		int color = lstrtoi(ops, ps, 10);
-		if (color < 0 || *ps == ops)
+		char *wps = (char *) *ps;  /*{{const-issue}}*/
+		char *ops = wps;
+		int color = lstrtoi(wps, &wps, 10);
+		if (color < 0 || wps == ops)
 			return CV_ERROR;
+		*ps = (constant char *) wps; /*{{const-issue}}*/
 		return color;
 	}
 }
@@ -2477,7 +2479,7 @@ static int parse_color6(char **ps)
  *  CV_4BIT: fg/bg values are OR of CV_{RGB} bits.
  *  CV_6BIT: fg/bg values are integers entered by user.
  */
-public COLOR_TYPE parse_color(char *str, int *p_fg, int *p_bg)
+public COLOR_TYPE parse_color(constant char *str, int *p_fg, int *p_bg)
 {
 	int fg;
 	int bg;
@@ -2542,7 +2544,7 @@ static void tput_fmt(char *fmt, int color, int (*f_putc)(int))
 	attrcolor = color;
 }
 
-static void tput_color(char *str, int (*f_putc)(int))
+static void tput_color(constant char *str, int (*f_putc)(int))
 {
 	int fg;
 	int bg;
@@ -2574,7 +2576,7 @@ static void tput_color(char *str, int (*f_putc)(int))
 
 static void tput_inmode(char *mode_str, int attr, int attr_bit, int (*f_putc)(int))
 {
-	char *color_str;
+	constant char *color_str;
 	if ((attr & attr_bit) == 0)
 		return;
 	color_str = get_color_map(attr_bit);