diff --git a/ch.c b/ch.c
index 5b31204f..fbca8c4a 100644
--- a/ch.c
+++ b/ch.c
@@ -122,7 +122,8 @@ struct filestate {
 	thisfile->hashtbl[h].hnext = (bn);
 
 static struct filestate *thisfile;
-static int ch_ungotchar = -1;
+static unsigned char ch_ungotchar;
+static lbool ch_have_ungotchar = FALSE;
 static int maxbufs = -1;
 
 extern int autobuf;
@@ -260,11 +261,11 @@ static int ch_get(void)
 		 * If we read less than a full block, that's ok.
 		 * We use partial block and pick up the rest next time.
 		 */
-		if (ch_ungotchar != -1)
+		if (ch_have_ungotchar)
 		{
 			bp->data[bp->datasize] = ch_ungotchar;
 			n = 1;
-			ch_ungotchar = -1;
+			ch_have_ungotchar = FALSE;
 		} else if (ch_flags & CH_HELPFILE)
 		{
 			bp->data[bp->datasize] = helpdata[ch_fpos];
@@ -372,9 +373,15 @@ static int ch_get(void)
  */
 public void ch_ungetchar(int c)
 {
-	if (c != -1 && ch_ungotchar != -1)
-		error("ch_ungetchar overrun", NULL_PARG);
-	ch_ungotchar = c;
+	if (c < 0)
+		ch_have_ungotchar = FALSE;
+	else
+	{
+		if (ch_have_ungotchar)
+			error("ch_ungetchar overrun", NULL_PARG);
+		ch_ungotchar = (unsigned char) c;
+		ch_have_ungotchar = TRUE;
+	}
 }
 
 #if LOGFILE
diff --git a/charset.c b/charset.c
index 902e6c3b..136cfd31 100644
--- a/charset.c
+++ b/charset.c
@@ -521,9 +521,10 @@ public int binary_char(LWCHAR c)
 /*
  * Is a given character a "control" character?
  */
-public int control_char(LWCHAR c)
+public lbool control_char(LWCHAR c)
 {
-	c &= 0377;
+	if (!is_ascii_char(c))
+		return FALSE;
 	return (chardef[c] & IS_CONTROL_CHAR);
 }
 
@@ -536,7 +537,7 @@ public constant char * prchar(LWCHAR c)
 	/* {{ This buffer can be overrun if LESSBINFMT is a long string. }} */
 	static char buf[MAX_PRCHAR_LEN+1];
 
-	c &= 0377;
+	c &= 0377; /*{{type-issue}}*/
 	if ((c < 128 || !utf_mode) && !control_char(c))
 		SNPRINTF1(buf, sizeof(buf), "%c", (int) c);
 	else if (c == ESC)
@@ -637,8 +638,7 @@ public lbool is_utf8_well_formed(constant char *ss, int slen)
 			return (FALSE);
 	} else
 	{
-		unsigned char mask;
-		mask = (~((1 << (8-len)) - 1)) & 0xFF;
+		unsigned char mask = (~((((unsigned char)1) << (8-len)) - 1)) & 0xFF;
 		if (s[0] == mask && (s[1] & mask) == 0x80)
 			return (FALSE);
 	}
diff --git a/cmdbuf.c b/cmdbuf.c
index c7b8719c..9c80e3d6 100644
--- a/cmdbuf.c
+++ b/cmdbuf.c
@@ -31,7 +31,8 @@ static int prompt_col;           /* Column of cursor just after prompt */
 static char *cp;                 /* Pointer into cmdbuf */
 static int cmd_offset;           /* Index into cmdbuf of first displayed char */
 static int literal;              /* Next input char should not be interpreted */
-public ssize_t updown_match = -1;    /* Prefix length in up/down movement */
+public size_t updown_match;      /* Prefix length in up/down movement */
+public lbool have_updown_match = FALSE;
 
 #if TAB_COMPLETE_FILENAME
 static int cmd_complete(int action);
@@ -124,7 +125,7 @@ public void cmd_reset(void)
 	cmd_offset = 0;
 	literal = 0;
 	cmd_mbc_buf_len = 0;
-	updown_match = -1;
+	have_updown_match = FALSE;
 }
 
 /*
@@ -134,7 +135,7 @@ public void clear_cmd(void)
 {
 	cmd_col = prompt_col = 0;
 	cmd_mbc_buf_len = 0;
-	updown_match = -1;
+	have_updown_match = FALSE;
 }
 
 /*
@@ -193,7 +194,7 @@ static constant char * cmd_step_common(char *p, LWCHAR ch, size_t len, int *pwid
 
 	if (len == 1)
 	{
-		pr = prchar((int) ch);
+		pr = prchar(ch);
 		width = (int) strlen(pr);
 	} else
 	{
@@ -460,7 +461,7 @@ static int cmd_ichar(constant char *cs, size_t clen)
 	/*
 	 * Reprint the tail of the line from the inserted char.
 	 */
-	updown_match = -1;
+	have_updown_match = FALSE;
 	cmd_repaint(cp);
 	cmd_right();
 	return (CC_OK);
@@ -503,7 +504,7 @@ static int cmd_erase(void)
 	/*
 	 * Repaint the buffer after the erased char.
 	 */
-	updown_match = -1;
+	have_updown_match = FALSE;
 	cmd_repaint(cp);
 	
 	/*
@@ -596,7 +597,7 @@ static int cmd_kill(void)
 	cmd_offset = 0;
 	cmd_home();
 	*cp = '\0';
-	updown_match = -1;
+	have_updown_match = FALSE;
 	cmd_repaint(cp);
 
 	/*
@@ -643,8 +644,11 @@ static int cmd_updown(int action)
 		return (CC_OK);
 	}
 
-	if (updown_match < 0)
+	if (!have_updown_match)
+	{
 		updown_match = ptr_diff(cp, cmdbuf);
+		have_updown_match = TRUE;
+	}
 
 	/*
 	 * Find the next history entry which matches.
diff --git a/command.c b/command.c
index f7e72f84..67c6d2d5 100644
--- a/command.c
+++ b/command.c
@@ -920,8 +920,9 @@ public void dispversion(void)
 /*
  * Return a character to complete a partial command, if possible.
  */
-static LWCHAR getcc_end_command(void)
+static char getcc_end_command(void)
 {
+	int ch;
 	switch (mca)
 	{
 	case A_DIGIT:
@@ -934,7 +935,11 @@ static LWCHAR getcc_end_command(void)
 		return ('\n'); 
 	default:
 		/* Some other incomplete command.  Let user complete it. */
-		return ((ungot == NULL) ? getchr() : 0);
+		if (ungot != NULL)
+			return ('\0');
+		ch = getchr();
+		if (ch < 0) ch = '\0';
+		return (char) ch;
 	}
 }
 
@@ -969,7 +974,7 @@ public void getcc_clear(void)
  */
 static char getccu(void)
 {
-	char c = 0;
+	int c = 0;
 	while (c == 0)
 	{
 		if (ungot == NULL)
@@ -977,6 +982,7 @@ static char getccu(void)
 			/* Normal case: no ungotten chars.
 			 * Get char from the user. */
 			c = getchr();
+			if (c < 0) return ('\0');
 		} else
 		{
 			/* Ungotten chars available:
@@ -998,7 +1004,7 @@ static char getcc_repl(char constant *orig, char constant *repl, char (*gr_getc)
 {
 	char c;
 	char keys[16];
-	int ki = 0;
+	size_t ki = 0;
 
 	c = (*gr_getc)();
 	if (orig == NULL || orig[0] == '\0')
@@ -1033,7 +1039,7 @@ static char getcc_repl(char constant *orig, char constant *repl, char (*gr_getc)
 /*
  * Get command character.
  */
-public LWCHAR getcc(void)
+public char getcc(void)
 {
 	/* Replace kent (keypad Enter) with a newline. */
 	return getcc_repl(kent, "\n", getccu, ungetcc);
diff --git a/cvt.c b/cvt.c
index 04ed303e..0f3a87b1 100644
--- a/cvt.c
+++ b/cvt.c
@@ -82,7 +82,7 @@ public void cvt_text(char *odst, constant char *osrc, int *chpos, size_t *lenp,
 			{
 				if (ansi_step(pansi, ch) != ANSI_MID)
 					break;
-				ch = *src++;
+				ch = (LWCHAR) *src++; /* {{ would step_char work? }} */
 			}
 			ansi_done(pansi);
 		} else
diff --git a/decode.c b/decode.c
index cadb0410..e5206b1f 100644
--- a/decode.c
+++ b/decode.c
@@ -281,7 +281,7 @@ static void expand_special_keys(unsigned char *table, size_t len)
 			if (repl == NULL || strlen(repl) > klen)
 				repl = "\377";
 			while (*repl != '\0')
-				*to++ = *repl++;
+				*to++ = (unsigned char) *repl++; /*{{type-issue}}*/
 		}
 		*to++ = '\0';
 		/*
diff --git a/evar.c b/evar.c
index 33560998..27461163 100644
--- a/evar.c
+++ b/evar.c
@@ -144,14 +144,14 @@ static size_t add_evar(struct xbuffer *xbuf, mutable char *buf, size_t len, size
 	{
 		constant char *repl = find_replace(replaces, evar, &v);
 		if (repl == NULL)
-			xbuf_add_byte(xbuf, evar[v++]);
+			xbuf_add_char(xbuf, evar[v++]);
 		else
 		{
 			size_t r;
 			for (r = 0;  repl[r] != '\0';  r++)
 			{
 				if (repl[r] == '\\') ++r;
-				xbuf_add_byte(xbuf, repl[r]);
+				xbuf_add_char(xbuf, repl[r]);
 			}
 		}
 	}
@@ -186,7 +186,7 @@ public void expand_evars(mutable char *buf, size_t len, struct xbuffer *xbuf)
 			i = add_evar(xbuf, buf, len, e, evar, term);
 		} else
 		{
-			xbuf_add_byte(xbuf, buf[i++]);
+			xbuf_add_char(xbuf, buf[i++]);
 		}
 	}
 }
diff --git a/filename.c b/filename.c
index 0e5763d9..5b0517f7 100644
--- a/filename.c
+++ b/filename.c
@@ -514,7 +514,7 @@ static char * readfd(FILE *fd)
 		int ch;
 		if ((ch = getc(fd)) == '\n' || ch == EOF)
 			break;
-		xbuf_add_char(&xbuf, ch);
+		xbuf_add_char(&xbuf, (char) ch);
 	}
 	xbuf_add_char(&xbuf, '\0');
 	return (char *) xbuf.data;
diff --git a/input.c b/input.c
index d99996de..1ac4a722 100644
--- a/input.c
+++ b/input.c
@@ -151,7 +151,7 @@ public POSITION forw_line_seg(POSITION curr_pos, lbool skipeol, lbool rscroll, l
 			null_line();
 			return (NULL_POSITION);
 		}
-		backchars = pappend(c, new_pos);
+		backchars = pappend((char) c, new_pos);
 		new_pos++;
 		if (backchars > 0)
 		{
@@ -161,7 +161,7 @@ public POSITION forw_line_seg(POSITION curr_pos, lbool skipeol, lbool rscroll, l
 				do
 				{
 					new_pos++;
-					c = ch_forw_get();
+					c = ch_forw_get(); /* {{ what if c == EOI? }} */
 				} while (c == ' ' || c == '\t');
 				backchars = 1;
 			}
@@ -214,7 +214,7 @@ public POSITION forw_line_seg(POSITION curr_pos, lbool skipeol, lbool rscroll, l
 		/*
 		 * Append the char to the line and get the next char.
 		 */
-		backchars = pappend(c, ch_tell()-1);
+		backchars = pappend((char) c, ch_tell()-1);
 		if (backchars > 0)
 		{
 			/*
@@ -250,10 +250,10 @@ public POSITION forw_line_seg(POSITION curr_pos, lbool skipeol, lbool rscroll, l
 						do
 						{
 							new_pos = ch_tell();
-							c = ch_forw_get();
+							c = ch_forw_get(); /* {{ what if c == EOI? }} */
 						} while (c == ' ' || c == '\t');
 						if (c == '\r')
-							c = ch_forw_get();
+							c = ch_forw_get(); /* {{ what if c == EOI? }} */
 						if (c == '\n')
 							new_pos = ch_tell();
 					} else if (wrap_pos == NULL_POSITION)
@@ -373,6 +373,7 @@ public POSITION back_line(POSITION curr_pos)
 		 */
 		(void) ch_forw_get();    /* Skip the newline */
 		c = ch_forw_get();       /* First char of "current" line */
+		/* {{ what if c == EOI? }} */
 		(void) ch_back_get();    /* Restore our position */
 		(void) ch_back_get();
 
@@ -467,7 +468,7 @@ public POSITION back_line(POSITION curr_pos)
 			edisp_pos = new_pos;
 			break;
 		}
-		backchars = pappend(c, ch_tell()-1);
+		backchars = pappend((char) c, ch_tell()-1);
 		if (backchars > 0)
 		{
 			/*
@@ -494,14 +495,14 @@ public POSITION back_line(POSITION curr_pos)
 				{
 					for (;;)
 					{
-						c = ch_forw_get();
+						c = ch_forw_get(); /* {{ what if c == EOI? }} */
 						if (c == ' ' || c == '\t')
 							new_pos++;
 						else
 						{
 							if (c == '\r')
 							{
-								c = ch_forw_get();
+								c = ch_forw_get(); /* {{ what if c == EOI? }} */
 								if (c == '\n')
 									new_pos++;
 							}
diff --git a/less.h b/less.h
index f3e3b050..6afa97e9 100644
--- a/less.h
+++ b/less.h
@@ -77,8 +77,8 @@
  * These substitutes for C23 stdckdint macros do not set *R on overflow,
  * and they assume A and B are nonnegative.  That is good enough for us.
  */
-#define ckd_add(r, a, b) help_ckd_add(r, a, b, sizeof *(r), signed_expr(*(r)))
-#define ckd_mul(r, a, b) help_ckd_mul(r, a, b, sizeof *(r), signed_expr(*(r)))
+#define ckd_add(r, a, b) help_ckd_add(r, (uintmax)(a), (uintmax)(b), sizeof *(r), signed_expr(*(r)))
+#define ckd_mul(r, a, b) help_ckd_mul(r, (uintmax)(a), (uintmax)(b), sizeof *(r), signed_expr(*(r)))
 /* True if the integer expression E, after promotion, is signed.  */
 #define signed_expr(e) ((TRUE ? 0 : e) - 1 < 0)
 #endif
@@ -144,15 +144,15 @@ void free();
 #define TO_LOWER(c)     towlower(c)
 #else
 #if HAVE_UPPER_LOWER
-#define IS_UPPER(c)     isupper((unsigned char) (c))
-#define IS_LOWER(c)     islower((unsigned char) (c))
-#define TO_UPPER(c)     toupper((unsigned char) (c))
-#define TO_LOWER(c)     tolower((unsigned char) (c))
+#define IS_UPPER(c)     (is_ascii_char(c) && isupper((unsigned char) (c)))
+#define IS_LOWER(c)     (is_ascii_char(c) && islower((unsigned char) (c)))
+#define TO_UPPER(c)     (is_ascii_char(c) ? toupper((unsigned char) (c)) : (c))
+#define TO_LOWER(c)     (is_ascii_char(c) ? tolower((unsigned char) (c)) : (c))
 #else
-#define IS_UPPER(c)     ASCII_IS_UPPER(c)
-#define IS_LOWER(c)     ASCII_IS_LOWER(c)
-#define TO_UPPER(c)     ASCII_TO_UPPER(c)
-#define TO_LOWER(c)     ASCII_TO_LOWER(c)
+#define IS_UPPER(c)     (is_ascii_char(c) && ASCII_IS_UPPER(c))
+#define IS_LOWER(c)     (is_ascii_char(c) && ASCII_IS_LOWER(c))
+#define TO_UPPER(c)     (is_ascii_char(c) ? ASCII_TO_UPPER(c) : (c))
+#define TO_LOWER(c)     (is_ascii_char(c) ? ASCII_TO_LOWER(c) : (c))
 #endif
 #endif
 
diff --git a/line.c b/line.c
index 3f887b77..12bb381e 100644
--- a/line.c
+++ b/line.c
@@ -200,7 +200,7 @@ static int expand_linebuf(void)
 /*
  * Is a character ASCII?
  */
-public int is_ascii_char(LWCHAR ch)
+public lbool is_ascii_char(LWCHAR ch)
 {
 	return (ch <= 0x7F);
 }
@@ -381,13 +381,13 @@ public void plinestart(POSITION pos)
  * Return the width of the line prefix (status column and line number).
  * {{ Actual line number can be wider than linenum_width. }}
  */
-public size_t line_pfx_width(void)
+public int line_pfx_width(void)
 {
-	size_t width = 0;
+	int width = 0;
 	if (status_col)
-		width += (size_t) status_col_width; /*{{type-issue}}*/
+		width += status_col_width;
 	if (linenums == OPT_ONPLUS)
-		width += (size_t) linenum_width + 1; /*{{type-issue}}*/
+		width += linenum_width + 1;
 	return width;
 }
 
diff --git a/lsystem.c b/lsystem.c
index 72c86c1c..721f6c11 100644
--- a/lsystem.c
+++ b/lsystem.c
@@ -247,7 +247,7 @@ public void lsystem(constant char *cmd, constant char *donemsg)
  * If the mark is on the current screen, or if the mark is ".",
  * the whole current screen is piped.
  */
-public int pipe_mark(int c, constant char *cmd)
+public int pipe_mark(char c, constant char *cmd)
 {
 	POSITION mpos, tpos, bpos;
 
diff --git a/mark.c b/mark.c
index f257af93..6a10c630 100644
--- a/mark.c
+++ b/mark.c
@@ -311,7 +311,7 @@ public POSITION markpos(char c)
  */
 public char posmark(POSITION pos)
 {
-	int i;
+	unsigned char i;
 
 	/* Only user marks */
 	for (i = 0;  i < NUMARKS;  i++)
diff --git a/option.c b/option.c
index 83e4b8a3..52d015db 100644
--- a/option.c
+++ b/option.c
@@ -48,7 +48,7 @@ static constant char * opt_desc(struct loption *o)
  * Return a string suitable for printing as the "name" of an option.
  * For example, if the option letter is 'x', just return "-x".
  */
-public constant char * propt(int c)
+public constant char * propt(char c)
 {
 	static char buf[MAX_PRCHAR_LEN+2];
 
diff --git a/search.c b/search.c
index 2a433c9d..5c94d654 100644
--- a/search.c
+++ b/search.c
@@ -138,9 +138,9 @@ static lbool is_ucase(constant char *str)
 	{
 		ch = step_charc(&str, +1, str_end);
 		if (IS_UPPER(ch))
-			return (1);
+			return (TRUE);
 	}
-	return (0);
+	return (FALSE);
 }
 
 /*