display.c:

- 'savech' is only used if it is set a few lines above where
	  it is used, initialize it to silence warning.

	- 'length' is either -1 or greater than 0, hence it is safe to cast it
	  to unsigned when comparing it here.

odsyntax.c:
	- 'p' is assigned either (*argvp)[0] or (*argvp)[1] which both are
	  char *. 'num' and 'end' are assigned values based on 'p'.
	  Hence use char * instead of unsigned char * for these variables.

	  '&end' as the second argument to strtoll does not need to be casted
	  to char** any more.

	  This solves a
	  'dereferencing type-punned pointer will break strict-aliasing rules'
	  warning when compiling with -O2.

parse.c:
	- 'prec' is only used when sokay == USEPREC and sokay = USEPREC
	  when 'prec' is assigned. Hence 'prec' is not used uninitialized,
	  initialize it to silence warning.

	- The code involving 'nextpr' is hard to follow, but I belive
	  'nextpr' will not be used unless it is initialized.
	  Anyway, IF 'nextpr' is used uninitialized it is better to
	  get a consistant error (seg fault, when dereferencing a NULL pointer)
	  than potentially accessing some random memory.

The above changes makes hexdump WARNS=6 clean even when compiled with
-O2. Hence bump WARNS to keep it clean.

Tested by:	CFLAGS='-O2 -pipe' make universe

usr.bin/hexdump/Makefile

@@ -7,5 +7,6 @@ MAN=	hexdump.1 od.1
 MLINKS=	hexdump.1 hd.1
 LINKS=	${BINDIR}/hexdump ${BINDIR}/od
 LINKS+=	${BINDIR}/hexdump ${BINDIR}/hd
+WARNS?=	6
 
 .include <bsd.prog.mk>

usr.bin/hexdump/display.c

@@ -68,6 +68,7 @@ display(void)
 	off_t saveaddress;
 	u_char savech, *savebp;
 
+	savech = 0;
 	while ((bp = get()))
 	    for (fs = fshead, savebp = bp, saveaddress = address; fs;
 		fs = fs->nextfs, bp = savebp, address = saveaddress)
@@ -318,7 +319,7 @@ peek(u_char *buf, size_t nbytes)
 	size_t n, nread;
 	int c;
 
-	if (length != -1 && nbytes > length)
+	if (length != -1 && nbytes > (unsigned int)length)
 		nbytes = length;
 	nread = 0;
 	while (nread < nbytes && (c = getchar()) != EOF) {

usr.bin/hexdump/odsyntax.c

@@ -193,7 +193,7 @@ odusage(void)
 static void
 odoffset(int argc, char ***argvp)
 {
-	unsigned char *p, *num, *end;
+	char *p, *num, *end;
 	int base;
 
 	/*
@@ -246,7 +246,7 @@ odoffset(int argc, char ***argvp)
 		base = 10;
 	}
 
-	skip = strtoll(num, (char **)&end, base ? base : 8);
+	skip = strtoll(num, &end, base ? base : 8);
 
 	/* if end isn't the same as p, we got a non-octal digit */
 	if (end != p) {

usr.bin/hexdump/parse.c

@@ -214,6 +214,9 @@ rewrite(FS *fs)
 	char savech, cs[3];
 	int nconv, prec;
 
+	nextpr = NULL;
+	prec = 0;
+
 	for (fu = fs->nextfu; fu; fu = fu->nextfu) {
 		/*
 		 * Break each format unit into print units; each conversion