Fix overflow handling in dd(1)

[William Orr]

This diff fixes the overflow handling in dd(1).

Before, if provided an argument of SIZE_T_MAX, dd(1) would exit with

dd: count: Undefined error: 0

since strtoul(3) doesn't set errno when its argument is equal to ULONG_MAX.
Now, dd(1) handles SIZE_T_MAX gracefully.

Index: args.c
===================================================================
RCS file: /cvs/src/bin/dd/args.c,v
retrieving revision 1.25
diff -u -b -w -p -r1.25 args.c
--- args.c      21 May 2014 06:23:02 -0000      1.25
+++ args.c      14 Jun 2014 04:02:51 -0000
@@ -196,8 +196,7 @@ static void
 f_count(char *arg)
 {
 
-       if ((cpy_cnt = get_bsz(arg)) == 0)
-               cpy_cnt = (size_t)-1;
+       cpy_cnt = get_bsz(arg);
 }
 
 static void
@@ -323,8 +322,9 @@ get_bsz(char *val)
        size_t num, t;
        char *expr;
 
+       errno = 0;
        num = strtoul(val, &expr, 0);
-       if (num == SIZE_T_MAX)                  /* Overflow. */
+       if (num == SIZE_T_MAX && errno == ERANGE)               /* Overflow. */
                err(1, "%s", oper);
        if (expr == val)                        /* No digits. */
                errx(1, "%s: illegal numeric value", oper);
Index: dd.c
===================================================================
RCS file: /cvs/src/bin/dd/dd.c,v
retrieving revision 1.18
diff -u -b -w -p -r1.18 dd.c
--- dd.c        1 Jun 2013 16:46:49 -0000       1.18
+++ dd.c        14 Jun 2014 04:02:51 -0000
@@ -77,7 +77,7 @@ main(int argc, char *argv[])
 
        atexit(summary);
 
-       if (cpy_cnt != (size_t)-1) {
+       if (cpy_cnt != 0) {
                while (files_cnt--)
                        dd_in();
        }