maint: avoid -Werror=strict-overflow warnings with GCC 5

All warnings were of the form: "assuming signed overflow does not occur
when simplifying conditional to constant [-Werror=strict-overflow]"

* src/dd.c (cache_round): Use an appropriately sized unsigned type,
to avoid possibility of undefined signed overflow.
* src/mknod.c (main): Likewise.
* src/pr.c (pad_down): Likewise.
* src/wc.c (main): Likewise.
* src/tail.c (main): Assert that argc >= 0 thus allowing the
compiler to assume without implication that argc - optind
is positive.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/dd.c b/src/dd.c
index e78f2a290..321b096d4 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -987,7 +987,7 @@ cache_round (int fd, off_t len)
 
   if (len)
     {
-      off_t c_pending = *pending + len;
+      uintmax_t c_pending = *pending + len;
       *pending = c_pending % page_size;
       if (c_pending > *pending)
         len = c_pending - *pending;