maint: port --enable-gcc-warnings to clang

* configure.ac: If clang, add -Wno-format-extra-args and
-Wno-tautological-constant-out-of-range-compare.
* gl/lib/rand-isaac.c (ind):
* gl/lib/randread.c (readisaac):
* src/ls.c (dev_ino_push, dev_ino_pop):
* src/sort.c (buffer_linelim):
* src/system.h (is_nul):
* src/tail.c (tail_forever_inotify):
Rewrite to avoid casts that clang dislikes.
It's good to avoid casts anyway.
* src/expr.c (integer_overflow): Declare only if it exists.
(die): Remove; unused.
* src/ls.c (dev_ino_push): New function, replacing ...
(DEV_INO_PUSH): ... this removed macro.  All uses changed.
(decode_switches): Rewrite "str"+i to &str[i].

1 files changed, 2 insertions, 1 deletions

diff --git a/src/sort.c b/src/sort.c
index 7410abca6..062b5f946 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -1557,7 +1557,8 @@ initbuf (struct buffer *buf, size_t line_bytes, size_t alloc)
 static inline struct line *
 buffer_linelim (struct buffer const *buf)
 {
-  return (struct line *) (buf->buf + buf->alloc);
+  void *linelim = buf->buf + buf->alloc;
+  return linelim;
 }
 
 /* Return a pointer to the first character of the field specified