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].

5 files changed, 38 insertions, 32 deletions

diff --git a/src/expr.c b/src/expr.c
index b4fa808a0..9d21ca87f 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -44,8 +44,6 @@
    int, the widest unsigned type that GMP supports.  */
 verify (SIZE_MAX <= ULONG_MAX);
 
-static void integer_overflow (char) ATTRIBUTE_NORETURN;
-
 #ifndef HAVE_GMP
 # define HAVE_GMP 0
 #endif
@@ -53,6 +51,7 @@ static void integer_overflow (char) ATTRIBUTE_NORETURN;
 #if HAVE_GMP
 # include <gmp.h>
 #else
+static void integer_overflow (char) ATTRIBUTE_NORETURN;
 /* Approximate gmp.h well enough for expr.c's purposes.  */
 typedef intmax_t mpz_t[1];
 static void mpz_clear (mpz_t z) { (void) z; }
@@ -278,6 +277,7 @@ syntax_error (void)
   error (EXPR_INVALID, 0, _("syntax error"));
 }
 
+#if ! HAVE_GMP
 /* Report an integer overflow for operation OP and exit.  */
 static void
 integer_overflow (char op)
@@ -285,15 +285,7 @@ integer_overflow (char op)
   error (EXPR_FAILURE, ERANGE, "%c", op);
   abort (); /* notreached */
 }
-
-static void die (int errno_val, char const *msg)
-  ATTRIBUTE_NORETURN;
-static void
-die (int errno_val, char const *msg)
-{
-  error (EXPR_FAILURE, errno_val, "%s", msg);
-  abort (); /* notreached */
-}
+#endif
 
 int
 main (int argc, char **argv)
diff --git a/src/ls.c b/src/ls.c
index d9876f842..72aee994f 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -962,25 +962,33 @@ static struct obstack subdired_obstack;
 static struct obstack dev_ino_obstack;
 
 /* Push a pair onto the device/inode stack.  */
-#define DEV_INO_PUSH(Dev, Ino)						\
-  do									\
-    {									\
-      struct dev_ino *di;						\
-      obstack_blank (&dev_ino_obstack, sizeof (struct dev_ino));	\
-      di = -1 + (struct dev_ino *) obstack_next_free (&dev_ino_obstack); \
-      di->st_dev = (Dev);						\
-      di->st_ino = (Ino);						\
-    }									\
-  while (0)
+static void
+dev_ino_push (dev_t dev, ino_t ino)
+{
+  void *vdi;
+  struct dev_ino *di;
+  int dev_ino_size = sizeof *di;
+  obstack_blank (&dev_ino_obstack, dev_ino_size);
+  vdi = obstack_next_free (&dev_ino_obstack);
+  di = vdi;
+  di--;
+  di->st_dev = dev;
+  di->st_ino = ino;
+}
 
 /* Pop a dev/ino struct off the global dev_ino_obstack
    and return that struct.  */
 static struct dev_ino
 dev_ino_pop (void)
 {
-  assert (sizeof (struct dev_ino) <= obstack_object_size (&dev_ino_obstack));
-  obstack_blank (&dev_ino_obstack, -(int) (sizeof (struct dev_ino)));
-  return *(struct dev_ino *) obstack_next_free (&dev_ino_obstack);
+  void *vdi;
+  struct dev_ino *di;
+  int dev_ino_size = sizeof *di;
+  assert (dev_ino_size <= obstack_object_size (&dev_ino_obstack));
+  obstack_blank (&dev_ino_obstack, -dev_ino_size);
+  vdi = obstack_next_free (&dev_ino_obstack);
+  di = vdi;
+  return *di;
 }
 
 /* Note the use commented out below:
@@ -1978,7 +1986,7 @@ decode_switches (int argc, char **argv)
   if (file_type <= indicator_style)
     {
       char const *p;
-      for (p = "*=>@|" + indicator_style - file_type; *p; p++)
+      for (p = &"*=>@|"[indicator_style - file_type]; *p; p++)
         set_char_quoting (filename_quoting_options, *p, 1);
     }
 
@@ -2542,7 +2550,7 @@ print_dir (char const *name, char const *realname, bool command_line_arg)
           return;
         }
 
-      DEV_INO_PUSH (dir_stat.st_dev, dir_stat.st_ino);
+      dev_ino_push (dir_stat.st_dev, dir_stat.st_ino);
     }
 
   if (recursive || print_dir_name)
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
diff --git a/src/system.h b/src/system.h
index 94c968fbd..db8931635 100644
--- a/src/system.h
+++ b/src/system.h
@@ -496,21 +496,24 @@ ptr_align (void const *ptr, size_t alignment)
    Note the word after the buffer must be non NUL. */
 
 static inline bool _GL_ATTRIBUTE_PURE
-is_nul (const char *buf, size_t bufsize)
+is_nul (void const *buf, size_t bufsize)
 {
   typedef uintptr_t word;
+  void const *vp;
+  char const *cbuf = buf;
+  word const *wp = buf;
 
   /* Find first nonzero *word*, or the word with the sentinel.  */
-  word *wp = (word *) buf;
   while (*wp++ == 0)
     continue;
 
   /* Find the first nonzero *byte*, or the sentinel.  */
-  char *cp = (char *) (wp - 1);
+  vp = wp - 1;
+  char const *cp = vp;
   while (*cp++ == 0)
     continue;
 
-  return cp > buf + bufsize;
+  return cbuf + bufsize < cp;
 }
 
 /* If 10*Accum + Digit_val is larger than the maximum value for Type,
diff --git a/src/tail.c b/src/tail.c
index 6bbc7251f..0f1a37c07 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -1446,6 +1446,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files,
     {
       struct File_spec *fspec;
       struct inotify_event *ev;
+      void *void_ev;
 
       /* When following by name without --retry, and the last file has
          been unlinked or renamed-away, diagnose it and return.  */
@@ -1507,7 +1508,8 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files,
             error (EXIT_FAILURE, errno, _("error reading inotify event"));
         }
 
-      ev = (struct inotify_event *) (evbuf + evbuf_off);
+      void_ev = evbuf + evbuf_off;
+      ev = void_ev;
       evbuf_off += sizeof (*ev) + ev->len;
 
       if (ev->len) /* event on ev->name in watched directory  */