Port --enable-gcc-warnings to clang.

* configure.ac (nw): Remove obsolescent warnings.
These aren't needed for clang, or for gcc for that matter.
(emacs_cv_clang): New var, which tests for clang.
Omit warnings that clang is too picky about.
(GLIB_DISABLE_DEPRECATION_WARNINGS): Define this;
needed for Ubuntu 13.04 + clang + --enable-gcc-warnings.
* lib-src/etags.c: Omit unnecessary forward decls.
(print_version, print_help): Declare _Noreturn.
* lib-src/pop.c (socket_connection) [HAVE_GETADDRINFO]: Simplify.
* src/bytecode.c (exec_byte_code):
* src/regex.c:
Redo diagnostic pragmas to pacify clang, too.
* src/dbusbind.c (xd_retrieve_arg): Do not use uninitialized variable.
* src/editfns.c (Fencode_time):
* src/fileio.c (file_accessible_directory_p):
* src/font.c (font_unparse_xlfd):
Use '&"string"[index]' instead of '"string" + (index)'.
* src/undo.c (user_error): Remove; unused.

8 files changed, 28 insertions, 15 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 6909367dccb..e1f7a56aede 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,16 @@
+2013-05-18  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Port --enable-gcc-warnings to clang.
+        * bytecode.c (exec_byte_code):
+        * regex.c:
+        Redo diagnostic pragmas to pacify clang, too.
+        * dbusbind.c (xd_retrieve_arg): Do not use uninitialized variable.
+        * editfns.c (Fencode_time):
+        * fileio.c (file_accessible_directory_p):
+        * font.c (font_unparse_xlfd):
+        Use '&"string"[index]' instead of '"string" + (index)'.
+        * undo.c (user_error): Remove; unused.
+
 2013-05-16  Eli Zaretskii  <eliz@gnu.org>
 
         * insdel.c (insert_1_both): Document the arguments, instead of
diff --git a/src/bytecode.c b/src/bytecode.c
index 7676c8550a4..4940fd5c182 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -660,9 +660,12 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
          the table clearer.  */
 #define LABEL(OP) [OP] = &&insn_ ## OP
 
-#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#if 4 < __GNUC__ + (6 <= __GNUC_MINOR__)
 # pragma GCC diagnostic push
 # pragma GCC diagnostic ignored "-Woverride-init"
+#elif defined __clang__
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Winitializer-overrides"
 #endif
 
       /* This is the dispatch table for the threaded interpreter.  */
@@ -676,7 +679,7 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
 #undef DEFINE
         };
 
-#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#if 4 < __GNUC__ + (6 <= __GNUC_MINOR__) || defined __clang__
 # pragma GCC diagnostic pop
 #endif
 
diff --git a/src/dbusbind.c b/src/dbusbind.c
index 863f7634eb5..3ec3c28431b 100644
--- a/src/dbusbind.c
+++ b/src/dbusbind.c
@@ -882,7 +882,7 @@ xd_retrieve_arg (int dtype, DBusMessageIter *iter)
 #endif
       {
         dbus_uint32_t val;
-        unsigned int pval = val;
+        unsigned int pval;
         dbus_message_iter_get_basic (iter, &val);
         pval = val;
         XD_DEBUG_MESSAGE ("%c %u", dtype, pval);
diff --git a/src/editfns.c b/src/editfns.c
index e0b0347fe69..cc6b4cff895 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -1946,7 +1946,7 @@ usage: (encode-time SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE)  */)
           EMACS_INT zone_hr = abszone / (60*60);
           int zone_min = (abszone/60) % 60;
           int zone_sec = abszone % 60;
-          sprintf (tzbuf, tzbuf_format, "-" + (XINT (zone) < 0),
+          sprintf (tzbuf, tzbuf_format, &"-"[XINT (zone) < 0],
                    zone_hr, zone_min, zone_sec);
           tzstring = tzbuf;
         }
diff --git a/src/fileio.c b/src/fileio.c
index fe1bce16ca0..f20721251e6 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -2873,7 +2873,7 @@ file_accessible_directory_p (char const *file)
          and it's a safe optimization here.  */
       char *buf = SAFE_ALLOCA (len + 3);
       memcpy (buf, file, len);
-      strcpy (buf + len, "/." + (file[len - 1] == '/'));
+      strcpy (buf + len, &"/."[file[len - 1] == '/']);
       dir = buf;
     }
 
diff --git a/src/font.c b/src/font.c
index ad601177b50..7bd44a5e52f 100644
--- a/src/font.c
+++ b/src/font.c
@@ -1219,7 +1219,7 @@ font_unparse_xlfd (Lisp_Object font, int pixel_size, char *name, int nbytes)
                 return -1;
               f[j] = p = alloca (alloc);
               sprintf (p, "%s%s-*", SDATA (val),
-                       "*" + (SDATA (val)[SBYTES (val) - 1] == '*'));
+                       &"*"[SDATA (val)[SBYTES (val) - 1] == '*']);
             }
           else
             f[j] = SSDATA (val);
@@ -1618,7 +1618,7 @@ font_unparse_fcname (Lisp_Object font, int pixel_size, char *name, int nbytes)
     }
   if (point_size > 0)
     {
-      int len = snprintf (p, lim - p, "-%d" + (p == name), point_size);
+      int len = snprintf (p, lim - p, &"-%d"[p == name], point_size);
       if (! (0 <= len && len < lim - p))
         return -1;
       p += len;
diff --git a/src/regex.c b/src/regex.c
index 04429386f84..79fb28ba12a 100644
--- a/src/regex.c
+++ b/src/regex.c
@@ -33,10 +33,9 @@
 
 /* Ignore some GCC warnings for now.  This section should go away
    once the Emacs and Gnulib regex code is merged.  */
-#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
+#if 4 < __GNUC__ + (5 <= __GNUC_MINOR__) || defined __clang__
 # pragma GCC diagnostic ignored "-Wstrict-overflow"
 # ifndef emacs
-#  pragma GCC diagnostic ignored "-Wunused-but-set-variable"
 #  pragma GCC diagnostic ignored "-Wunused-function"
 #  pragma GCC diagnostic ignored "-Wunused-macros"
 #  pragma GCC diagnostic ignored "-Wunused-result"
@@ -44,6 +43,10 @@
 # endif
 #endif
 
+#if 4 < __GNUC__ + (5 <= __GNUC_MINOR__) && ! defined __clang__
+# pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+#endif
+
 #include <config.h>
 
 #include <stddef.h>
diff --git a/src/undo.c b/src/undo.c
index 63edc8e9b8d..d8711882fbf 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -445,12 +445,6 @@ truncate_undo_list (struct buffer *b)
   unbind_to (count, Qnil);
 }
 
-static _Noreturn void
-user_error (const char *msg)
-{
-  xsignal1 (Quser_error, build_string (msg));
-}
-
 
 void
 syms_of_undo (void)