build: new configure option --enable-gcc-warnings

This has a similar meaning as in other GNU applications
such as coreutils and Emacs.
* NEWS: Document it.
* .gitignore: Remove redundant build-aux.
Remove gnu, since gnu/Makefile.am is now in git.
Add gnu/.gitignore, gnu/charset.alias, gnu/*.h, gnu/*/ to cover
autogenerated files.
* bootstrap.conf (gnulib_mk): Remove.
* configure.ac: Add support for --enable-gcc-warnings,
taken from coreutils and simplified.
* gnu/Makefile.am: New file.  Formerly this was autogenerated,
but the autogenerated file has been renamed to gnulib.mk,
its usual name when bootstrapping from gnulib.
This way, AM_CFLAGS can incorporate warning options.
* gnulib.modules: Add manywarnings.
* lib/Makefile.am, src/Makefile.am (AM_CFLAGS): New macro,
incorporating warning options.
* lib/attr-xattr.in.h (ENOATTR): New macro, if not already defined.
* src/buffer.c (magic): Don't rely on incomplete initializers.
* src/common.h (report_difference): Add printf format attribute.
* src/system.c (sys_exec_command, sys_exec_info_script)
(sys_exec_checkpoint_script):
* src/tar.c (update_argv):
Add casts to char * to pacify GCC warnings about using string
literals in a char * context.
* src/xattrs.c, src/xattrs.h (xattrs_clear_setup):
Declare parameters as (void), not ().
* src/xheader.c (xheader_format_name): Initialize pptr to null,
to pacify GCC.  Remove unnecessary test of nptr versus null.

src/Makefile.am

@@ -46,6 +46,7 @@ tar_SOURCES = \
  xattrs.c
 
 AM_CPPFLAGS = -I$(top_srcdir)/gnu -I../ -I../gnu -I$(top_srcdir)/lib -I../lib
+AM_CFLAGS = $(WARN_CFLAGS) $(WERROR_CFLAGS)
 
 LDADD = ../lib/libtar.a ../gnu/libgnu.a $(LIBINTL) $(LIBICONV)
 

src/buffer.c

@@ -289,8 +289,8 @@ struct zip_program
 };
 
 static struct zip_magic const magic[] = {
-  { ct_none, },
-  { ct_tar },
+  { ct_none,     0, 0 },
+  { ct_tar,      0, 0 },
   { ct_compress, 2, "\037\235" },
   { ct_gzip,     2, "\037\213" },
   { ct_bzip2,    3, "BZh" },

src/common.h

@@ -781,7 +781,8 @@ void sys_exec_checkpoint_script (const char *script_name,
 				 int checkpoint_number);
 
 /* Module compare.c */
-void report_difference (struct tar_stat_info *st, const char *message, ...);
+void report_difference (struct tar_stat_info *st, const char *message, ...)
+  __attribute__ ((format (printf, 2, 3)));
 
 /* Module sparse.c */
 bool sparse_member_p (struct tar_stat_info *st);

src/system.c

@@ -722,8 +722,8 @@ sys_exec_command (char *file_name, int typechar, struct tar_stat_info *st)
 
   stat_to_env (file_name, typechar, st);
 
-  argv[0] = "/bin/sh";
-  argv[1] = "-c";
+  argv[0] = (char *) "/bin/sh";
+  argv[1] = (char *) "-c";
   argv[2] = to_command_option;
   argv[3] = NULL;
 
@@ -837,8 +837,8 @@ sys_exec_info_script (const char **archive_name, int volume_number)
 
   xclose (p[PREAD]);
 
-  argv[0] = "/bin/sh";
-  argv[1] = "-c";
+  argv[0] = (char *) "/bin/sh";
+  argv[1] = (char *) "-c";
   argv[2] = (char *) info_script_option;
   argv[3] = NULL;
 
@@ -885,8 +885,8 @@ sys_exec_checkpoint_script (const char *script_name,
   setenv ("TAR_FORMAT",
 	  archive_format_string (current_format == DEFAULT_FORMAT ?
 				 archive_format : current_format), 1);
-  argv[0] = "/bin/sh";
-  argv[1] = "-c";
+  argv[0] = (char *) "/bin/sh";
+  argv[1] = (char *) "-c";
   argv[2] = (char *) script_name;
   argv[3] = NULL;
 

src/tar.c

@@ -1287,7 +1287,7 @@ update_argv (const char *filename, struct argp_state *state)
   for (i = state->next, p = start; *p; p += strlen (p) + 1, i++)
     {
       if (term == 0 && p[0] == '-')
-	state->argv[i++] = "--add-file";
+	state->argv[i++] = (char *) "--add-file";
       state->argv[i] = p;
     }
 }
@@ -2013,7 +2013,7 @@ parse_opt (int key, char *arg, struct argp_state *state)
     case OLD_ARCHIVE_OPTION:
       set_archive_format ("v7");
       break;
-      
+
     case OVERWRITE_DIR_OPTION:
       old_files_option = DEFAULT_OLD_FILES;
       break;

src/xattrs.c

@@ -137,7 +137,7 @@ static char *
 skip_to_ext_fields (char *ptr)
 {
   /* skip tag name (user/group/default/mask) */
-  ptr += strcspn (ptr, ":,\n"); 
+  ptr += strcspn (ptr, ":,\n");
 
   if (*ptr != ':')
     return ptr;
@@ -192,7 +192,7 @@ static void
 xattrs__acls_set (struct tar_stat_info const *st,
                   char const *file_name, int type,
                   char *ptr, size_t len, bool def)
-{  
+{
   acl_t acl;
 
   if (ptr)
@@ -229,7 +229,7 @@ static void
 xattrs__acls_get_a (int parentfd, const char *file_name,
                     struct tar_stat_info *st,
                     char **ret_ptr, size_t * ret_len)
-{             
+{
   char *val = NULL;
   ssize_t len;
   acl_t acl;
@@ -261,7 +261,7 @@ static void
 xattrs__acls_get_d (int parentfd, char const *file_name,
                     struct tar_stat_info *st,
                     char **ret_ptr, size_t * ret_len)
-{         
+{
   char *val = NULL;
   ssize_t len;
   acl_t acl;
@@ -407,7 +407,7 @@ clear_mask_map (struct xattrs_mask_map *mask_map)
 }
 
 void
-xattrs_clear_setup ()
+xattrs_clear_setup (void)
 {
   clear_mask_map (&xattrs_setup.incl);
   clear_mask_map (&xattrs_setup.excl);
@@ -614,7 +614,7 @@ static bool
 xattrs_masked_out (const char *kw, bool archiving)
 {
   return xattrs_kw_included (kw, archiving) ?
-    xattrs_kw_excluded (kw, archiving) : true; 
+    xattrs_kw_excluded (kw, archiving) : true;
 }
 
 void
@@ -720,7 +720,7 @@ xattrs_print (struct tar_stat_info const *st)
   if (xattrs_option && st->xattr_map_size)
     {
       int i;
-      
+
       for (i = 0; i < st->xattr_map_size; ++i)
         {
           char *keyword = st->xattr_map[i].xkey + strlen ("SCHILY.xattr.");

src/xattrs.h

@@ -28,7 +28,7 @@
 extern void xattrs_mask_add (const char *mask, bool incl);
 
 /* clear helping structures when tar finishes */
-extern void xattrs_clear_setup ();
+extern void xattrs_clear_setup (void);
 
 extern void xattrs_acls_get (int parentfd, char const *file_name,
                              struct tar_stat_info *st, int fd, int xisfile);

src/xheader.c

@@ -262,7 +262,7 @@ xheader_format_name (struct tar_stat_info *st, const char *fmt, size_t n)
   char *dir = NULL;
   char *base = NULL;
   char pidbuf[UINTMAX_STRSIZE_BOUND];
-  char const *pptr;
+  char const *pptr = NULL;
   char nbuf[UINTMAX_STRSIZE_BOUND];
   char const *nptr = NULL;
 
@@ -335,13 +335,10 @@ xheader_format_name (struct tar_stat_info *st, const char *fmt, size_t n)
 	      break;
 
 	    case 'n':
-	      if (nptr)
-		{
-		  q = stpcpy (q, nptr);
-		  p += 2;
-		  break;
-		}
-	      /* else fall through */
+	      q = stpcpy (q, nptr);
+	      p += 2;
+	      break;
+
 
 	    default:
 	      *q++ = *p++;