maint: avoid warnings from sparse tool

https://sparse.docs.kernel.org/
Running the tool against unviled the following warnings:

  find/parser.c:328:7: warning: Using plain integer as NULL pointer
  find/parser.c:328:10: warning: Using plain integer as NULL pointer
  find/parser.c:328:13: warning: Using plain integer as NULL pointer
  find/parser.c:466:49: warning: Using plain integer as NULL pointer
  find/parser.c:656:45: warning: Using plain integer as NULL pointer
  find/print.c:1024:30: warning: Using plain integer as NULL pointer
  lib/regexprops.c:531:7: warning: symbol 'options' shadows an earlier one
  lib/regextype.c:48:24: warning: symbol 'regex_map' was not declared. Should it be static?
  locate/locate.c:131:25: warning: symbol 'check_existence' was not declared. Should it be static?
  locate/locate.c:207:12: warning: symbol 'metacharacters' was not declared. Should it be static?
  xargs/xargs.c:902:24: warning: symbol 'state' shadows an earlier one
  xargs/xargs.c:542:23: warning: Using plain integer as NULL pointer

The fixes for these findings are all trivial, so let's apply them.

* find/parser.c (parse_table): Initialize pointer-type members of
the last element with NULL instead of 0.
(get_noop): Compare to NULL as end condition of for-loop.
(find_parser): Likewise.
* find/print.c (do_fprintf): Initialize linkname with NULL instead of 0.
* lib/regexprops.c (describe_all): Rename local variable options
to regopts to avoid name shadowing.
* lib/regextype.c (regex_map): Declare static.
* locate/locate.c (check_existence): Likewise.
(metacharacters): Likewise.
* xargs/xargs.c (main): Set eof_str to NULL instead of 0.

6 files changed, 11 insertions, 11 deletions

diff --git a/find/parser.c b/find/parser.c
index 152f0fcd..c728fd6b 100644
--- a/find/parser.c
+++ b/find/parser.c
@@ -325,7 +325,7 @@ static struct parser_table const parse_table[] =
   {ARG_TEST, "-help",                 parse_help,    NULL},       /* GNU */
   {ARG_TEST, "version",               parse_version, NULL},	  /* GNU */
   {ARG_TEST, "-version",              parse_version, NULL},	  /* GNU */
-  {0, 0, 0, 0}
+  {0, NULL, NULL, NULL}
 };
 
 
@@ -463,7 +463,7 @@ get_noop (void)
   int i;
   if (NULL == noop)
     {
-      for (i = 0; parse_table[i].parser_name != 0; i++)
+      for (i = 0; parse_table[i].parser_name != NULL; i++)
 	{
 	  if (ARG_NOOP ==parse_table[i].type)
 	    {
@@ -653,7 +653,7 @@ find_parser (const char *search_name)
   if (*search_name == '-')
     search_name++;
 
-  for (i = 0; parse_table[i].parser_name != 0; i++)
+  for (i = 0; parse_table[i].parser_name != NULL; i++)
     {
       if (strcmp (parse_table[i].parser_name, search_name) == 0)
 	{
diff --git a/find/print.c b/find/print.c
index 62f7d22b..e7f0ba37 100644
--- a/find/print.c
+++ b/find/print.c
@@ -1021,7 +1021,7 @@ do_fprintf (struct format_val *dest,
           /* sanitised */
 #ifdef S_ISLNK
           {
-            char *linkname = 0;
+            char *linkname = NULL;
 
             if (S_ISLNK (stat_buf->st_mode))
               {
diff --git a/lib/regexprops.c b/lib/regexprops.c
index 7cc49b78..f7adbd3a 100644
--- a/lib/regexprops.c
+++ b/lib/regexprops.c
@@ -528,7 +528,7 @@ describe_all (const char *contextname,
 	      const char *up)
 {
   const char *name, *next, *previous;
-  int options;
+  int regopts;
   int i, parent;
 
   copying ();
@@ -542,7 +542,7 @@ describe_all (const char *contextname,
   previous = "";
 
   for (i=0;
-       options = get_regex_type_flags (i),
+       regopts = get_regex_type_flags (i),
 	 name=get_regex_type_name (i);
        ++i)
     {
@@ -568,7 +568,7 @@ describe_all (const char *contextname,
 	}
       else
 	{
-	  describe_regex_syntax (options);
+	  describe_regex_syntax (regopts);
 	}
       previous = name;
     }
diff --git a/lib/regextype.c b/lib/regextype.c
index c87c5e70..9765b9b2 100644
--- a/lib/regextype.c
+++ b/lib/regextype.c
@@ -45,7 +45,7 @@ struct tagRegexTypeMap
   int  option_val;
 };
 
-struct tagRegexTypeMap regex_map[] =
+static struct tagRegexTypeMap regex_map[] =
   {
    { "findutils-default",     CONTEXT_FINDUTILS, RE_SYNTAX_EMACS|RE_DOT_NEWLINE  },
    { "ed",                    CONTEXT_GENERIC,   RE_SYNTAX_ED                    },
diff --git a/locate/locate.c b/locate/locate.c
index 84705e90..da161ff7 100644
--- a/locate/locate.c
+++ b/locate/locate.c
@@ -128,7 +128,7 @@ enum ExistenceCheckType
   };
 
 /* Check for existence of files before printing them out? */
-enum ExistenceCheckType check_existence = ACCEPT_EITHER;
+static enum ExistenceCheckType check_existence = ACCEPT_EITHER;
 
 static int follow_symlinks = 1;
 
@@ -204,7 +204,7 @@ get_short (FILE *fp)
   return x;
 }
 
-const char * const metacharacters = "*?[]\\";
+static const char * const metacharacters = "*?[]\\";
 
 /* Return nonzero if S contains any shell glob characters.
  */
diff --git a/xargs/xargs.c b/xargs/xargs.c
index eedee2d2..2951b005 100644
--- a/xargs/xargs.c
+++ b/xargs/xargs.c
@@ -539,7 +539,7 @@ main (int argc, char **argv)
 	  if (optarg && (strlen (optarg) > 0))
 	    eof_str = optarg;
 	  else
-	    eof_str = 0;
+	    eof_str = NULL;
 	  break;
 
 	case 'h':