Make use of the NULL macro

Use this constant everywhere when referring to a null pointer instead of
casting 0 to various types of pointers. Created using following semantic
patch:

    @@
    type type;
    @@

    - (type *)0
    + NULL

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/args.c

@@ -906,10 +906,10 @@ parse_args (int argc, char **argv, struct conf *conf)
       else if (gflag)
         {
           io_init (cfile, datadir);
-          io_check_dir (path_dir, (int *)0);
+          io_check_dir (path_dir, NULL);
-          io_check_dir (path_notes, (int *)0);
+          io_check_dir (path_notes, NULL);
-          io_check_file (path_apts, (int *)0);
+          io_check_file (path_apts, NULL);
-          io_check_file (path_todo, (int *)0);
+          io_check_file (path_todo, NULL);
           io_load_app ();
           io_load_todo ();
           note_gc ();
@@ -920,13 +920,13 @@ parse_args (int argc, char **argv, struct conf *conf)
           if (load_data)
             {
               io_init (cfile, datadir);
-              io_check_dir (path_dir, (int *)0);
+              io_check_dir (path_dir, NULL);
-              io_check_dir (path_notes, (int *)0);
+              io_check_dir (path_notes, NULL);
             }
           if (iflag)
             {
-              io_check_file (path_apts, (int *)0);
+              io_check_file (path_apts, NULL);
-              io_check_file (path_todo, (int *)0);
+              io_check_file (path_todo, NULL);
               /* Get default pager in case we need to show a log file. */
               vars_init (conf);
               io_load_app ();
@@ -938,8 +938,8 @@ parse_args (int argc, char **argv, struct conf *conf)
             }
           if (xflag)
             {
-              io_check_file (path_apts, (int *)0);
+              io_check_file (path_apts, NULL);
-              io_check_file (path_todo, (int *)0);
+              io_check_file (path_todo, NULL);
               io_load_app ();
               io_load_todo ();
               io_export_data (xfmt, conf);
@@ -948,22 +948,22 @@ parse_args (int argc, char **argv, struct conf *conf)
             }
           if (tflag)
             {
-              io_check_file (path_todo, (int *)0);
+              io_check_file (path_todo, NULL);
               io_load_todo ();
               todo_arg (tnum, Nflag, preg);
               non_interactive = 1;
             }
           if (nflag)
             {
-              io_check_file (path_apts, (int *)0);
+              io_check_file (path_apts, NULL);
               io_load_app ();
               next_arg ();
               non_interactive = 1;
             }
           if (dflag || rflag || sflag)
             {
-              io_check_file (path_apts, (int *)0);
+              io_check_file (path_apts, NULL);
-              io_check_file (path_conf, (int *)0);
+              io_check_file (path_conf, NULL);
               io_load_app ();
               custom_load_conf (conf); /* To get output date format. */
               if (dflag)
@@ -977,8 +977,8 @@ parse_args (int argc, char **argv, struct conf *conf)
             {
               struct date day;
 
-              io_check_file (path_apts, (int *)0);
+              io_check_file (path_apts, NULL);
-              io_check_file (path_conf, (int *)0);
+              io_check_file (path_conf, NULL);
               vars_init (conf);
               custom_load_conf (conf); /* To get output date format. */
               io_load_app ();

src/calendar.c

@@ -130,7 +130,7 @@ calendar_date_thread (void *arg)
       calendar_update_panel (&win[CAL]);
     }
 
-  return (void *)0;
+  return NULL;
 }
 
 /* Launch the calendar date thread. */

src/custom.c

@@ -572,7 +572,7 @@ custom_layout_config (void)
       "       'a' -> appointment panel\n\n"
       "       't' -> todo panel\n\n");
 
-  conf_win.p = (WINDOW *)0;
+  conf_win.p = NULL;
   strncpy (label, _("layout configuration"), BUFSIZ);
   custom_confwin_init (&conf_win, label);
   cursor = mark = wins_layout () - 1;

src/keys.c

@@ -407,7 +407,7 @@ keys_action_nkey (enum key action, int keynum)
         return key->str;
       i++;
     }
-  return (char *)0;
+  return NULL;
 }
 
 char *
@@ -440,7 +440,7 @@ keys_format_label (char *key, int keylen)
   int i;
 
   if (keylen > BUFSIZ)
-    return (char *)0;
+    return NULL;
 
   bzero (fmtkey, sizeof (fmtkey));
   if (len == 0)

src/mem.c

@@ -176,7 +176,7 @@ dbg_malloc (size_t size, const char *pos)
   unsigned *buf;
 
    if (size == 0)
-    return (void *)0;
+    return NULL;
 
   size = EXTRA_SPACE + (size + sizeof (unsigned) - 1) / sizeof (unsigned);
   buf = xmalloc (size * sizeof (unsigned));
@@ -197,13 +197,13 @@ dbg_calloc (size_t nmemb, size_t size, const char *pos)
   void *buf;
 
   if (!nmemb || !size)
-    return (void *)0;
+    return NULL;
 
   EXIT_IF (nmemb > SIZE_MAX / size, _("overflow at %s"), pos);
 
   size *= nmemb;
   if ((buf = dbg_malloc (size, pos)) == NULL)
-    return (void *)0;
+    return NULL;
 
   bzero (buf, size);
 
@@ -216,16 +216,16 @@ dbg_realloc (void *ptr, size_t nmemb, size_t size, const char *pos)
   unsigned *buf, old_size, new_size, cpy_size;
 
   if (ptr == NULL)
-    return (void *)0;
+    return NULL;
 
   new_size = nmemb *size;
   if (new_size == 0)
-    return (void *)0;
+    return NULL;
 
   EXIT_IF (nmemb > SIZE_MAX / size, _("overflow at %s"), pos);
 
   if ((buf = dbg_malloc (new_size, pos)) == NULL)
-    return (void *)0;
+    return NULL;
 
   old_size = *((unsigned *)ptr - EXTRA_SPACE_START + BLK_SIZE);
   cpy_size = (old_size > new_size) ? new_size : old_size;
@@ -243,11 +243,11 @@ dbg_strdup (const char *s, const char *pos)
   char *buf;
 
   if (s == NULL)
-    return (char *)0;
+    return NULL;
 
   size = strlen (s);
   if ((buf = dbg_malloc (size + 1, pos)) == NULL)
-    return (char *)0;
+    return NULL;
 
   return strncpy (buf, s, size + 1);
 }

src/notify.c

@@ -225,7 +225,7 @@ notify_launch_cmd (void)
   else if (pid == 0)
     {
       /* Child: launch user defined command */
-      if (execlp (nbar.shell, nbar.shell, "-c", nbar.cmd, (char *)0) < 0)
+      if (execlp (nbar.shell, nbar.shell, "-c", nbar.cmd, NULL) < 0)
         {
           ERROR_MSG (_("error while launching command"));
           _exit (1);
@@ -360,7 +360,7 @@ notify_main_thread (void *arg)
             notify_check_next_app (0);
         }
     }
-  pthread_exit ((void *) 0);
+  pthread_exit (NULL);
 }
 
 /* Fill the given structure with information about next appointment. */
@@ -377,7 +377,7 @@ notify_get_next (struct notify_app *a)
   a->time = current_time + DAYINSEC;
   a->got_app = 0;
   a->state = 0;
-  a->txt = (char *)0;
+  a->txt = NULL;
   recur_apoint_check_next (a, current_time, get_today ());
   apoint_check_next (a, current_time);
 
@@ -393,7 +393,7 @@ notify_get_next_bkgd (void)
 {
   struct notify_app a;
 
-  a.txt = (char *)0;
+  a.txt = NULL;
   if (!notify_get_next (&a))
     return 0;
 
@@ -422,7 +422,7 @@ notify_app_txt (void)
   if (notify_app.got_app)
     return notify_app.txt;
   else
-    return (char *)0;
+    return NULL;
 }
 
 /* Look for the next appointment within the next 24 hours. */
@@ -434,7 +434,7 @@ notify_thread_app (void *arg)
   int force = (arg ? 1 : 0);
 
   if (!notify_get_next (&tmp_app))
-    pthread_exit ((void *)0);
+    pthread_exit (NULL);
 
   if (!tmp_app.got_app)
     {
@@ -456,7 +456,7 @@ notify_thread_app (void *arg)
     mem_free (tmp_app.txt);
   notify_update_bar ();
 
-  pthread_exit ((void *) 0);
+  pthread_exit (NULL);
 }
 
 /* Launch the thread notify_thread_app to look for next appointment. */
@@ -464,7 +464,7 @@ void
 notify_check_next_app (int force)
 {
   pthread_t notify_t_app;
-  void *arg = (force ? (void *)1 : (void *)0);
+  void *arg = (force ? (void *)1 : NULL);
 
   pthread_create (&notify_t_app, &detached_thread_attr, notify_thread_app,
                   arg);

src/sigs.c

@@ -83,7 +83,7 @@ sigs_set_hdlr (int sig, void (*handler)(int))
   sigemptyset (&sa.sa_mask);
   sa.sa_handler = handler;
   sa.sa_flags = 0;
-  if (sigaction (sig, &sa, (struct sigaction *)0) == -1)
+  if (sigaction (sig, &sa, NULL) == -1)
     {
       ERROR_MSG (_("Error setting signal #%d : %s\n"),
                  sig, strerror (errno));

src/utils.c

@@ -419,7 +419,7 @@ item_in_popup (char *saved_a_start, char *saved_a_end, char *msg,
   const int padl = winl - 2, padw = winw - margin_left;
 
   pad = newpad (padl, padw);
-  popup_win = popup (winl, winw, 1, 2, pop_title, (char *)0, 1);
+  popup_win = popup (winl, winw, 1, 2, pop_title, NULL, 1);
   if (strncmp (pop_title, _("Appointment"), 11) == 0)
     {
       mvwprintw (popup_win, margin_top, margin_left, "- %s -> %s",
@@ -557,7 +557,7 @@ new_tempfile (const char *prefix, int trailing_len)
           close (fd);
         }
       ERROR_MSG (_("temporary file \"%s\" could not be created"), fullname);
-      return (char *)0;
+      return NULL;
     }
   fclose (file);