Declare several parameters/variables constant

Add the "const" keyword to parameters and variables that are never
modified. Most of these were spotted by "-Wwrite-strings".

We cast the second parameter to execvp() explicitly as it expects a
"char *const[]" where it should expect a "const char *const[]"
(according to the documentation, this is due to compatibility reasons).
This should be changed once we come up with a better solution.

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

17 files changed, 125 insertions, 122 deletions

diff --git a/src/args.c b/src/args.c
index b861018..1a4b38c 100644
--- a/src/args.c
+++ b/src/args.c
@@ -480,8 +480,9 @@ display_app (struct tm *t, int numdays, int add_line, const char *fmt_apt,
  * days.
  */
 static void
-date_arg (char *ddate, int add_line, const char *fmt_apt, const char *fmt_rapt,
-          const char *fmt_ev, const char *fmt_rev, regex_t *regex)
+date_arg (const char *ddate, int add_line, const char *fmt_apt,
+          const char *fmt_rapt, const char *fmt_ev, const char *fmt_rev,
+          regex_t *regex)
 {
   int i;
   struct date day;
@@ -544,7 +545,7 @@ date_arg (char *ddate, int add_line, const char *fmt_apt, const char *fmt_rapt,
  * Many thanks to Erik Saule for providing this function.
  */
 static void
-date_arg_extended (char *startday, char *range, int add_line,
+date_arg_extended (const char *startday, const char *range, int add_line,
                    const char *fmt_apt, const char *fmt_rapt,
                    const char *fmt_ev, const char *fmt_rev, regex_t *regex)
 {
@@ -633,8 +634,8 @@ parse_args (int argc, char **argv)
   const char *fmt_todo = "%p. %m\n";
 
   int tnum = 0, xfmt = 0, non_interactive = 0, multiple_flag = 0, load_data = 0;
-  char *ddate = "", *cfile = NULL, *range = NULL, *startday = NULL;
-  char *datadir = NULL, *ifile = NULL;
+  const char *ddate = "", *cfile = NULL, *range = NULL, *startday = NULL;
+  const char *datadir = NULL, *ifile = NULL;
   regex_t reg, *preg = NULL;
 
   /* Long options only */
@@ -644,7 +645,7 @@ parse_args (int argc, char **argv)
     STATUS_OPT = CHAR_MAX + 1
   };
 
-  static char *optstr = "ghvnNax::t::d:c:r::s::S:D:i:";
+  static const char *optstr = "ghvnNax::t::d:c:r::s::S:D:i:";
 
   struct option longopts[] = {
     {"appointment", no_argument, NULL, 'a'},
diff --git a/src/calcurse.h b/src/calcurse.h
index b07ce45..f2e6991 100644
--- a/src/calcurse.h
+++ b/src/calcurse.h
@@ -228,17 +228,17 @@
 
 /* General configuration variables. */
 struct conf {
-  unsigned   auto_save;
-  unsigned   auto_gc;
-  unsigned   periodic_save;
-  unsigned   confirm_quit;
-  unsigned   confirm_delete;
-  unsigned   system_dialogs;
-  unsigned   progress_bar;
-  char      *editor;
-  char      *pager;
-  char       output_datefmt[BUFSIZ];  /* format for displaying date */
-  int        input_datefmt;           /* format for reading date */
+  unsigned    auto_save;
+  unsigned    auto_gc;
+  unsigned    periodic_save;
+  unsigned    confirm_quit;
+  unsigned    confirm_delete;
+  unsigned    system_dialogs;
+  unsigned    progress_bar;
+  const char *editor;
+  const char *pager;
+  char        output_datefmt[BUFSIZ];  /* format for displaying date */
+  int         input_datefmt;           /* format for reading date */
 };
 
 /* Daemon-related configuration. */
@@ -482,7 +482,7 @@ struct nbar {
   char             datefmt[BUFSIZ];  /* format for displaying date */
   char             timefmt[BUFSIZ];  /* format for displaying time */
   char             cmd[BUFSIZ];      /* notification command */
-  char            *shell;            /* user shell to launch notif. cmd */
+  const char      *shell;            /* user shell to launch notif. cmd */
   unsigned         notify_all;       /* notify all appointments */
   pthread_mutex_t  mutex;
 };
@@ -618,7 +618,7 @@ void          calendar_change_day (int);
 void          calendar_move (enum move, int);
 long          calendar_start_of_year (void);
 long          calendar_end_of_year (void);
-char         *calendar_get_pom (time_t);
+const char   *calendar_get_pom (time_t);
 
 /* config.c */
 
@@ -654,8 +654,8 @@ int                   day_cut_item (long, int);
 int                   day_paste_item (long, int);
 struct day_item      *day_get_item (int);
 int                   day_item_nb (long, int, int);
-void                  day_edit_note (char *);
-void                  day_view_note (char *);
+void                  day_edit_note (const char *);
+void                  day_view_note (const char *);
 void                  day_pipe_item (void);
 
 /* dmon.c */
@@ -690,7 +690,7 @@ void  ical_export_data (FILE *);
 
 /* io.c */
 unsigned         io_fprintln (const char *, const char *, ...);
-void             io_init (char *, char *);
+void             io_init (const char *, const char *);
 void             io_extract_data (char *, const char *, int);
 unsigned         io_save_apts (void);
 unsigned         io_save_todo (void);
@@ -698,7 +698,7 @@ unsigned         io_save_keys (void);
 void             io_save_cal (enum save_display);
 void             io_load_app (void);
 void             io_load_todo (void);
-void             io_load_keys (char *);
+void             io_load_keys (const char *);
 void             io_check_dir (char *, int *);
 unsigned         io_file_exist (char *);
 void             io_check_file (char *, int *);
@@ -706,10 +706,10 @@ int              io_check_data_files (void);
 void             io_startup_screen (int);
 void             io_export_data (enum export_type);
 void             io_export_bar (void);
-void             io_import_data (enum import_type, char *);
+void             io_import_data (enum import_type, const char *);
 struct io_file  *io_log_init (void);
 void             io_log_print (struct io_file *, int, const char *);
-void             io_log_display (struct io_file *, const char *, char *);
+void             io_log_display (struct io_file *, const char *, const char *);
 void             io_log_free (struct io_file *);
 void             io_start_psave_thread (void);
 void             io_stop_psave_thread (void);
@@ -720,26 +720,26 @@ int              io_file_is_empty (char *);
 int              io_file_cp (const char *, const char *);
 
 /* keys.c */
-void      keys_init (void);
-void      keys_free (void);
-void      keys_dump_defaults (char *);
-char     *keys_get_label (enum key);
-enum key  keys_get_action (int);
-enum key  keys_getch (WINDOW *win, int *);
-int       keys_assign_binding (int, enum key);
-void      keys_remove_binding (int, enum key);
-int       keys_str2int (char *);
-char     *keys_int2str (int);
-int       keys_action_count_keys (enum key);
-char     *keys_action_firstkey (enum key);
-char     *keys_action_nkey (enum key, int);
-char     *keys_action_allkeys (enum key);
-void      keys_display_bindings_bar (WINDOW *, struct binding *[], int, int,
-                                     int, struct binding *);
-void      keys_popup_info (enum key);
-void      keys_save_bindings (FILE *);
-int       keys_check_missing_bindings (void);
-void      keys_fill_missing (void);
+void        keys_init (void);
+void        keys_free (void);
+void        keys_dump_defaults (char *);
+const char *keys_get_label (enum key);
+enum key    keys_get_action (int);
+enum key    keys_getch (WINDOW *win, int *);
+int         keys_assign_binding (int, enum key);
+void        keys_remove_binding (int, enum key);
+int         keys_str2int (const char *);
+const char *keys_int2str (int);
+int         keys_action_count_keys (enum key);
+const char *keys_action_firstkey (enum key);
+const char *keys_action_nkey (enum key, int);
+char       *keys_action_allkeys (enum key);
+void        keys_display_bindings_bar (WINDOW *, struct binding *[], int, int,
+                                       int, struct binding *);
+void        keys_popup_info (enum key);
+void        keys_save_bindings (FILE *);
+int         keys_check_missing_bindings (void);
+void        keys_fill_missing (void);
 
 /* mem.c */
 void  *xmalloc (size_t);
@@ -776,8 +776,8 @@ void   mem_stats (void);
 
 /* note.c */
 char *generate_note (const char *);
-void  edit_note (char **, char *);
-void  view_note (char *, char *);
+void  edit_note (char **, const char *);
+void  view_note (const char *, const char *);
 void  erase_note (char **);
 void  note_read (char *, FILE *);
 void  note_gc (void);
@@ -879,8 +879,8 @@ void          todo_delete (void);
 void          todo_chg_priority (int);
 void          todo_edit_item (void);
 void          todo_update_panel (int);
-void          todo_edit_note (char *);
-void          todo_view_note (char *);
+void          todo_edit_note (const char *);
+void          todo_view_note (const char *);
 void          todo_pipe_item (void);
 void          todo_init_list (void);
 void          todo_free_list (void);
@@ -897,21 +897,22 @@ void         warnbox (const char *);
 void         status_mesg (const char *, const char *);
 void         status_mesg_yesno (const char *);
 void         erase_window_part (WINDOW *, int, int, int, int);
-WINDOW      *popup (int, int, int, int, char *, char *, int);
+WINDOW      *popup (int, int, int, int, const char *, const char *, int);
 void         print_in_middle (WINDOW *, int, int, int, const char *);
 int          is_all_digit (const char *);
 long         get_item_time (long);
 int          get_item_hour (long);
 int          get_item_min (long);
 long         date2sec (struct date, unsigned, unsigned);
-char        *date_sec2date_str (long, char *);
+char        *date_sec2date_str (long, const char *);
 void         date_sec2date_fmt (long, const char *, char *);
 long         date_sec_change (long, int, int);
 long         update_time_in_date (long, unsigned, unsigned);
 long         get_sec_date (struct date);
 long         min2sec (unsigned);
 void         draw_scrollbar (WINDOW *, int, int, int, int, int, unsigned);
-void         item_in_popup (char *, char *, char *, char *);
+void         item_in_popup (const char *, const char *, const char *,
+                            const char *);
 long         get_today (void);
 long         now (void);
 char        *nowstr (void);
@@ -926,8 +927,8 @@ int          parse_duration (const char *, unsigned *);
 void         str_toupper (char *);
 void         file_close (FILE *, const char *);
 void         psleep (unsigned);
-int          fork_exec (int *, int *, const char *, char *const *);
-int          shell_exec (int *, int *, char *);
+int          fork_exec (int *, int *, const char *, const char *const *);
+int          shell_exec (int *, int *, const char *);
 int          child_wait (int *, int *, int);
 void         press_any_key (void);
 void         print_apoint (const char *, long, struct apoint *);
@@ -945,8 +946,8 @@ extern int               foreground, background;
 extern enum ui_mode      ui_mode;
 extern int               read_only;
 extern int               days[12];
-extern char             *monthnames[12];
-extern char             *daynames[8];
+extern const char       *monthnames[12];
+extern const char       *daynames[8];
 extern char              path_dir[BUFSIZ];
 extern char              path_todo[BUFSIZ];
 extern char              path_apts[BUFSIZ];
@@ -994,7 +995,7 @@ void      wins_update (int);
 void      wins_reset (void);
 void      wins_prepare_external (void);
 void      wins_unprepare_external (void);
-void      wins_launch_external (char *, char *);
+void      wins_launch_external (const char *, const char *);
 void      wins_status_bar (void);
 void      wins_erase_status_bar (void);
 void      wins_other_status_page (int);
diff --git a/src/calendar.c b/src/calendar.c
index 7ef7f0f..564ee70 100644
--- a/src/calendar.c
+++ b/src/calendar.c
@@ -632,7 +632,7 @@ calendar_change_day (int datefmt)
     _("The day you entered is not valid "
       "(should be between 01/01/1902 and 12/31/2037)");
   const char *mesg_line2 = _("Press [ENTER] to continue");
-  char *request_date = "Enter the day to go to [ENTER for today] : %s";
+  const char *request_date = "Enter the day to go to [ENTER for today] : %s";
 
   while (wrong_day)
     {
@@ -910,10 +910,10 @@ pom (time_t tmpt)
  * Careful: date is the selected day in calendar at 00:00, so it represents
  * the phase of the moon for previous day.
  */
-char *
+const char *
 calendar_get_pom (time_t date)
 {
-  char *pom_pict[MOON_PHASES] = { "   ", "|) ", "(|)", "(| ", " | " };
+  const char *pom_pict[MOON_PHASES] = { "   ", "|) ", "(|)", "(| ", " | " };
   enum pom phase = NO_POM;
   double pom_today, relative_pom, pom_yesterday, pom_tomorrow;
   const double half = 50.0;
diff --git a/src/config.c b/src/config.c
index 30c98e1..88d5acc 100644
--- a/src/config.c
+++ b/src/config.c
@@ -337,9 +337,9 @@ config_color_theme_name (char *theme_name)
 
   int i;
   short color[NBCOLORS];
-  char *color_name[NBCOLORS];
-  char *default_color = "default";
-  char *name[MAXCOLORS] = {
+  const char *color_name[NBCOLORS];
+  const char *default_color = "default";
+  const char *name[MAXCOLORS] = {
     "black",
     "red",
     "green",
diff --git a/src/custom.c b/src/custom.c
index e347850..960837d 100644
--- a/src/custom.c
+++ b/src/custom.c
@@ -157,7 +157,7 @@ display_layout_config (struct window *lwin, int mark, int cursor)
 #define MARK			88
 #define LAYOUTH                  5
 #define LAYOUTW                  9
-  char *box = "[ ]";
+  const char *box = "[ ]";
   const int BOXSIZ = strlen (box);
   const int NBCOLS = NBLAYOUTS / LAYOUTSPERCOL;
   const int COLSIZ = LAYOUTW + BOXSIZ + 1;
@@ -167,7 +167,7 @@ display_layout_config (struct window *lwin, int mark, int cursor)
   const int YOFST = (lwin->h - LAYOUTSPERCOL * (YSPC + LAYOUTH)) / 2;
   enum {YPOS, XPOS, NBPOS};
   int pos[NBLAYOUTS][NBPOS];
-  char *layouts[LAYOUTH][NBLAYOUTS] = {
+  const char *layouts[LAYOUTH][NBLAYOUTS] = {
     {"+---+---+", "+---+---+", "+---+---+", "+---+---+", "+---+---+", "+---+---+", "+---+---+", "+---+---+"},
     {"|   | c |", "|   | t |", "| c |   |", "| t |   |", "|   | c |", "|   | a |", "| c |   |", "| a |   |"},
     {"| a +---+", "| a +---+", "+---+ a |", "|---+ a |", "| t +---+", "| t +---+", "+---+ t |", "+---+ t |"},
@@ -434,8 +434,8 @@ display_color_config (struct window *cwin, int *mark_fore, int *mark_back,
   const char *fore_txt = _("Foreground");
   const char *back_txt = _("Background");
   const char *default_txt = _("(terminal's default)");
-  char *bar = "          ";
-  char *box = "[ ]";
+  const char *bar = "          ";
+  const char *box = "[ ]";
   const unsigned Y = 3;
   const unsigned XOFST = 5;
   const unsigned YSPC = (cwin->h - 8) / (NBUSERCOLORS + 1);
@@ -869,7 +869,7 @@ custom_general_config (void)
 
 
 static void
-print_key_incolor (WINDOW *win, char *option, int pos_y, int pos_x)
+print_key_incolor (WINDOW *win, const char *option, int pos_y, int pos_x)
 {
   const int color = ATTR_HIGHEST;
 
@@ -907,7 +907,7 @@ print_keys_bindings (WINDOW *win, int selected_row, int selected_elm, int yoff)
         {
           if (action == selected_row)
             {
-              char *key;
+              const char *key;
               int pos;
 
               pos = KEYPOS;
@@ -959,7 +959,7 @@ custom_keys_config (void)
   struct scrollwin kwin;
   int selrow, selelm, firstrow, lastrow, nbrowelm, nbdisplayed;
   int keyval, used, not_recognized;
-  char *keystr;
+  const char *keystr;
   WINDOW *grabwin;
   const int LINESPERKEY = 2;
   const int LABELLINES = 3;
diff --git a/src/day.c b/src/day.c
index 2660fee..8ed5de7 100644
--- a/src/day.c
+++ b/src/day.c
@@ -705,7 +705,7 @@ update_rept (struct rpt **rpt, const long start)
   const char *msg_wrong_freq = _("The frequence you entered is not valid.");
   const char *msg_wrong_time = _("Invalid time: start time must be before end time!");
   const char *msg_wrong_date = _("The entered date is not valid.");
-  char *msg_fmts =
+  const char *msg_fmts =
     "Possible formats are [%s] or '0' for an endless repetetition";
   const char *msg_enter = _("Press [Enter] to continue");
 
@@ -1092,7 +1092,7 @@ day_item_nb (long date, int day_num, int type)
 
 /* Attach a note to an appointment or event. */
 void
-day_edit_note (char *editor)
+day_edit_note (const char *editor)
 {
   struct day_item *p;
   struct recur_apoint *ra;
@@ -1130,7 +1130,7 @@ day_edit_note (char *editor)
 
 /* View a note previously attached to an appointment or event */
 void
-day_view_note (char *pager)
+day_view_note (const char *pager)
 {
   struct day_item *p = day_get_item (apoint_hilt ());
   view_note (p->note, pager);
diff --git a/src/help.c b/src/help.c
index 3c3ebbf..04c25d9 100644
--- a/src/help.c
+++ b/src/help.c
@@ -100,7 +100,7 @@ static int
 help_write_pad (struct window *win, char *title, char *text, enum key action)
 {
   int colnum, rownum;
-  char *bindings_title = "key bindings: %s";
+  const char *bindings_title = "key bindings: %s";
   char *bindings;
 
   colnum = 0;
diff --git a/src/htable.h b/src/htable.h
index 654bf57..91d01d8 100644
--- a/src/htable.h
+++ b/src/htable.h
@@ -118,7 +118,7 @@ uint32_t                                                                      \
 name##_HTABLE_FIND_BKT(struct name *head, struct type *elm)                   \
 {                                                                             \
   uint32_t __bkt;                                                             \
-  char *__key;                                                                \
+  const char *__key;                                                                \
   int __len;                                                                  \
                                                                               \
   (key) (elm, &__key, &__len);                                                \
diff --git a/src/ical.c b/src/ical.c
index d646072..375f3a1 100644
--- a/src/ical.c
+++ b/src/ical.c
@@ -68,7 +68,7 @@ static void ical_export_apoints (FILE *);
 static void ical_export_todo (FILE *);
 static void ical_export_footer (FILE *);
 
-static char *ical_recur_type[RECUR_TYPES] =
+static const char *ical_recur_type[RECUR_TYPES] =
   { "", "DAILY", "WEEKLY", "MONTHLY", "YEARLY" };
 
 /* iCal alarm notification. */
diff --git a/src/io.c b/src/io.c
index f6388df..737a198 100644
--- a/src/io.c
+++ b/src/io.c
@@ -67,12 +67,13 @@ enum {
 };
 
 struct ht_keybindings_s {
-  char     *label;
-  enum key  key;
+  const char *label;
+  enum key    key;
   HTABLE_ENTRY (ht_keybindings_s);
 };
 
-static void load_keys_ht_getkey (struct ht_keybindings_s *, char **, int *);
+static void load_keys_ht_getkey (struct ht_keybindings_s *, const char **,
+                                 int *);
 static int load_keys_ht_compare (struct ht_keybindings_s *,
                                  struct ht_keybindings_s *);
 
@@ -94,14 +95,14 @@ progress_bar (progress_bar_t type, int progress)
   const char *mesg_load = _("Loading...");
   const char *mesg_export = _("Exporting...");
   const char *error_msg = _("Internal error while displaying progress bar");
-  char *barchar = "|";
-  char *file[NBFILES] = {
+  const char *barchar = "|";
+  const char *file[NBFILES] = {
     "[    conf    ]",
     "[    todo    ]",
     "[    apts    ]",
     "[    keys    ]"
   };
-  char *data[NBEXPORTED] = {
+  const char *data[NBEXPORTED] = {
     "[   events   ]",
     "[appointments]",
     "[    todo    ]"
@@ -226,10 +227,10 @@ io_fprintln (const char *fname, const char *fmt, ...)
  * The datadir argument can be use to specify an alternative data root dir.
  */
 void
-io_init (char *cfile, char *datadir)
+io_init (const char *cfile, const char *datadir)
 {
   FILE *data_file;
-  char *home;
+  const char *home;
   char apts_file[BUFSIZ] = "";
   int ch;
 
@@ -723,7 +724,7 @@ io_load_todo (void)
 }
 
 static void
-load_keys_ht_getkey (struct ht_keybindings_s *data, char **key, int *len)
+load_keys_ht_getkey (struct ht_keybindings_s *data, const char **key, int *len)
 {
   *key = data->label;
   *len = strlen (data->label);
@@ -760,7 +761,7 @@ static int is_blank (int c)
  * configuration file.
  */
 void
-io_load_keys (char *pager)
+io_load_keys (const char *pager)
 {
   struct ht_keybindings_s keys[NBKEYS];
   FILE *keyfp;
@@ -1108,7 +1109,7 @@ get_import_stream (enum export_type type)
  * and is cleared at the end.
  */
 void
-io_import_data (enum import_type type, char *stream_name)
+io_import_data (enum import_type type, const char *stream_name)
 {
   const char *proc_report = _("Import process report: %04d lines read ");
   char stats_str[4][BUFSIZ];
@@ -1232,7 +1233,7 @@ io_log_print (struct io_file *log, int line, const char *msg)
 }
 
 void
-io_log_display (struct io_file *log, const char *msg, char *pager)
+io_log_display (struct io_file *log, const char *msg, const char *pager)
 {
   int ans;
 
@@ -1243,7 +1244,7 @@ io_log_display (struct io_file *log, const char *msg, char *pager)
       ans = fgetc (stdin);
       if (ans == 'y')
         {
-          char *arg[] = { pager, log->name, NULL };
+          const char *arg[] = { pager, log->name, NULL };
           int pid;
 
           if ((pid = fork_exec (NULL, NULL, pager, arg)))
diff --git a/src/keys.c b/src/keys.c
index a218d6e..8647e67 100644
--- a/src/keys.c
+++ b/src/keys.c
@@ -42,8 +42,8 @@
 #define MAXKEYVAL   KEY_MAX  /* ncurses defines KEY_MAX as maximum key value */
 
 struct keydef_s {
-  char *label;
-  char *binding;
+  const char *label;
+  const char *binding;
 };
 
 static llist_t keys[NBKEYS];
@@ -166,7 +166,7 @@ keys_dump_defaults (char *file)
   file_close (fd, __FILE_POS__);
 }
 
-char *
+const char *
 keys_get_label (enum key key)
 {
   EXIT_IF (key < 0 || key > NBKEYS,
@@ -269,7 +269,7 @@ keys_remove_binding (int key, enum key action)
 }
 
 int
-keys_str2int (char *key)
+keys_str2int (const char *key)
 {
   const char CONTROL_KEY[] = "C-";
   const char TAB_KEY[] = "TAB";
@@ -315,7 +315,7 @@ keys_str2int (char *key)
     }
 }
 
-char *
+const char *
 keys_int2str (int key)
 {
   switch (key)
@@ -355,14 +355,14 @@ keys_action_count_keys (enum key action)
   return n;
 }
 
-char *
+const char *
 keys_action_firstkey (enum key action)
 {
-  char *s = LLIST_GET_DATA (LLIST_FIRST (&keys[action]));
+  const char *s = LLIST_GET_DATA (LLIST_FIRST (&keys[action]));
   return (s != NULL) ? s : "XXX";
 }
 
-char *
+const char *
 keys_action_nkey (enum key action, int keynum)
 {
   return LLIST_GET_DATA (LLIST_NTH (&keys[action], keynum));
diff --git a/src/note.c b/src/note.c
index a65a384..09b6d0d 100644
--- a/src/note.c
+++ b/src/note.c
@@ -46,7 +46,7 @@ struct note_gc_hash {
   HTABLE_ENTRY (note_gc_hash);
 };
 
-static void note_gc_extract_key (struct note_gc_hash *, char **, int *);
+static void note_gc_extract_key (struct note_gc_hash *, const char **, int *);
 static int note_gc_cmp (struct note_gc_hash *, struct note_gc_hash *);
 
 HTABLE_HEAD (htp, NOTE_GC_HSIZE, note_gc_hash);
@@ -74,7 +74,7 @@ generate_note (const char *str)
 
 /* Edit a note with an external editor. */
 void
-edit_note (char **note, char *editor)
+edit_note (char **note, const char *editor)
 {
   char tmppath[BUFSIZ];
   char *tmpext;
@@ -114,7 +114,7 @@ edit_note (char **note, char *editor)
 
 /* View a note in an external pager. */
 void
-view_note (char *note, char *pager)
+view_note (const char *note, const char *pager)
 {
   char fullname[BUFSIZ];
 
@@ -155,7 +155,7 @@ note_read (char *buffer, FILE *fp)
 }
 
 static void
-note_gc_extract_key (struct note_gc_hash *data, char **key, int *len)
+note_gc_extract_key (struct note_gc_hash *data, const char **key, int *len)
 {
   *key = data->hash;
   *len = strlen (data->hash);
diff --git a/src/notify.c b/src/notify.c
index 70b5419..0ef4189 100644
--- a/src/notify.c
+++ b/src/notify.c
@@ -119,9 +119,9 @@ notify_bar (void)
 void
 notify_init_vars (void)
 {
-  char *time_format = "%T";
-  char *date_format = "%a %F";
-  char *cmd = "printf '\\a'";
+  const char *time_format = "%T";
+  const char *date_format = "%a %F";
+  const char *cmd = "printf '\\a'";
 
   pthread_mutex_init (&nbar.mutex, NULL);
   nbar.show = 1;
diff --git a/src/todo.c b/src/todo.c
index 27e9c36..a4c75da 100644
--- a/src/todo.c
+++ b/src/todo.c
@@ -463,7 +463,7 @@ todo_update_panel (int which_pan)
 
 /* Attach a note to a todo */
 void
-todo_edit_note (char *editor)
+todo_edit_note (const char *editor)
 {
   struct todo *i = todo_get_item (hilt);
   edit_note (&i->note, editor);
@@ -471,7 +471,7 @@ todo_edit_note (char *editor)
 
 /* View a note previously attached to a todo */
 void
-todo_view_note (char *pager)
+todo_view_note (const char *pager)
 {
   struct todo *i = todo_get_item (hilt);
   view_note (i->note, pager);
diff --git a/src/utils.c b/src/utils.c
index aa4a2d6..8ddbe59 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -148,7 +148,7 @@ void
 warnbox (const char *msg)
 {
   WINDOW *warnwin;
-  char *label = "/!\\";
+  const char *label = "/!\\";
   const int WINROW = 10;
   const int WINCOL = col - 2;
   const int MSGLEN = WINCOL - 2;
@@ -207,8 +207,8 @@ erase_window_part (WINDOW *win, int first_col, int first_row, int last_col,
 
 /* draws a popup window */
 WINDOW *
-popup (int pop_row, int pop_col, int pop_y, int pop_x, char *title, char *msg,
-       int hint)
+popup (int pop_row, int pop_col, int pop_y, int pop_x, const char *title,
+       const char *msg, int hint)
 {
   const char *any_key = _("Press any key to continue...");
   char label[BUFSIZ];
@@ -308,7 +308,7 @@ date2sec (struct date day, unsigned hour, unsigned min)
 
 /* Return a string containing the date, given a date in seconds. */
 char *
-date_sec2date_str (long sec, char *datefmt)
+date_sec2date_str (long sec, const char *datefmt)
 {
   struct tm *lt;
   char *datestr = (char *) mem_calloc (BUFSIZ, sizeof (char));
@@ -431,8 +431,8 @@ draw_scrollbar (WINDOW *win, int y, int x, int length,
  * long to fit in its corresponding panel window.
  */
 void
-item_in_popup (char *saved_a_start, char *saved_a_end, char *msg,
-               char *pop_title)
+item_in_popup (const char *saved_a_start, const char *saved_a_end,
+               const char *msg, const char *pop_title)
 {
   WINDOW *popup_win, *pad;
   const int margin_left = 4, margin_top = 4;
@@ -866,7 +866,7 @@ psleep (unsigned secs)
  * appropriate file descriptors are written to pfdin/pfdout.
  */
 int
-fork_exec (int *pfdin, int *pfdout, const char *path, char *const *arg)
+fork_exec (int *pfdin, int *pfdout, const char *path, const char *const *arg)
 {
   int pin[2], pout[2];
   int pid;
@@ -894,7 +894,7 @@ fork_exec (int *pfdin, int *pfdout, const char *path, char *const *arg)
           close (pin[1]);
         }
 
-      execvp (path, arg);
+      execvp (path, (char *const *)arg);
       _exit (127);
     }
   else
@@ -931,9 +931,9 @@ fork_exec (int *pfdin, int *pfdout, const char *path, char *const *arg)
 
 /* Execute an external program in a shell. */
 int
-shell_exec (int *pfdin, int *pfdout, char *cmd)
+shell_exec (int *pfdin, int *pfdout, const char *cmd)
 {
-  char *arg[] = { "/bin/sh", "-c", cmd, NULL };
+  const char *arg[] = { "/bin/sh", "-c", cmd, NULL };
   return fork_exec (pfdin, pfdout, *arg, arg);
 }
 
@@ -973,7 +973,7 @@ press_any_key (void)
  * (patch submitted by Erik Saule).
  */
 static void
-print_notefile (FILE *out, char *filename, int nbtab)
+print_notefile (FILE *out, const char *filename, int nbtab)
 {
   char path_to_notefile[BUFSIZ];
   FILE *notefile;
diff --git a/src/vars.c b/src/vars.c
index 056cb71..db8541b 100644
--- a/src/vars.c
+++ b/src/vars.c
@@ -65,7 +65,7 @@ int read_only = 0;
  * variables to store calendar names
  */
 int days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
-char *monthnames[12] = {
+const char *monthnames[12] = {
   N_("January"),
   N_("February"),
   N_("March"),
@@ -80,7 +80,7 @@ char *monthnames[12] = {
   N_("December")
 };
 
-char *daynames[8] = {
+const char *daynames[8] = {
   N_("Sun"),
   N_("Mon"),
   N_("Tue"),
@@ -123,7 +123,7 @@ struct dmon_conf dmon;
 void
 vars_init (void)
 {
-  char *ed, *pg;
+  const char *ed, *pg;
 
   /* Variables for user configuration */
   conf.confirm_quit = 1;
diff --git a/src/wins.c b/src/wins.c
index a1004d2..cdb6f5b 100644
--- a/src/wins.c
+++ b/src/wins.c
@@ -620,9 +620,9 @@ wins_unprepare_external (void)
  * file.
  */
 void
-wins_launch_external (char *file, char *cmd)
+wins_launch_external (const char *file, const char *cmd)
 {
-  char *arg[] = { cmd, file, NULL };
+  const char *arg[] = { cmd, file, NULL };
   int pid;
 
   wins_prepare_external ();