-Wwrite-strings: Constify word break character arrays

-Wwrite-strings flags several cases of missing casts around
initializations like:

   static char *gdb_completer_command_word_break_characters =
    " \t\n!@#$%^&*()+=|~`}{[]\"';:?/>.<,";

Obviously these could/should be const.  However, while at it, there's
no need for these variables to be pointers instead of arrays.  They
are never changed to point to anything else.

Unfortunately, readline's rl_completer_word_break_characters is
"char *", not "const char *".  So we always need a cast somewhere.  The
approach taken here is to add a new
set_rl_completer_word_break_characters function that becomes the only
place that writes to rl_completer_word_break_characters, and thus the
single place that needs the cast.

gdb/ChangeLog:
2017-04-05  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_completer_word_break_characters): Now a const
	array.
	(ada_get_gdb_completer_word_break_characters): Constify.
	* completer.c (gdb_completer_command_word_break_characters)
	(gdb_completer_file_name_break_characters)
	(gdb_completer_quote_characters): Now const arrays.
	(get_gdb_completer_quote_characters): Constify.
	(set_rl_completer_word_break_characters): New function.
	(set_gdb_completion_word_break_characters)
	(complete_line_internal): Use it.
	* completer.h (get_gdb_completer_quote_characters): Constify.
	(set_rl_completer_word_break_characters): Declare.
	* f-lang.c (f_word_break_characters): Constify.
	* language.c (default_word_break_characters): Constify.
	* language.h (language_defn::la_word_break_characters): Constify.
	(default_word_break_characters): Constify.
	* top.c (init_main): Use set_rl_completer_word_break_characters.

1 files changed, 7 insertions, 1 deletions

diff --git a/gdb/completer.h b/gdb/completer.h
index 416b3134f5..2aa1987f30 100644
--- a/gdb/completer.h
+++ b/gdb/completer.h
@@ -99,10 +99,16 @@ extern VEC (char_ptr) *reg_or_group_completer (struct cmd_list_element *,
 extern VEC (char_ptr) *reggroup_completer (struct cmd_list_element *,
 					   const char *, const char *);
 
-extern char *get_gdb_completer_quote_characters (void);
+extern const char *get_gdb_completer_quote_characters (void);
 
 extern char *gdb_completion_word_break_characters (void);
 
+/* Set the word break characters array to BREAK_CHARS.  This function
+   is useful as const-correct alternative to direct assignment to
+   rl_completer_word_break_characters, which is "char *",
+   not "const char *".  */
+extern void set_rl_completer_word_break_characters (const char *break_chars);
+
 /* Set the word break characters array to the corresponding set of
    chars, based on FN.  This function is useful for cases when the
    completer doesn't know the type of the completion until some