-Wwrite-strings: Some constification in gdb/breakpoint.c

The main motivation here is avoiding having to write a couple casts
like these:

     if (!arg)
  -    arg = "";
  +    arg = (char *) "";

in catch_exception_command_1 and catch_exec_command_1.

That requires making ep_parse_optional_if_clause and
check_for_argument take pointers to const strings.  I then tried
propagating the resulting constification all the way, but that was
spiraling out of control, so instead I settled for keeping const and
non-const overloads.

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

	* break-catch-throw.c (handle_gnu_v3_exceptions): Constify
	'cond_string' parameter.
	(extract_exception_regexp): Constify 'string' parameter.
	(catch_exception_command_1): Constify.
	* breakpoint.c (init_catchpoint)
	(create_fork_vfork_event_catchpoint): Constify 'cond_string'
	parameter.
	(ep_parse_optional_if_clause, catch_fork_command_1)
	(catch_exec_command_1): Constify.
	* breakpoint.h (init_catchpoint): Constify 'cond_string'
	parameter.
	(ep_parse_optional_if_clause): Constify.
	* cli/cli-utils.c (remove_trailing_whitespace)
	(check_for_argument): Constify.
	* cli/cli-utils.h (remove_trailing_whitespace): Constify and add
	non-const overload.
	(check_for_argument): Likewise.

1 files changed, 14 insertions, 12 deletions

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index f0db3e4..4cd7a00 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -8582,7 +8582,7 @@ catch_unload_command_1 (char *arg, int from_tty,
 void
 init_catchpoint (struct breakpoint *b,
 		 struct gdbarch *gdbarch, int tempflag,
-		 char *cond_string,
+		 const char *cond_string,
 		 const struct breakpoint_ops *ops)
 {
   struct symtab_and_line sal;
@@ -8613,7 +8613,7 @@ install_breakpoint (int internal, struct breakpoint *b, int update_gll)
 
 static void
 create_fork_vfork_event_catchpoint (struct gdbarch *gdbarch,
-				    int tempflag, char *cond_string,
+				    int tempflag, const char *cond_string,
                                     const struct breakpoint_ops *ops)
 {
   struct fork_catchpoint *c = new fork_catchpoint ();
@@ -11779,10 +11779,10 @@ until_break_command (char *arg, int from_tty, int anywhere)
    it updates arg to point to the first character following the parsed
    if clause in the arg string.  */
 
-char *
-ep_parse_optional_if_clause (char **arg)
+const char *
+ep_parse_optional_if_clause (const char **arg)
 {
-  char *cond_string;
+  const char *cond_string;
 
   if (((*arg)[0] != 'i') || ((*arg)[1] != 'f') || !isspace ((*arg)[2]))
     return NULL;
@@ -11792,7 +11792,7 @@ ep_parse_optional_if_clause (char **arg)
 
   /* Skip any extra leading whitespace, and record the start of the
      condition string.  */
-  *arg = skip_spaces (*arg);
+  *arg = skip_spaces_const (*arg);
   cond_string = *arg;
 
   /* Assume that the condition occupies the remainder of the arg
@@ -11813,11 +11813,12 @@ typedef enum
 catch_fork_kind;
 
 static void
-catch_fork_command_1 (char *arg, int from_tty, 
+catch_fork_command_1 (char *arg_entry, int from_tty,
 		      struct cmd_list_element *command)
 {
+  const char *arg = arg_entry;
   struct gdbarch *gdbarch = get_current_arch ();
-  char *cond_string = NULL;
+  const char *cond_string = NULL;
   catch_fork_kind fork_kind;
   int tempflag;
 
@@ -11827,7 +11828,7 @@ catch_fork_command_1 (char *arg, int from_tty,
 
   if (!arg)
     arg = "";
-  arg = skip_spaces (arg);
+  arg = skip_spaces_const (arg);
 
   /* The allowed syntax is:
      catch [v]fork
@@ -11860,19 +11861,20 @@ catch_fork_command_1 (char *arg, int from_tty,
 }
 
 static void
-catch_exec_command_1 (char *arg, int from_tty, 
+catch_exec_command_1 (char *arg_entry, int from_tty,
 		      struct cmd_list_element *command)
 {
+  const char *arg = arg_entry;
   struct exec_catchpoint *c;
   struct gdbarch *gdbarch = get_current_arch ();
   int tempflag;
-  char *cond_string = NULL;
+  const char *cond_string = NULL;
 
   tempflag = get_cmd_context (command) == CATCH_TEMPORARY;
 
   if (!arg)
     arg = "";
-  arg = skip_spaces (arg);
+  arg = skip_spaces_const (arg);
 
   /* The allowed syntax is:
      catch exec