gdb: add filename option support

This commit adds support for filename options to GDB's option
sub-system (see cli/cli-option.{c,h}).

The new filename options support quoted and escaped filenames, and tab
completion is fully supported.

This commit adds the new option, and adds these options to the
'maintenance test-options' command as '-filename', along with some
tests that exercise this new option.

I've split the -filename testing into two.  In gdb.base/options.exp we
use the -filename option with some arbitrary strings.  This tests that
GDB can correctly extract the value from a filename option, and that
GDB can complete other options after a filename option.  However,
these tests don't actually pass real filenames, nor do they test
filename completion.

In gdb.base/filename-completion.exp I have added some tests that test
the -filename option with real filenames, and exercise filename tab
completion.

This commit doesn't include any real uses of the new filename options,
that will come in the next commit.

1 files changed, 20 insertions, 0 deletions

diff --git a/gdb/cli/cli-option.h b/gdb/cli/cli-option.h
index bbe281d..26307a5 100644
--- a/gdb/cli/cli-option.h
+++ b/gdb/cli/cli-option.h
@@ -308,6 +308,26 @@ struct string_option_def : option_def
   }
 };
 
+/* A var_filename command line option.  */
+
+template<typename Context>
+struct filename_option_def : option_def
+{
+  filename_option_def (const char *long_option_,
+		       std::string *(*get_var_address_cb_) (Context *),
+		       show_value_ftype *show_cmd_cb_,
+		       const char *set_doc_,
+		       const char *show_doc_ = nullptr,
+		       const char *help_doc_ = nullptr)
+    : option_def (long_option_, var_filename, nullptr,
+		  (erased_get_var_address_ftype *) get_var_address_cb_,
+		  show_cmd_cb_,
+		  set_doc_, show_doc_, help_doc_)
+  {
+    var_address.string = detail::get_var_address<std::string, Context>;
+  }
+};
+
 /* A group of options that all share the same context pointer to pass
    to the options' get-current-value callbacks.  */
 struct option_def_group