[PATCH 1/2] gdb: Allow target description to be dumped even when it is remote

[Andrew Burgess <andrew.burgess@embecosm.com>]

The maintenance command 'maintenance print c-tdesc' can only print the
target description if it was loaded from a local file, or if the local
filename is passed to the maintenance command as an argument.

Sometimes it would be nice to know what target description GDB was
given by the remote, however, if I connect to a remote target and try
this command I see this:

  (gdb) maintenance print c-tdesc
  The current target description did not come from an XML file.
  (gdb)

Which is not very helpful.

This commit changes things so that if the description came from the
remote end then GDB will use the fake filename 'target.xml' as the
filename for the description, GDB will then create the C description
of the target as if it was in a file 'target.xml'.

I originally added this functionality so I could inspect the
description passed to GDB by the remote target.  After using this for
a while I realised that actually having GDB recreate the XML would be
even better, so a later commit will add that functionality too.

Still, given how small this patch is I thought it might be nice to
include this in GDB anyway.

While I was working on this anyway I've added filename command
completion to this command.

gdb/ChangeLog:

	* target-descriptions.c (maint_print_c_tdesc_cmd): Use fake
	filename for target descriptions that came from the target.
	(_initialize_target_descriptions): Add filename command completion
	for 'maint print c-tdesc'.
---
 gdb/ChangeLog             |  7 +++++++
 gdb/target-descriptions.c | 14 ++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index 20a3a640f4f..55ea416d69a 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -1680,7 +1680,12 @@ maint_print_c_tdesc_cmd (const char *args, int from_tty)
     error (_("There is no target description to print."));
 
   if (filename == NULL)
-    error (_("The current target description did not come from an XML file."));
+    {
+      printf_unfiltered (_("The current target description was fetched "
+			   "from the target, using\n'target.xml' as a fake "
+			   "filename.\n\n"));
+      filename = "target.xml";
+    }
 
   std::string filename_after_features (filename);
   auto loc = filename_after_features.rfind ("/features/");
@@ -1811,6 +1816,8 @@ void _initialize_target_descriptions ();
 void
 _initialize_target_descriptions ()
 {
+  cmd_list_element *cmd;
+
   tdesc_data = gdbarch_data_register_pre_init (tdesc_data_init);
 
   add_basic_prefix_cmd ("tdesc", class_maintenance, _("\
@@ -1842,11 +1849,10 @@ Unset the file to read for an XML target description.\n\
 When unset, GDB will read the description from the target."),
 	   &tdesc_unset_cmdlist);
 
-  add_cmd ("c-tdesc", class_maintenance, maint_print_c_tdesc_cmd, _("\
+  cmd = add_cmd ("c-tdesc", class_maintenance, maint_print_c_tdesc_cmd, _("\
 Print the current target description as a C source file."),
 	   &maintenanceprintlist);
-
-  cmd_list_element *cmd;
+  set_cmd_completer (cmd, filename_completer);
 
   cmd = add_cmd ("xml-descriptions", class_maintenance,
 		 maintenance_check_xml_descriptions, _("\
-- 
2.25.4