* Makefile.in (SFILES): Add new and missed files.

(target_descriptions_h): New.
	(COMMON_OBS): Add target-descriptions.o.
	(arch-utils.o, infcmd.o, remote.o, target.o): Update.
	(target-descriptions.o): New.
	* arch-utils.c (gdbarch_info_fill): Check for a target
	description.
	* target-descriptions.c, target-descriptions.h: New files.
	* gdbarch.sh: Add target_desc to info.  Declare it in gdbarch.h.
	Correct typos.
	(gdbarch_list_lookup_by_info): Check target_desc.
	* gdbarch.c, gdbarch.h: Regenerated.
	* target.c (update_current_target): Mention to_read_description.
	(target_pre_inferior): Call target_clear_description.
	(target_read_description): New.
	* target.h (struct target_ops): Add to_read_description.
	(target_read_description): New prototype.
	* infcmd.c (post_create_inferior): Call target_find_description.
	* remote.c (remote_open_1): Likewise.
	(extended_remote_create_inferior): Add a comment.
	(extended_remote_async_create_inferior): Likewise.

gdb/target-descriptions.c

@@ -0,0 +1,131 @@
+/* Target description support for GDB.
+
+   Copyright (C) 2006
+   Free Software Foundation, Inc.
+
+   Contributed by CodeSourcery.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110-1301, USA.  */
+
+#include "defs.h"
+#include "arch-utils.h"
+#include "target.h"
+#include "target-descriptions.h"
+
+#include "gdb_assert.h"
+
+/* Types.  */
+
+struct target_desc
+{
+};
+
+/* Global state.  These variables are associated with the current
+   target; if GDB adds support for multiple simultaneous targets, then
+   these variables should become target-specific data.  */
+
+/* A flag indicating that a description has already been fetched from
+   the current target, so it should not be queried again.  */
+
+static int target_desc_fetched;
+
+/* The description fetched from the current target, or NULL if the
+   current target did not supply any description.  Only valid when
+   target_desc_fetched is set.  Only the description initialization
+   code should access this; normally, the description should be
+   accessed through the gdbarch object.  */
+
+static const struct target_desc *current_target_desc;
+
+/* Fetch the current target's description, and switch the current
+   architecture to one which incorporates that description.  */
+
+void
+target_find_description (void)
+{
+  /* If we've already fetched a description from the target, don't do
+     it again.  This allows a target to fetch the description early,
+     during its to_open or to_create_inferior, if it needs extra
+     information about the target to initialize.  */
+  if (target_desc_fetched)
+    return;
+
+  /* The current architecture should not have any target description
+     specified.  It should have been cleared, e.g. when we
+     disconnected from the previous target.  */
+  gdb_assert (gdbarch_target_desc (current_gdbarch) == NULL);
+
+  current_target_desc = target_read_description (&current_target);
+
+  /* If a non-NULL description was returned, then update the current
+     architecture.  */
+  if (current_target_desc)
+    {
+      struct gdbarch_info info;
+
+      gdbarch_info_init (&info);
+      info.target_desc = current_target_desc;
+      if (!gdbarch_update_p (info))
+	warning (_("Could not use target-supplied description"));
+    }
+
+  /* Now that we know this description is usable, record that we
+     fetched it.  */
+  target_desc_fetched = 1;
+}
+
+/* Discard any description fetched from the current target, and switch
+   the current architecture to one with no target description.  */
+
+void
+target_clear_description (void)
+{
+  struct gdbarch_info info;
+
+  if (!target_desc_fetched)
+    return;
+
+  target_desc_fetched = 0;
+  current_target_desc = NULL;
+
+  gdbarch_info_init (&info);
+  if (!gdbarch_update_p (info))
+    internal_error (__FILE__, __LINE__,
+		    _("Could not remove target-supplied description"));
+}
+
+/* Return the global current target description.  This should only be
+   used by gdbarch initialization code; most access should be through
+   an existing gdbarch.  */
+
+const struct target_desc *
+target_current_description (void)
+{
+  if (target_desc_fetched)
+    return current_target_desc;
+
+  return NULL;
+}
+
+/* Methods for constructing a target description.  */
+
+struct target_desc *
+allocate_target_description (void)
+{
+  return XZALLOC (struct target_desc);
+}