remote: call remote_check_symbols after attaching

When debugging a remote bare-metal target with "target
extended-remote" + attach, GDB won't send a qSymbol packet to initiate
symbol lookup.  This happens because all the previous places in which
GDB might have done this are guarded by conditions that don't hold in
the said scenario: there are no shared libraries, no vsyscall page and
the binary file didn't change in the time passed between the "file"
and the "attach" commands.

To solve this problem remote_check_symbols is called in the
target_post_attach hook.

gdb/
2014-07-11  Adrian Sendroiu  <[email protected]>

	* remote.c (extended_remote_post_attach): New function.
	(init_extended_remote_ops): Install it as to_post_attach method.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2014-07-11  Adrian Sendroiu  <[email protected]>
+
+	* remote.c (extended_remote_post_attach): New function.
+	(init_extended_remote_ops): Install it as to_post_attach method.
+
 2014-07-09  Pedro Alves  <[email protected]>
 
 	* infcmd.c (attach_command_post_wait): Don't call

gdb/remote.c

@@ -4484,6 +4484,20 @@ extended_remote_attach (struct target_ops *ops, const char *args, int from_tty)
   extended_remote_attach_1 (ops, args, from_tty);
 }
 
+/* Implementation of the to_post_attach method.  */
+
+static void
+extended_remote_post_attach (struct target_ops *ops, int pid)
+{
+  /* In certain cases GDB might not have had the chance to start
+     symbol lookup up until now.  This could happen if the debugged
+     binary is not using shared libraries, the vsyscall page is not
+     present (on Linux) and the binary itself hadn't changed since the
+     debugging process was started.  */
+  if (symfile_objfile != NULL)
+    remote_check_symbols();
+}
+
 
 /* Check for the availability of vCont.  This function should also check
    the response.  */
@@ -11530,6 +11544,7 @@ Specify the serial device it is connected to (e.g. /dev/ttya).";
   extended_remote_ops.to_mourn_inferior = extended_remote_mourn;
   extended_remote_ops.to_detach = extended_remote_detach;
   extended_remote_ops.to_attach = extended_remote_attach;
+  extended_remote_ops.to_post_attach = extended_remote_post_attach;
   extended_remote_ops.to_kill = extended_remote_kill;
   extended_remote_ops.to_supports_disable_randomization
     = extended_remote_supports_disable_randomization;