Re: RFA: remote_address_size changes

[Kevin Buettner <kevinb at cygnus dot com>]

On Nov 4,  8:57am, Andrew Cagney wrote:

> Have a look at how remote.c registers and then updates the variable
> tty_input.  When ever the user selects a new target, that variable is
> switched (brutal yes).
> 
> For remote_address_size you would probably want to do something similar.

I agree.  I've appended a new patch for you to look at below.

[...]
> The above mechanism binds ``remote_address_size'' to the architecture. 
> If the architecture changes - new binary of a different type then the
> old selection is lost.  Is this a good thing or a  dangerous thing?
> 
> Consider the sequence:
> 
> 	set remote address-size 16
> 	file xyz
> 
> which can have different semantics to:
> 
> 	file xyz
> 	set remote address-size 16
> 
> Making their behavour identical isn't trivial (fortunatly it isn't
> difficult either).  The problem is figuring out exactly what reasonable
> behavour is - I have no opinion.

I don't (necessarily) see a problem with overriding the users setting
in the following scenario.

 	set remote address-size 16
 	file xyz

Consider the following (more ambiguous) scenario:

 	file xyz
	...
 	set remote address-size 16
	...
 	file zyx

I think there will be situations where it definitely makes sense for
"file zyx" to cause a different remote_address_size to be set.  There
are also situations where it doesn't make sense; I think it will be
difficult to intelligently disabmiguate them.  In situations like
this, maybe it would make sense to warn the user when setting a new
target causes the user's setting to be overridden.  (Unfortunately,
this means that we have to keep track of whether or not the user set a
variable or not.)

Now on to the matter of naming...  I like the command names that you
used in your example sequences, e.g,

 	set remote address-size 16

But, at present, this notation doesn't work.  Instead you have to do

	set remoteaddresssize 16

I think we should add an alias so the notation in your examples will
work as well.  Also, I think your memory-{read,write}-packet-size
names are fine.  (It's a good thing we have name completion though, or
I might not like them so well.)

Here's the patch...

	* remote.c (build_remote_gdbarch_data): Set remote_address_size...
	(_initialize_remote) ...but don't set it here.  Also, tie
	remote_address_size to the target architecture via call to
	register_gdbarch_swap().

Index: remote.c
===================================================================
RCS file: /cvs/cvsfiles/devo/gdb/remote.c,v
retrieving revision 1.255
diff -u -r1.255 remote.c
--- remote.c	1999/11/04 11:04:51	1.255
+++ remote.c	1999/11/04 20:31:39
@@ -5221,6 +5221,7 @@
 build_remote_gdbarch_data ()
 {
   tty_input = xmalloc (PBUFSIZ);
+  remote_address_size = TARGET_PTR_BIT;
 }
 
 void
@@ -5232,6 +5233,8 @@
   /* architecture specific data */
   build_remote_gdbarch_data ();
   register_gdbarch_swap (&tty_input, sizeof (&tty_input), NULL);
+  register_gdbarch_swap (&remote_address_size, 
+                         sizeof (&remote_address_size), NULL);
   register_gdbarch_swap (NULL, 0, build_remote_gdbarch_data);
 
   /* runtime constants - we retain the value of remote_write_size
@@ -5305,7 +5308,6 @@
 		  &setlist),
      &showlist);
 
-  remote_address_size = TARGET_PTR_BIT;
   add_show_from_set
     (add_set_cmd ("remoteaddresssize", class_obscure,
 		  var_integer, (char *) &remote_address_size,