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Re: Overriding uiout
- From: Andrew Cagney <ac131313 at ges dot redhat dot com>
- To: Daniel Jacobowitz <drow at mvista dot com>
- Cc: gdb at sources dot redhat dot com
- Date: Tue, 23 Jul 2002 16:05:27 -0400
- Subject: Re: Overriding uiout
- References: <20020723164601.GA23869@nevyn.them.org>
There are currently only four code paths in the entire GDB source tree where
uiout could theoretically be overridden to something other than the normal
uiout. They're all for libgdb: gdb_value_struct_elt, gdb_thread_select,
gdb_list_thread_ids, and gdb_breakpoint_query. The only place it actually
appears to be overridden is in gdb_value_struct_elt, which is occasionally
called from varobj code with uiout==NULL. Otherwise it is always overridden
to itself.
The -interpreter-exec command needs it. See:
http://sources.redhat.com/ml/gdb/2002-05/msg00177.html
This overriding mechanism makes it a bit awkward to redirect GDB's output;
any change to uiout is lost after the current command if we are running from
the prompt (although, surprisingly and IMO inconsistently, it lasts until
the end of a user-defined function).
That is likely something that -interpreter-exec is going to have to
flush out.
So I'll ask again - what is this interface supposed to accomplish? If it's
just a step down the road to passing explicit state everywhere, then I think
it's a significant step backwards in other ways, and that we should instead
let clients or wrapper functions manipulate the global state until we're
truly ready to pass a global state around - a global state which can be
overridden for this sort of task.
It's a step down the road of passing explict I/O re-direction. It will
likely be finished when GDB starts passing more global state around.
As I mentioned in another e-mail you need to ensure that the assertion:
global uiout->stream == global gdb_stdout et.al.
holds. There are a number of ways of doing this short term. Replacing
gdb_stdout with a function is one, blatting the global is another.
This is purely a design question, not an implementation objection. For
implementation I'm restricting this feature to CLI only, and implementing it
within cli-out. It turned out to be more elegant than I expected.
Andrew