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Date: Fri, 17 Feb 2006 10:22:00 -0000
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From: Eli Zaretskii <eliz@gnu.org>
To: Vladimir Prus <ghost@cs.msu.su>
CC: gdb@sources.redhat.com
In-reply-to: <dt43qh$sns$1@sea.gmane.org> (message from Vladimir Prus on Fri, 	17 Feb 2006 12:08:32 +0300)
Subject: Re: MI: type prefixes for values
Reply-to: Eli Zaretskii <eliz@gnu.org>
References:  <dt43qh$sns$1@sea.gmane.org>
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> From:  Vladimir Prus <ghost@cs.msu.su>
> Date:  Fri, 17 Feb 2006 12:08:32 +0300
> 
> some time ago I've raised the question why MI output sometimes prefixes
> variable values with it's type. For example:
> 
>    -data-evaluate-expression *p3
>    ^done,value="{int (int)} 0xb7ee6e9c <__DTOR_END__+4>"
>    (gdb)
> 
> (note the {int (int)} part). The part does not make sense for a GUI and must
> be removed by a specially written code.
> 
> See:
> 
>    http://article.gmane.org/gmane.comp.gdb.devel/13477

And you were answered in that thread that this prefix is to show you
the signature of a function to which p3 is a pointer.  That is, GDB is
telling you that p3 points to a function which accepts a single int
argument and returns an int.

> In the end, I've inquired why such prefixes cannot be dropped:
> 
>   http://article.gmane.org/gmane.comp.gdb.devel/13539

Are you saying that you don't want to show your users the fact that
the pointed object is a function?

> I imagine it's a simple matter of wrapping some code in
> "ui_output_is_mi_like_p". Can somebody comment on this proposal?

I think this will lose useful information.  So for now I object.

> Also, I note that gdb is currently inconsitent even within itself:
> 
>     (gdb)
>     -thread-select 2
>     ^done,new-thread-id="2",frame={level="0",func="thread",
>     args=[{name="p",value="0x0"}],..........
>    (gdb)
>    -stack-list-arguments 1 0 0
>    ^done,stack-args=[frame={level="0",
>    args=[{name="p",value="(void *) 0x0"}]}]
> 
> Note that first output has "0x0" as value of 'p', and the second has 
> "(void *)0x0". 

Also, the first one shows the func= part, the second doesn't.  Looks
like a bug to me: those two should both use the same code.

> So, can a clear decision be made if the type prefixes has a place in MI, or
> should be removed?

At least for functions, they convey useful information.