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Re: two agent expression nits (one line each)
- From: Joel Brobecker <brobecker at adacore dot com>
- To: Stan Shebs <stanshebs at earthlink dot net>
- Cc: David Taylor <dtaylor at emc dot com>, "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>
- Date: Sat, 13 Dec 2014 08:44:28 -0500
- Subject: Re: two agent expression nits (one line each)
- Authentication-results: sourceware.org; auth=none
- References: <14583 dot 1410458050 at usendtaylorx2l> <547E24E5 dot 8050908 at earthlink dot net>
Hi Stan,
> > The @item line and the following text do no agree with one another. I'm
> > guessing that the text is correct, in which case this line:
> >
> > @item @code{setv} (0x2d) @var{n}: @result{} @var{v}
> >
> > should be changed to this:
> >
> > @item @code{setv} (0x2d) @var{n}: @var{v} @result{} @var{v}
>
> Yes, that is correct.
>
> > Additionally, in gdb/common/ax.def we find the line:
> >
> > DEFOP (setv, 2, 0, 0, 1, 0x2d)
> >
> >>From the comment earlier in the file:
> >
> > Each line is of the form:
> >
> > DEFOP (name, size, data_size, consumed, produced, opcode)
> > [...]
> > CONSUMED is the number of stack elements consumed.
> > PRODUCED is the number of stack elements produced.
> >
> > which is saying that nothing is consumed and one item is produced. Both
> > should be 0 or both should be 1. Setting them both to 1 seems better
> > since if nothing is on the stack an error will occur. So, it should be
> > changed to:
> >
> > DEFOP (setv, 2, 0, 1, 1, 0x2d)
>
> Yes to this also. From the look of things, I cloned the getv definition
> and forgot to adjust it.
>
> Although technically an incompatible change to the bytecode language,
> anybody who tried to set a state variable within a larger expression was
> going to get odd behavior and/or stack overflow, while the common
> case of just setting the variable and discarding the result is
> unaffected. So I think we can just make the change directly, and
> perhaps add a brief note to NEWS, to make sure that target agents
> get updated. (Mentor has one in-house separate from gdbserver, plus at
> least two customers with their own agents.)
Would you mind taking care of that for us? I kept that message around
in the hope that I'd have a clearer picture with a little extra time,
but I am still not sure whether you're just suggesting a documentation
fix, or if you're saying we should fix the implementation...
Thanks!
--
Joel