Re: RFA/ARM: Switch mode when setting PC

Andrew Cagney
2004-01-16T18:57:50Z

> On Fri, Jan 16, 2004 at 09:10:40AM -0500, Daniel Jacobowitz wrote:
>
>> > The ari contains this yellow card:
>> >
>> > write pc
>> > Replace write_pc() with get_frame_base_address or get_frame_id; at
>> > present the inferior function call code still uses this when doing a
>> > DECR_PC_AFTER_BREAK
>> >
>> > the concern is with the way write_pc is being called to perform two
>> > different operations:
>> >
>> > - decrement the pc just after the target stops
>> > Arrrg!
>> > - jump to a specific address
>> > As with an inferior function call or jump.
>> >
>> > I think it would be better to have two methods so that it's clear that
>> > this case only applies when doing a jump.
>
>>
>> Well, it'd be better to rip out the current DECR_PC_AFTER_BREAK and
>> handle it completely within the four (roughly) affected targets,
>> thereby removing the overloading of write_pc. IMVHO.

It's been on everyones wish list for too long. Last time I tried I got
bogged down due to a lack of ia32 doco - that's now been fixed though.

> Hi Andrew,
>
> Is this patch OK (write_pc isn't deprecated yet!)? Cleaning up the
> existing DECR_PC_AFTER_BREAK handling is going to be a touchy job, and
> I don't really want to try it today :) I'll try to look into it later,
> though.

I was suggesting "two methods so that it's clear that this case only
applies when doing a jump". This won't involve anything like
deprecating /removing decr_pc_after_break _+ write_pc but will involve
the addition of a new method like:
set_resume_address (arch, targ or tpid or regs)
that could somehow default to a legacy call to write_pc. Significantly,
this will avoid making the changes conditional on the elimination of
decr-pc (your concern).

Why is this better? It clearly separates the [apparently] legetimate
resume case from the decr-pc case. This in turn opens the way for the
deprecate / delete decr-pc "write_pc" code while at the same time
ensuring that the work can't break the arm.

enjoy,
Andrew