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Re: [PATCH v2] Add Guile frame unwinder interface
- From: Andy Wingo <wingo at igalia dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: gdb-patches at sourceware dot org, asmundak at google dot com
- Date: Mon, 09 Mar 2015 19:54:27 +0100
- Subject: Re: [PATCH v2] Add Guile frame unwinder interface
- Authentication-results: sourceware.org; auth=none
- References: <87oao7wi66 dot fsf at igalia dot com> <87zj7msbly dot fsf at igalia dot com> <54FDBF21 dot 4090400 at redhat dot com>
Hi,
On Mon 09 Mar 2015 16:41, Pedro Alves <palves@redhat.com> writes:
> On 03/09/2015 10:34 AM, Andy Wingo wrote:
>> +@var{register} names a register, and should be a string, for example
>> +@samp{rip}. @var{value} is the register value, as a @value{GDBN}
>> +value. Alternately, passing @code{#f} as the value will mark the
>> +register as unavailable.
>
> From a glimpse over the code, I think this actually marks it as
> "<not saved>" (optimized out), right? That would be the correct
> thing to do. Marking a register as "<unavailable>" is also possible,
> but it is a different thing -- it means the value exists, but gdb
> couln't get to it, because e.g., the core file is trimmed, or the
> ptrace interface is missing access to some registers.
>
> That said, you may want to consider how you'd expand the API
> to allow marking registers as unavailable.
I didn't realize that "unavailable" and "not saved" were different
things, thanks for the pointer. I guess given that the default is a
"not saved" result, I can just document this default state, and that
ephemeral-frame-add-saved-value! adds a value. We remove the #f case.
If we need to support other states like "unavailable", we can add other
API like ephemeral-frame-mark-unavailable! or similar.
>> + is_unwinding = 1;
>> TRY_CATCH (ex, RETURN_MASK_ERROR)
>> {
>> res = unwinder->sniffer (unwinder, this_frame, this_cache);
>> }
>> + is_unwinding = 0;
>
> Note that RETURN_MASK_ERROR does not catch all exceptions (notably,
> a ctrl-c/QUIT passes right through uncaught).
Ah indeed. I'll move the is_unwinding=1 to a cleanup inside the TRY_CATCH.
Thanks for the review,
Andy