Re: bug#24514: 24.5; Lispy backtraces

["Clément Pit--Claudel" <clement.pit@gmail.com>]

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On 2016-12-04 10:30, Eli Zaretskii wrote:
>> From: Clément Pit--Claudel <clement.pit@gmail.com>
>> Date: Sat, 3 Dec 2016 17:15:22 -0500
>>
>> On 2016-12-01 21:24, Stefan Monnier wrote:
>>>> The discussion below seems to indicate that there's very little missing at
>>>> the Lisp level to be able to implement `backtrace' in Lisp; is that right?
>>>
>>> Indeed, I think all the info needed is provided by backtrace-frame.
>>
>> The C implementation of backtrace-frame seems to be linear in the index of the requested frame, so a Lisp implementation of backtrace would be quadratic in the depth of the stack trace.  Would a new function backtrace-frames that returns all frames at once be acceptable?
> 
> But such a backtrace-frames function would have to be implemented in
> C, right?  And you wanted to move the implementation of "backtrace" to
> Lisp, AFAIU.  So it sounds like we will be replacing one C primitive
> with another, or did I miss something?

I think you're correct. It would seem good to have the flexible primitive backtrace-frames available, and it must be in C; then we can move backtrace itself to lisp.

The idea is that enumerating frames must be done in C, but printing them doesn't need to be done there.

Clément.


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