Re: Proposal/Discussion: Turning parts of Git into libraries

[Felipe Contreras <felipe.contreras@gmail.com>]

On Thu, Mar 23, 2023 at 5:30 PM <rsbecker@nexbridge.com> wrote:
>
> On Thursday, March 23, 2023 7:22 PM, Felipe Contreras wrote:
> >On Sat, Feb 18, 2023 at 5:12 AM Phillip Wood <phillip.wood123@gmail.com> wrote:
> >>
> >> On 18/02/2023 01:59, demerphq wrote:
> >> > On Sat, 18 Feb 2023 at 00:24, Junio C Hamano <gitster@pobox.com> wrote:
> >> >>
> >> >> Emily Shaffer <nasamuffin@google.com> writes:
> >> >>
> >> >>> Basically, if this effort turns out not to be fruitful as a whole,
> >> >>> I'd like for us to still have left a positive impact on the codebase.
> >> >>> ...
> >> >>> So what's next? Naturally, I'm looking forward to a spirited
> >> >>> discussion about this topic - I'd like to know which concerns
> >> >>> haven't been addressed and figure out whether we can find a way
> >> >>> around them, and generally build awareness of this effort with the community.
> >> >>
> >> >> On of the gravest concerns is that the devil is in the details.
> >> >>
> >> >> For example, "die() is inconvenient to callers, let's propagate
> >> >> errors up the callchain" is an easy thing to say, but it would take
> >> >> much more than "let's propagate errors up" to libify something like
> >> >> check_connected() to do the same thing without spawning a separate
> >> >> process that is expected to exit with failure.
> >> >
> >> >
> >> > What does "propagate errors up the callchain" mean?  One
> >> > interpretation I can think of seems quite horrible, but another
> >> > seems quite doable and reasonable and likely not even very invasive
> >> > of the existing code:
> >> >
> >> > You can use setjmp/longjmp to implement a form of "try", so that
> >> > errors dont have to be *explicitly* returned *in* the call chain.
> >> > And you could probably do so without changing very much of the
> >> > existing code at all, and maintain a high level of conceptual
> >> > alignment with the current code strategy.
> >>
> >> Using setjmp/longjmp is an interesting suggestion, I think lua does
> >> something similar to what you describe for perl. However I think both
> >> of those use a allocator with garbage collection. I worry that using
> >> longjmp in git would be more invasive (or result in more memory leaks)
> >> as we'd need to to guard each allocation with some code to clean it up
> >> and then propagate the error. That means we're back to manually
> >> propagating errors up the call chain in many cases.
> >
> >We could just use talloc [1].
>
> talloc is not portable.

What makes you say that?

Either way, there's multiple libraries that do the same thing, and of
course one could be implemented within Git. It's not that complex.

-- 
Felipe Contreras