Re: Should tiny utilities be prepackaged?

[Daurnimator <quae@...>]

On 2 March 2016 at 05:37, Sean Conner <sean@conman.org> wrote:
> It was thus said that the Great Daurnimator once stated:
>>
>> If we *do* want to talk about standardisation, I'd like to take it in
>> the direction of common OS data structures being portable between
>> libraries (to pick on an example of mine from another thread:
>> sigset_t).
>
>   It being this message, http://lua-users.org/lists/lua-l/2015-09/msg00331.html,
> right?  I'm looking over my own code in org.conman, and I have the following
> types:
>
>         sigset_t
>         DIR*
>         pollset__t
>         struct sockaddr
>         int
>
> sigset_t, DIR* and struct sockaddr are pretty straightforward (although in
> my case, I have struct sockaddr, struct sockaddr_in, struct sockaddr_in6 and
> struct sockaddr_un as a union).

OT: always allocate a struct sockaddr_storage

> The pollset__t is my own invention and
> hides the implementation of select()---on Linux, I actually use
> epoll_wait(), and for other Unix systems, poll() (and I do have a version
> based on select(), but only to be complete).  The lone 'int' is wrapped for
> socket handling.
>
> But then you said:
>
>> The key thing I counted on is that we have the same **ABI** per registry
>> key. i.e. that `sigset_t *set = luaL_checkmeta(L, n, "sigset_t")` will
>> always result in a valid sigset_t pointer.
>
>   First, I'm not sure if doing
>
>         sigset_t *set = luaL_checkmeta(L,n,"sigset_t");
>
> buys you much; I can only think of contrived circumstances where you have
> two different libraries providing signal sets where that would be an issue.

The aim is that a user could create a sigset_t with your library; and
safely pass it to other libraries.
e.g. https://github.com/daurnimator/lua-spawn/blob/6b78e89bece7cc6a64a3bd74ba6ca255edf1eaa5/spawn/posix.c#L123

I picked sigset_t as my example, as it's used across a wide variety of
different syscalls from different "verticals" (lacking a better word).
e.g. you might want to pass a sigset_t to:
  - A classic signal handling library
  - A scheduling library (for ppoll/pselect/epoll_pwait)
  - A threading library (pthread_sigmask)
  - A spawning library (see above lua-spawn example)


> Now, by ABI, do you also mean metamethods?

No. I consider that API vs ABI
I think it's good to have alternative implementations with different
methods and utilities available.
But it sure would be great that you can pass things from one library to another