[swift-evolution] pitch: Unified libc import (again)

[Taylor Swift]

I don’t think the “is this library functionality or standard library
functionality” argument is worth having, but if stdout and stdin are
first-class citizens in the Swift world, so should stderr.

As for bringing Foundation into the discussion, you can’t really talk about
Foundation without also talking about the mountains of problems that come
with the monolith pattern. But that’s a completely different conversation
to be had.

On Thu, Aug 17, 2017 at 7:13 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:

> IMO, you’re touching on at least three or four separate topics here.
> Daniel touched on several, but just some comments/questions:
>
> * Standard error output is something that’s been discussed here
> previously. I believe the last pitch had something like StandardError being
> added to the standard library as a TextOutputStream.
>
> * Foundation is supposed to be the core library that provides file system
> access facilities. What’s missing, and can we add it to Foundation?
>
> On Thu, Aug 17, 2017 at 17:50 Taylor Swift via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> Python’s os.path <https://docs.python.org/2/library/os.path.html> is a
>> nice abstract model for doing path manipulations. Maybe Swift could get a
>> struct like `Filepath` or something on which these operations could be done.
>>
>> On Thu, Aug 17, 2017 at 6:47 PM, Taylor Swift <kelvin13ma at gmail.com>
>> wrote:
>>
>>>
>>>
>>> On Thu, Aug 17, 2017 at 3:50 PM, Daniel Dunbar <daniel_dunbar at apple.com>
>>> wrote:
>>>
>>>>
>>>> > On Aug 17, 2017, at 9:26 AM, Taylor Swift via swift-evolution <
>>>> swift-evolution at swift.org> wrote:
>>>> >
>>>> > I know this has come up before without any action, but having the
>>>> standard C library be packaged under `Darwin` on OSX and `Glibc` under
>>>> Linux is something that’s really becoming an issue as the Swift package
>>>> ecosystem matures. Right now a lot of packages are a lot less portable than
>>>> they could be because somewhere along the dependency line, there is a
>>>> package that only imports the C library for one platform. Unifying it under
>>>> one import would allow people to write packages that are portable by
>>>> default.
>>>>
>>>> What we (SwiftPM) have done for now is use a `libc` target to start by
>>>> normalizing the name:
>>>>   https://github.com/apple/swift-package-manager/tree/
>>>> master/Sources/libc
>>>> (and in the past, when we find missing things in Glibc getting them
>>>> added to the compiler). Also, this name is technically a misnomer, but we
>>>> couldn’t think of a better one (“os” might have been a good one).
>>>>
>>>> Unfortunately, I think this change alone is really only the tip of the
>>>> iceberg. It would be nice to not have it the difference, but we found we
>>>> very quickly needed several other layers on top to get to having a
>>>> relatively stable cross-platform base:
>>>>   https://github.com/apple/swift-package-manager/tree/
>>>> master/Sources/POSIX
>>>>   https://github.com/apple/swift-package-manager/tree/
>>>> master/Sources/Basic
>>>>
>>>> My hope is that one minimal improvement we can get soon is
>>>> multi-package repo support in SwiftPM, which will at least allow us to
>>>> share those targets & functionality with other packages.
>>>>
>>>> > Since I think this got hung up in the past over “what constitutes” a
>>>> universal libc, I propose a unified package should just consist of the
>>>> functionality that is common between Darwin and Glibc right now, since
>>>> those are the only two supported platforms anyway.
>>>>
>>>> What would the concrete proposal be? It isn’t trivial to determine that
>>>> subset and make it well-defined what the exact API is. Is the proposal to
>>>> just to pick a standard name, and reexport Darwin and Glibc from it?
>>>>
>>>
>>> I don’t know if it’s actually this simple, but could it just be the
>>> symbols that are defined in both modules?
>>>
>>>
>>>>
>>>> > Alternatively, Swift could make it a priority to get basic
>>>> functionality like file IO and math functions shipped with the compiler,
>>>> which would probably cover 98% of cases where people currently import
>>>> Darwin/Glibc. A large portion of the standard C libraries are redundant to
>>>> the Swift standard library anyway.
>>>>
>>>> I’m not sure I agree with these statements about the percentages. For
>>>> some clients (I’m biased, the areas I work in tend to be in this boat),
>>>> what we largely need is good platform-agnostic access to the POSIX APIs.
>>>> This is a hard problem to make a good cross-platform API for (esp. if
>>>> Windows support is in your head), and which many projects struggle with
>>>> (Netscape :: NSPR, LLVM :: libSupport, many many more).
>>>>
>>>> The sticking point I see is this: if the proposal is just to unify the
>>>> name & that doesn’t actually buy us all that much (still need standard
>>>> layers on top), then have we really solved enough of a problem to be worth
>>>> standardizing on?
>>>>
>>>> +1 in general agreement with the meta-issue being an important one to
>>>> discuss.
>>>>
>>>
>>> There probably is an XY issue at play here; what we *really* need is a
>>> way to access the file system built into the standard library. (Math
>>> functions are a separate, beleaguered topic for a different thread.) Having
>>> support for outputting to `stderr` is also something I’d really like. Going
>>> through Glibc/Darwin is just one way to solve this.
>>>
>>
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>
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