[swift-corelibs-dev] libdispatch on Linux, or C++ std::async?

Brian Croom brian.s.croom at gmail.com
Mon May 30 19:39:38 CDT 2016 

I have no hands-on experience with it itself, but my understanding is that
the std::async API in the current standards is pretty severely flawed and
makes it awfully easy to shoot yourself in the foot. On the other hand, the
libdispatch usage here does appear to be pretty basic.

Hopefully someone with more expertise can weigh in still!

måndag 30 maj 2016 skrev Brian Gesiak via swift-corelibs-dev <
swift-corelibs-dev at swift.org>:

> Gah, thanks Brian and Chris -- yes, I had forgotten. I initialized it once
> on a separate development environment and forgot to do so again.
>
> Thanks everyone! I managed to build the project. :)
>
> I'll try getting SourceKit to link against my built libdispatch. Does
> anyone have any thoughts on my second question? Would it make sense to move
> SourceKit over to C++ async features? SourceKit only uses the following
> libdispatch symbols:
>
> - dispatch_after
> - dispatch_release
> - dispatch_semaphore_create
> - dispatch_semaphore_signal
> - dispatch_semaphore_wait
> - dispatch_time
>
> As far as I understand, having SourceKit use libdispatch means:
>
> 1. Having libdispatch built as part of all Swift builds that build
> SourceKit. On OS X, most buildbot presets build SourceKit. I'd like to do
> the same for Linux.
> 2. Building libdispatch prior to building Swift, or at least prior to
> building Swift tools like SourceKit.
>
> Moving these build dependencies around seems like more work than using C++
> async, but I barely know C++, so I'm not sure. Thoughts?
>
> - Brian Gesiak
>
>
> On Mon, May 30, 2016 at 12:19 PM, Chris Bailey <BAILEYC at uk.ibm.com
> <javascript:_e(%7B%7D,'cvml','BAILEYC at uk.ibm.com');>> wrote:
>
>> The missing reference is to 'pthread_workqueue_signal_np()' which was
>> added to libpwq via PR #10:
>>         https://github.com/mheily/libpwq/pull/10
>>
>> I suspect that you don't have the libpwq submodule checked out in
>> swift-corelibs-libdispatch. Is there any contents in
>> swift-corelibs-libdispatch/libpwq?
>>
>> If not, running:
>>         git submodule init
>>         git submodule update
>> from the swift-corelibs-libdispatch directory should fix it.
>>
>> Chris
>>
>>
>>
>>
>> From:        Brian Gesiak <modocache at gmail.com
>> <javascript:_e(%7B%7D,'cvml','modocache at gmail.com');>>
>> To:        Chris Bailey/UK/IBM at IBMGB
>> Cc:        Rob Allen <rob at akrabat.com
>> <javascript:_e(%7B%7D,'cvml','rob at akrabat.com');>>, Swift Core Libs <
>> swift-corelibs-dev at swift.org
>> <javascript:_e(%7B%7D,'cvml','swift-corelibs-dev at swift.org');>>
>> Date:        30/05/2016 16:51
>> Subject:        Re: [swift-corelibs-dev] libdispatch on Linux, or C++
>> std::async?
>> ------------------------------
>>
>>
>>
>> Thanks for the quick responses!
>>
>> I had tried the experimental/foundation branch as well, with no luck.
>> Here's the full output from a clean build I just attempted:
>> *https://gist.github.com/modocache/fcf0c78908b39834448c73ac3f50c110*
>> <https://gist.github.com/modocache/fcf0c78908b39834448c73ac3f50c110>
>>
>> Prior to the build I removed my entire build directory (which included
>> both libdispatch-linux-x86_64 and swift-linux-x86_64) and removed all build
>> artifacts from my libdispatch directory (I used `git clean -fxd` -- Make
>> tells me there's no target `distclean`).
>>
>> Looking at the build failure, it appears to be the same one that was
>> reported in *https://bugs.swift.org/browse/SR-1242*
>> <https://bugs.swift.org/browse/SR-1242>. The author of that report
>> indicates that
>> *https://github.com/apple/swift-corelibs-libdispatch/pull/64*
>> <https://github.com/apple/swift-corelibs-libdispatch/pull/64> fixes the
>> problem. My checkout includes the commits from that pull request, but the
>> problem remains.
>>
>> In any case, thanks for all your help! I'll keep trying. Any and all
>> advice would be much appreciated!
>>
>> - Brian Gesiak
>>
>>
>> On Mon, May 30, 2016 at 10:22 AM, Chris Bailey <*BAILEYC at uk.ibm.com*
>> <javascript:_e(%7B%7D,'cvml','BAILEYC at uk.ibm.com');>> wrote:
>> I'd certainly recommend picking up the experimental/foundation branch as
>> Rob recommends. Its where we've been doing some additional work to get
>> properly built into the Swift toolchain and to open up some internal APIs
>> needed by Foundation.
>>
>> Whilst I've been building Dispatch either independently or as part of a
>> full toolchain using the buildbot_linux preset (with dispatch and
>> install-dispatch added), I've just checked your build line and its working
>> fine for me. It might be worth cleaning out any partial build you might
>> have of libdispatch in your build directory, and running 'make distclean'
>> from your libdispatch source directory.
>>
>> FYI, we've got some further changes to the experimental/foundation branch
>> of libdispatch with should land in the next couple of days. This fixes some
>> issues with the Swift overlay, and resolves a crash that we've found in the
>> underlying libkqueue implementation.
>>
>> Chris
>>
>>
>>
>>
>> From:        Rob Allen via swift-corelibs-dev <
>> *swift-corelibs-dev at swift.org*
>> <javascript:_e(%7B%7D,'cvml','swift-corelibs-dev at swift.org');>>
>> To:        Brian Gesiak <*modocache at gmail.com*
>> <javascript:_e(%7B%7D,'cvml','modocache at gmail.com');>>
>> Cc:        Swift Core Libs <*swift-corelibs-dev at swift.org*
>> <javascript:_e(%7B%7D,'cvml','swift-corelibs-dev at swift.org');>>
>> Date:        30/05/2016 08:08
>> Subject:        Re: [swift-corelibs-dev] libdispatch on Linux, or C++
>> std::async?
>> Sent by:        *swift-corelibs-dev-bounces at swift.org*
>> <javascript:_e(%7B%7D,'cvml','swift-corelibs-dev-bounces at swift.org');>
>> ------------------------------
>>
>>
>>
>>
>> Hi,
>>
>> For what it's worth, I can't get the master branch to build either, but I
>> can get the experimental/foundation branch to build.
>>
>> Regards,
>>
>> Rob....
>>
>>
>> On 30 May 2016, at 05:28, Brian Gesiak via swift-corelibs-dev <
>> *swift-corelibs-dev at swift.org*
>> <javascript:_e(%7B%7D,'cvml','swift-corelibs-dev at swift.org');>> wrote:
>>
>> Hello all!
>>
>> I'm working on *https://bugs.swift.org/browse/SR-710*
>> <https://bugs.swift.org/browse/SR-710>, which involves porting SourceKit
>> to Linux. SourceKit contains a handful of references to libdispatch symbols.
>>
>> I have two questions:
>>
>> 1. Could someone share a set of instructions to build
>> swift-corelibs-libdispatch on Linux? I'm using Ubuntu 15.10 and have
>> installed [the dependencies listed here](
>> *https://lists.swift.org/pipermail/swift-corelibs-dev/Week-of-Mon-20151207/000122.html*
>> <https://lists.swift.org/pipermail/swift-corelibs-dev/Week-of-Mon-20151207/000122.html>).
>> I have tried using both `swift/utils/build-script --libdispatch` as well as
>> the instructions in the swift-corelibs-libdispatch `INSTALL` file. Both
>> fail with the [same errors](
>> *https://gist.github.com/modocache/8389d5d64e39ca5a4281500f84e9ce11*
>> <https://gist.github.com/modocache/8389d5d64e39ca5a4281500f84e9ce11>).
>> Any tips?
>>
>> 2. I don't know much about C++, but from what I understand the C++ stdlib
>> provides tools for asynchronous programming. I list SourceKit's uses of
>> libdispatch in a comment on *https://bugs.swift.org/browse/SR-1639*
>> <https://bugs.swift.org/browse/SR-1639>. For those familiar with both
>> C++ and libdispatch: do you think it's a good idea to migrate to C++, at
>> least for now?
>>
>> Any advice would be appreciated. Thanks!!
>>
>> - Brian Gesiak
>>
>>
>> --
>> Development thoughts at *http://akrabat.com* <http://akrabat.com/>
>> Daily Jotter for Mac OS X at *http://dailyjotter.com*
>> <http://dailyjotter.com/>
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>>
>>
>>
>>
>
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