[swift-users] [swift-build-dev] Importing C system libraries

[Ankit Aggarwal]

In this case, these are just umbrella headers. If your modulemap contains absolute path to the header, then you don't need the header files, but SwiftPM will probably warn about this. Note that this is a "hack" to have system packages inside a single repository. The correct way is to have system package as a separate published package which you only need to do once.

> On 29-Mar-2017, at 10:26 AM, Kelvin Ma <kelvinsthirteen at gmail.com> wrote:
> 
> I will try this, but why are the header files inside the Sources directory? System headers should live in /usr/include…
> 
> On Tue, Mar 28, 2017 at 11:48 PM, Ankit Aggarwal <ankit_aggarwal at apple.com <mailto:ankit_aggarwal at apple.com>> wrote:
> Hi,
> 
> Apologies for not replying to this earlier. 
> 
> You can have multiple targets in a single package. Each target can either be Swift or C-family. The type of target is determined by the sources contained in it (*.c/*.cpp etc means C target, *.swift means Swift target). So if you want to create multiple C targets, this layout should work:
> 
> Package.swift
> Sources/
>     Bitmap
>     Cubify
>     Cairo/anchor.c <---- This is just an empty file to tell SwiftPM that this is a C target.
>     Cairo/include/Cairo.h
>     Cairo/include/module.modulemap
>     GLFW/anchor.c
>     GLFW/include/GLFW.h
>     GLFW/include/module.modulemap
> 
> The modulemap is automatically generated, if not provided. This is a package which contains two targets (one C and one Swift): https://github.com/jpsim/Yams <https://github.com/jpsim/Yams>
> 
> If you need to pass a bunch of compiler flags, you can use SwiftPM's pkgConfig feature but that will require you to have a separate repository for Cario and GLFW. You can experiment without creating tags using the edit feature <https://github.com/apple/swift-package-manager/blob/master/Documentation/Usage.md#editable-packages>.
> 
> PS: You can join SwiftPM slack channel for quicker turn around time: https://lists.swift.org/pipermail/swift-build-dev/Week-of-Mon-20160530/000497.html <https://lists.swift.org/pipermail/swift-build-dev/Week-of-Mon-20160530/000497.html>
> 
> Thanks,
> Ankit
> 
> 
> On Wed, Mar 29, 2017 at 6:06 AM, Michael Ilseman via swift-build-dev <swift-build-dev at swift.org <mailto:swift-build-dev at swift.org>> wrote:
> This is into uncharted territory for me, but it seems you’re building with SwiftPM. You’ll probably want to configure extra compiler flags if that’s possible. You could also bite the bullet and build your C libraries with SwiftPM as well. Hopefully someone on swift-build-dev can help you out.
> 
> CC-ing Ankit
> 
> 
>> On Mar 28, 2017, at 5:09 PM, Kelvin Ma <kelvinsthirteen at gmail.com <mailto:kelvinsthirteen at gmail.com>> wrote:
>> 
>> How do I compile a project with many modules? My tree looks like this:
>> 
>> <Selection_001.png>
>> ​
>> 
>> On Tue, Mar 28, 2017 at 12:47 PM, Michael Ilseman <milseman at apple.com <mailto:milseman at apple.com>> wrote:
>> Sure! In this example, I have built libgit2. I have a directory called Git, and inside that I have the following module map:
>> 
>> module Git [system] {
>>        header "<my path>/libgit2/include/git2.h"
>>        export *
>> }
>> 
>> When I run, I use:
>> 
>> swift -I <path-to-“Git”-directory> -L <path-to-built-libgit2> -lgit2 foo.swift
>> 
>> inside foo.swift I can:
>> 
>> import Git
>> // … use libGit2
>> 
>> 
>> Read more about how to write a more appropriate module.map file for your purposes at https://clang.llvm.org/docs/Modules.html <https://clang.llvm.org/docs/Modules.html>. For example, you might be able to define link flags inside the module.map, use umbrella directories, submodules, etc.
>> 
>> 
>> 
>>> On Mar 28, 2017, at 6:27 AM, Kelvin Ma <kelvinsthirteen at gmail.com <mailto:kelvinsthirteen at gmail.com>> wrote:
>>> 
>>> Can you give an example?
>>> 
>>> On Mon, Mar 27, 2017 at 3:59 PM, Michael Ilseman <milseman at apple.com <mailto:milseman at apple.com>> wrote:
>>> Sure. At a low level, you can create a module.map file and use -L/-l flags in your invocation of Swift. If you want to do so at a higher level, then perhaps SwiftPM can. CCing swift-build-dev for the SwiftPM part.
>>> 
>>> 
>>> > On Mar 26, 2017, at 3:20 PM, Kelvin Ma via swift-users <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>>> >
>>> > Idk if this has been asked before, but is there a way to import C libraries into a Swift project without creating a local git repo? Preferably something similar to C where you can just `#include` headers and then specify the link flags (in Package.swift?)
>>> >
>>> > It’s getting very cumbersome to make a bunch of empty git repos just to use libglfw or libcairo.
>>> > _______________________________________________
>>> > swift-users mailing list
>>> > swift-users at swift.org <mailto:swift-users at swift.org>
>>> > https://lists.swift.org/mailman/listinfo/swift-users <https://lists.swift.org/mailman/listinfo/swift-users>
>>> 
>>> 
>> 
>> 
> 
> 
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