[swift-users] System Modules and pkgConfig

[Etan Kissling]

Addition:

Example system module as I have it now:
https://github.com/Scriptreactor/SwiftCTLS

I'd like to get rid of the absolute path in the module.modulemap's "header" directive and have it instead use pkgConfig values.



> On 28 Dec 2016, at 17:12, Etan Kissling via swift-users <swift-users at swift.org> wrote:
> 
> Hi,
> 
> before Swift 3, for System Modules to work, these steps were necessary:
> 1. Creating module map
> 2. Creating System Module package
> 3. Creating git repo for System Module package, tagging with version
> 4. Referencing the System Module package from main package
> 5. Adding -Xcc -I and -Xlinker -L flags to the swift build command.
> 
> The problem here is, that absolute system-depending paths are required at:
> - module map "header" entry.
> - Xcc -I flag when building.
> - Xlinker -L flag when building.
> 
> To solve this, Swift 3 introduced support for System Module search paths:
> https://github.com/apple/swift-evolution/blob/master/proposals/0063-swiftpm-system-module-search-paths.md
> 
> In my case, I end up with the following for the System Module package:
> 
> module CFoo [system] {
>  header "/system/depending/path/to/my/header.h"
>  link "foo"
>  export *
> }
> 
> 
> import PackageDescription
> 
> let package = Package(
>    name: "CFoo",
>    pkgConfig: "foo",
>    providers: [
>        .Brew("foo")
>    ]
> )
> 
> 
> With this setup, I can run
> PKG_CONFIG_PATH=/system/depending/path/to/my/pc/file swift build
> and build the project without specifying custom Xcc -I / Xlinker -L flags.
> 
> However, the absolute system-depending path is still required in the modulemap.
> 
> When I change the module map to
> 
> module CFoo [system] {
>  header "header.h"
>  link "foo"
>  export *
> }
> 
> , I get build errors like
> 
> /module.modulemap:2:##: error: header 'header.h' not found
> 
> This is kind of different than what is suggested by the proposal (that it should recommend installing via Brew / Apt in that case).
> 
> 
> ==> How do I need to set up the project so that system-depending paths are required at no point?
> ==> Is there an example project available on github that demonstrates the pkgConfig feature of SwiftPM?
> 
> 
> Thanks
> 
> Etan
> 
> 
> 
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