How to properly link to DLL on Windows

Using Swift
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1

Hey, Swift noobie here. I want to create a wrapper for SDL3 since the ones that I found online don't support Windows yet. But the process is driving me insane. I have SDL3 downloaded and prebuilt it as a DLL + Lib and headers as follows:

-Dependencies
|   \---SDL3
|       |   module.modulemap
|       |   SDL3.dll
|       |   SDL3.lib
|       |
|       \---SDL3
|               SDL.h
|               * rest of the SDL headers *

My module map is defined as follows:

module CSDL3 [system][extern_c] {
    umbrella header "SDL3/SDL.h"
    link "SDL3"
    export *
}

And I have created a system library for SDL3 itself as well as a Swift target that depends on it that I intend to fill with SDL wrappers

// swift-tools-version:6.1
import PackageDescription

let package = Package(
    name: "SwfitDL",
    products: [
        .library(name: "SwiftDL", targets: ["SwiftDL"])
    ],
    targets: [
        .systemLibrary(name: "CSDL3", path: "Dependencies/SDL3", pkgConfig: nil, providers: []),
        .target(
            name: "SwiftDL", dependencies: ["CSDL3"],
            linkerSettings: [
                .unsafeFlags(["-L", "./Dependencies/SDL3"]),
                .unsafeFlags(["-I", "./Dependencies/SDL3"]),
                .linkedLibrary("SDL3"),
            ]
        ),
    ]
)

But for the life of me I cannot get it to build. Instead I get the same error:

 error: 'SDL3/SDL_stdinc.h' file not found
32 | #define SDL_h_
33 |
34 | #include <SDL3/SDL_stdinc.h>
   |          `- error: 'SDL3/SDL_stdinc.h' file not found

I have checked, that file is located in the SDL3 folder with all the other headers. All the other examples I have found online don't support Windows or they expect SDL3 to be available on the system path which also isn't the case here. Any help would be hugely appreciated

2

I've started a similar project a few years ago. I used this for Windows:

.unsafeFlags(["-Isdl-windows/include"]) // for swiftSettings
.unsafeFlags(["-Lsdl-windows/lib"]) // for linkerSettings

But I haven't worked on this code for a while, so I'm not sure it still works.

3

Thanks for the suggestion, but pretty certain that's the same as what I have done here just with different folder names. I tried nonetheless and get the exact same result

4

No, the linkerSettings are only applied at link time. The include path actually needs to be in swiftSettings so that it gets passed to the compiler.

5

or cSettings if you have C code or cxxSettings for C++.

6

Thanks, I updated my Package.swift file to look like this:

// swift-tools-version:6.1
import PackageDescription

let package: Package = Package(
    name: "SwfitDL",
    products: [
        .library(name: "SwiftDL", targets: ["SwiftDL"])
    ],
    targets: [
        .systemLibrary(
            name: "CSDL3",
            path: "Dependencies/SDL3",
            pkgConfig: nil,
            providers: []
        ),
        .target(
            name: "CSDL",
            dependencies: [.target(name: "CSDL3")],
            path: "Dependencies/SDL3",
            cSettings: [
                .headerSearchPath("Dependencies/SDL3/include")
            ],
            linkerSettings: [
                .unsafeFlags(["-L", "Dependencies/SDL3/lib"]),
                .linkedLibrary("SDL3"),
            ]
        ),
        .target(
            name: "SwiftDL",
            dependencies: ["CSDL"],
        ),
    ]
)

And that has fixed my unable to find header issues. Now I just have build issues relating to one of the headers being included multiple times which I have a feeling is going to be a unique issue between SDL3 and Swift and not something that is going to be easily debugged