# Issue using Swift macros in SwiftPM package when targeting Wasm

**URL:** <https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363>\
**Category:** Using Swift\
**Tags:** wasm, macros\
**Created:** [April 20, 2024, 7:36am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363 "2024-04-20T07:36:48Z")\
**Posts on this page:** 19\
**Page:** 1

<div class="post-metadata">

**Author:** ![stackotter](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/stackotter/32/20670_2.png) [@stackotter](https://forums.swift.org/u/stackotter)\
**Post date:** [April 20, 2024, 7:36am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/1 "2024-04-20T07:36:48Z")

</div>

## Tl;dr

I'm failing to compile a SwiftPM package for WASM due to the package's use of macros. Is this expected behaviour? And is there a known workaround?

Cheers!

## Context

I'm writing an interpreter for a custom programming language ([galah](https://github.com/stackotter/galah)) and I'm attempting to build the interpreter for WASM so that I can make an online playground for people to try out the language (not much to see yet, the language is still pretty simple and very constrained).

In the interpreter's code I've used macros to express a pattern that I couldn't otherwise (the details aren't important).

## The issue

I have attempted to build the interpreter for WASM with both of the following commands,

```sh
/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2024-04-04-a.xctoolchain/usr/bin/swift build --experimental-swift-sdk 5.10-SNAPSHOT-2024-04-09-a-wasm --target GalahInterpreter

/Users/stackotter/Library/Developer/Toolchains/swift-wasm-5.9.2-RELEASE.xctoolchain/usr/bin/swift build --triple wasm32-unknown-wasi --target GalahInterpreter

```

In both cases I get the follow errors,

```txt
/Users/stackotter/Desktop/Projects/LangDev/galah/.build/checkouts/swift-syntax/Sources/SwiftCompilerPlugin/CompilerPlugin.swift:103:19: error: cannot find 'dup' in scope
    let inputFD = dup(fileno(stdin))
                  ^~~
/Users/stackotter/Desktop/Projects/LangDev/galah/.build/checkouts/swift-syntax/Sources/SwiftCompilerPlugin/CompilerPlugin.swift:117:20: error: cannot find 'dup' in scope
    let outputFD = dup(fileno(stdout))
                   ^~~
/Users/stackotter/Desktop/Projects/LangDev/galah/.build/checkouts/swift-syntax/Sources/SwiftCompilerPlugin/CompilerPlugin.swift:124:11: error: cannot find 'dup2' in scope
    guard dup2(fileno(stderr), fileno(stdout)) >= 0 else {
          ^~~~

```

I have run the commands with `-v` and found that SwiftPM is building `SwiftCompilerPlugin` for WASM even though it's only getting used by macro (which afaik gets compiled for the host platform, so compiling `SwiftCompilerPlugin` for WASM is completely unnecessary work, and incorrect if incorporated into the macro).

## Package setup

```swift
// swift-tools-version: 5.9

import CompilerPluginSupport
import PackageDescription

let package = Package(
    name: "galah",
    platforms: [.macOS(.v10_15)],
    products: [
        .library(
            name: "GalahInterpreter",
            targets: ["GalahInterpreter"]
        )
    ],
    dependencies: [
        .package(url: "https://github.com/apple/swift-argument-parser", from: "1.3.0"),
        .package(
            url: "https://github.com/apple/swift-syntax.git",
            from: "509.0.0"
        ),
        .package(
            url: "https://github.com/stackotter/swift-macro-toolkit",
            from: "0.3.1"
        ),
    ],
    targets: [
        .executableTarget(
            name: "galah",
            dependencies: [
                "GalahInterpreter",
                .product(name: "ArgumentParser", package: "swift-argument-parser"),
            ]
        ),
        .target(
            name: "GalahInterpreter",
            dependencies: [
                "UtilityMacros"
            ]
        ),

        .macro(
            name: "UtilityMacrosPlugin",
            dependencies: [
                .product(name: "SwiftSyntax", package: "swift-syntax"),
                .product(name: "SwiftSyntaxMacros", package: "swift-syntax"),
                .product(name: "SwiftCompilerPlugin", package: "swift-syntax"),
                .product(name: "MacroToolkit", package: "swift-macro-toolkit"),
            ]
        ),
        .target(name: "UtilityMacros", dependencies: ["UtilityMacrosPlugin"]),

        .testTarget(
            name: "GalahInterpreterTests",
            dependencies: ["GalahInterpreter"]
        ),
    ]
)

```

## Troubleshooting

I tried splitting the macros into a separate (local) package (to remove the direct swift-syntax dependency from `galah`), but got the exact same errors again.

---

<div class="post-metadata">

**Author:** ![kateinoigakukun](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/kateinoigakukun/32/16706_2.png) [@kateinoigakukun](https://forums.swift.org/u/kateinoigakukun)\
**Post date:** [April 20, 2024, 7:55am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/2 "2024-04-20T07:55:56Z")

</div>

SwiftPM does not support Macro with cross-compilation context in the stable toolchains yet.  
But the support has been landed quite recently, so the next nightly toolchain will unlock the limitation hopefully. [Revert "Revert "Support macros when cross-compiling (#7118)" (#7352)" by MaxDesiatov · Pull Request #7353 · apple/swift-package-manager · GitHub](https://github.com/apple/swift-package-manager/pull/7353)

---

<div class="post-metadata">

**Author:** ![stackotter](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/stackotter/32/20670_2.png) [@stackotter](https://forums.swift.org/u/stackotter)\
**Post date:** [April 20, 2024, 8:04am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/3 "2024-04-20T08:04:49Z")

</div>

Amazing, thanks! Had a feeling it might be something WIP that I hadn't heard about.

I'll try building `main` branch SwiftPM for myself and try it out before the next toolchain.

---

<div class="post-metadata">

**Author:** ![stackotter](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/stackotter/32/20670_2.png) [@stackotter](https://forums.swift.org/u/stackotter)\
**Post date:** [April 21, 2024, 11:47am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/4 "2024-04-21T11:47:25Z")

</div>

![Screenshot 2024-04-21 at 4.55.11 pm](https://global.discourse-cdn.com/swift/original/3X/3/b/3b9db6b4ac5bb5fe3c4827e00b4b875cc8f15582.png)

Thanks for the help! After resolving a few other issues that I ran into with JavaScriptKit and stuff, I finally managed to get [an online playground](https://stackotter.github.io/galah/) working 🎉

* * *

I faced a few different issues while trying to get this working, if any of these aren't already known I'd be happy to split them out into separate topics or GitHub issues.

## Hiccups

My first working wasm example was a simple `print("Hello, world!")` which I got working one I built SwiftPM from the `main` branch. When I then tried to add the JavaScriptKit dependency the runtime let me know that JavaScriptKit requires the reactor ABI, which I promptly built my example with.

Whenever I loaded this latest build (with the reactor ABI) in the browser nothing would happen, even if I included `(Int?.none)!` to force a fatal error nothing happened. After quite a bit of digging I eventually discovered that JavaScriptKit looks for an exported `main` function to call which my built wasm didn't have. I ended up solving the issue by adding `["-Xlinker", "--export=main"]` to the target's `linkerSettings` in my package manifest.

Is that meant to be required or might it be something strange about my Swift toolchain? If it's meant to be required as a workaround, it'd be great if that could be added to the docs.

## Up-to-date SwiftWASM examples

When trying to resolve my issues I was trying to find example projects to see if I was doing anything differently, but all of the projects that I found hadn't been touched in a few years and either relied on old versions of carton and JavaScriptKit or wouldn't compile. Are there any up-to-date SwiftWASM examples that I missed? If not, I might try updating an existing one for future reference (happy to update whichever example is decided to be the most 'official').

---

<div class="post-metadata">

**Author:** ![kateinoigakukun](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/kateinoigakukun/32/16706_2.png) [@kateinoigakukun](https://forums.swift.org/u/kateinoigakukun)\
**Post date:** [April 21, 2024, 1:41pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/5 "2024-04-21T13:41:12Z")

</div>

Awesome! Thanks for sharing 🙂

> [@stackotter](#):
>
> Is that meant to be required or might it be something strange about my Swift toolchain? If it's meant to be required as a workaround, it'd be great if that could be added to the docs.

Yes, it's a quirk of WASI reactor ABI and Swift. The workaround would be automatically applied when building with [carton](https://github.com/swiftwasm/carton), but if you directly use `swift build`, you need to apply them by yourself.

Anyway, that should be documented somewhere. Which documentation did you refer to when troubleshooting? [book.swiftwasm.org](http://book.swiftwasm.org)?

> [@stackotter](#):
>
> Are there any up-to-date SwiftWASM examples that I missed?

I have not updated public examples for a while, so your playground is the latest working example 😅

---

<div class="post-metadata">

**Author:** ![stackotter](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/stackotter/32/20670_2.png) [@stackotter](https://forums.swift.org/u/stackotter)\
**Post date:** [April 22, 2024, 3:44am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/6 "2024-04-22T03:44:19Z")

</div>

> [@kateinoigakukun](#):
>
> The workaround would be automatically applied when building with [carton](https://github.com/swiftwasm/carton), but if you directly use `swift build`, you need to apply them by yourself.

Yeah, I figured carton might do that automatically. I couldn't get carton working with my build of SwiftPM's main branch (likely due to having main-branch SwiftPM but stable 5.9.2 swiftc?). SwiftPM was expecting an `echoLogs` key in the output from the plugin but wasn't getting it. The issue was also happening when using plain old `swift build` from my Xcode toolchain (which also has the issue of having swiftpm 5.9.0 and swiftc 5.9.2 for some weird reason).

Anyway, yeah I think having good instructions for doing things manually would be great. I think it's always important for people to be able to understand what's going on under-the-hood so that if something goes wrong they can work around it.

It could be useful to have a simple repository somewhere basically containing the JS files that I've got in [galah's static directory](https://github.com/stackotter/galah/tree/b1e28a95a4af5a94da8a5762f62260e300b0d91a/static) so that people can just drop in their own `main.wasm` or `main.wasm.gz` to get things working manually without having to figure out how to transfile the Swift Wasm runtime typescript files from carton or the JavaScriptKit resources from JavaScriptKit. `carton` would still be recommended, but having this manual alternative would make it easier for other tools to also implement Swift Wasm support.

Alternatively, `carton` could document how to build the typescript files in `entrypoint` and how to use them manually (which took me a while to figure out, I had to dig through the code to find the commands used to build the typescript files).

Also, is the Swift Wasm runtime (the `swjs` set of functions) only contained in Carton? Or is there a non-Carton way to easily integrate the JS-side runtime into other build systems if someone is using React/Svelte etc?

> [@kateinoigakukun](#):
>
> Which documentation did you refer to when troubleshooting? [book.swiftwasm.org](http://book.swiftwasm.org)?

Yeah, I think that's the only real documentation that I found.

> [@kateinoigakukun](#):
>
> I have not updated public examples for a while, so your playground is the latest working example 😅

Hahah ok 😅

---

<div class="post-metadata">

**Author:** ![MikeIsaev](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/mikeisaev/32/3446_2.png) [@MikeIsaev](https://forums.swift.org/u/MikeIsaev)\
**Post date:** [May 7, 2024, 4:14pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/7 "2024-05-07T16:14:05Z")

</div>

Having same errors on the latest 5.10 snapshots

```swift
.build/checkouts/swift-syntax/Sources/SwiftCompilerPlugin/CompilerPlugin.swift:103:19: error: cannot find 'dup' in scope
    let inputFD = dup(fileno(stdin))
                  ^~~.build/checkouts/swift-syntax/Sources/SwiftCompilerPlugin/CompilerPlugin.swift:117:20: error: cannot find 'dup' in scope
    let outputFD = dup(fileno(stdout))
                   ^~~.build/checkouts/swift-syntax/Sources/SwiftCompilerPlugin/CompilerPlugin.swift:124:11: error: cannot find 'dup2' in scope
    guard dup2(fileno(stderr), fileno(stdout)) >= 0 else {
          ^~~~

```

[stackotter](https://forums.swift.org/u/stackotter) have you had a chance to cross-compile into wasi any project with macros successfully?

---

<div class="post-metadata">

**Author:** ![Max\_Desiatov](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/max_desiatov/32/20654_2.png) [@Max\_Desiatov](https://forums.swift.org/u/Max_Desiatov)\
**Post date:** [May 7, 2024, 4:24pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/8 "2024-05-07T16:24:56Z")

</div>

Cross-compilation for macros is only supported in latest development snapshots of Swift. I won't be cherry-picked to 5.10 and may be cherry-picked to 6.0 only if it becomes stable soon enough.

---

<div class="post-metadata">

**Author:** ![MikeIsaev](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/mikeisaev/32/3446_2.png) [@MikeIsaev](https://forums.swift.org/u/MikeIsaev)\
**Post date:** [May 7, 2024, 4:30pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/9 "2024-05-07T16:30:27Z")

</div>

On latest development snapshots and swift-6 snapshots I'm getting

```swift
.build/wasm32-unknown-wasi/debug/JavaScriptKit.build/DerivedSources/resource_bundle_accessor.swift:1:8: error: no such module 'Foundation'
 1 | import Foundation
   | `- error: no such module 'Foundation'
 2 |
 3 | extension Foundation.Bundle {

```

unfortunately.

> [@Max\_Desiatov](#):
>
> I won't be cherry-picked to 5.10 and may be cherry-picked to 6.0 only if it becomes stable soon enough.

It means that macros is not available for swift-wasm for now, right?

Would be so nice to start using macros for swift-wasm projects

---

<div class="post-metadata">

**Author:** ![Max\_Desiatov](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/max_desiatov/32/20654_2.png) [@Max\_Desiatov](https://forums.swift.org/u/Max_Desiatov)\
**Post date:** [May 7, 2024, 4:32pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/10 "2024-05-07T16:32:04Z")

</div>

> [@MikeIsaev](#):
>
> It means that macros is not available for swift-wasm for now, right?

It is available in development snapshots off `main` only, but not available in 5.10 and 6.0 snapshots.

---

<div class="post-metadata">

**Author:** ![MikeIsaev](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/mikeisaev/32/3446_2.png) [@MikeIsaev](https://forums.swift.org/u/MikeIsaev)\
**Post date:** [May 7, 2024, 4:37pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/11 "2024-05-07T16:37:27Z")

</div>

Sorry for the dumb question

 ![Screenshot 2024-05-07 at 20.33.15](https://global.discourse-cdn.com/swift/original/3X/6/2/62228393b06ad4e90240383c1c2df82461cc07fe.png)

Is it development snapshot of `main` where fix is available?

I tried `swift-wasm-DEVELOPMENT-SNAPSHOT-2024-05-02-a` and getting

```swift
no such module 'Foundation'

```

[Max\_Desiatov](https://forums.swift.org/u/Max_Desiatov) could you please point me to the right direction where to get the correct snapshot, I would love to try it 🙏

---

<div class="post-metadata">

**Author:** ![Max\_Desiatov](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/max_desiatov/32/20654_2.png) [@Max\_Desiatov](https://forums.swift.org/u/Max_Desiatov)\
**Post date:** [May 7, 2024, 6:05pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/12 "2024-05-07T18:05:31Z")

</div>

> [@MikeIsaev](#):
>
> Is it development snapshot of `main` where fix is available?
> 
> I tried `swift-wasm-DEVELOPMENT-SNAPSHOT-2024-05-02-a`

Yes, that's the correct snapshot that contains the fix for cross-compilation with macros.

> [@MikeIsaev](#):
>
> and getting
> 
> ```swift
> no such module 'Foundation'
> 
> ```

I'm not sure what's up with that, could be an issue with the SwiftWasm distribution. Or a bug with SwiftPM resources if you're seeing it with JavaScriptKit exclusively but don't use Foundation in your packages.

@kateinoigakukun have you seen this error before by any chance?

---

<div class="post-metadata">

**Author:** ![kateinoigakukun](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/kateinoigakukun/32/16706_2.png) [@kateinoigakukun](https://forums.swift.org/u/kateinoigakukun)\
**Post date:** [May 7, 2024, 6:31pm UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/13 "2024-05-07T18:31:21Z")

</div>

It's hard to diagnose without commands you invoke, but I guess you are using toolchain distribution (not Swift SDK), right? In that case could you try adding `--static-swift-stdlib` to your `swift build` command arguments?

---

<div class="post-metadata">

**Author:** ![MikeIsaev](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/mikeisaev/32/3446_2.png) [@MikeIsaev](https://forums.swift.org/u/MikeIsaev)\
**Post date:** [May 8, 2024, 2:04am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/14 "2024-05-08T02:04:33Z")

</div>

I'm trying to execute `swift build` with the following arguments

```swift
/Users/imike/Library/Developer/Toolchains/swift-wasm-DEVELOPMENT-SNAPSHOT-2024-05-02-a.xctoolchain/usr/bin/swift build 
    -c debug
    --triple wasm32-unknown-wasi
    -Xswiftc -Xclang-linker
    -Xswiftc -mexec-model=reactor
    -Xlinker -lCoreFoundation
    -Xlinker -licuuc
    -Xlinker -licui18n
    -Xlinker --export=main

```

adding `--static-swift-stdlib` seems removes

```swift
no such module 'Foundation'

```

error, but build still fails with

```swift
error: link command failed with exit code 1 (use -v to see invocation)
clang: error: linker command failed with exit code 1 (use -v to see invocation)

```

btw I'm executing `rm -rf .build` before each build

@kateinoigakukun could you please suggest the right command arguments?

---

<div class="post-metadata">

**Author:** ![MikeIsaev](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/mikeisaev/32/3446_2.png) [@MikeIsaev](https://forums.swift.org/u/MikeIsaev)\
**Post date:** [May 8, 2024, 4:30am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/15 "2024-05-08T04:30:56Z")

</div>

I prepared two clean projects to reproduce the problem

1. [**nonmacro** project source code](https://drive.google.com/file/d/1upZR8gphPZ5LZmI7N0eGIEgUdo3cGI82/view?usp=share_link)
2. [**macro** project source code](https://drive.google.com/file/d/1kakcLQ0QLi5cX-oBcN-Ps2axyfW84kVO/view?usp=share_link)

Command that I use to build these projects

```swift
/Users/imike/Library/Developer/Toolchains/swift-wasm-DEVELOPMENT-SNAPSHOT-2024-05-02-a.xctoolchain/usr/bin/swift build
    -c debug
    --static-swift-stdlib
    --triple wasm32-unknown-wasi
    -Xswiftc -Xclang-linker
    -Xswiftc -mexec-model=reactor
    -Xlinker -lCoreFoundation
    -Xlinker -licuuc
    -Xlinker -licui18n
    -Xlinker --export-if-defined=__main_argc_argv

```

**nonmacro** project builds with no issues

**macro** project fails:

```swift
Fetching https://github.com/apple/swift-syntax.git from cache
Fetching https://github.com/swiftwasm/JavaScriptKit from cache
Fetched https://github.com/swiftwasm/JavaScriptKit from cache (0.90s)
Fetched https://github.com/apple/swift-syntax.git from cache (0.94s)
Computing version for https://github.com/apple/swift-syntax.git
Computed https://github.com/apple/swift-syntax.git at 510.0.2 (0.04s)
Computing version for https://github.com/swiftwasm/JavaScriptKit
Computed https://github.com/swiftwasm/JavaScriptKit at 0.19.2 (0.03s)
Creating working copy for https://github.com/swiftwasm/JavaScriptKit
Working copy of https://github.com/swiftwasm/JavaScriptKit resolved at 0.19.2
Creating working copy for https://github.com/apple/swift-syntax.git
Working copy of https://github.com/apple/swift-syntax.git resolved at 510.0.2
Building for debugging...
warning: Could not read SDKSettings.json for SDK at: /Users/imike/Library/Developer/Toolchains/swift-wasm-DEVELOPMENT-SNAPSHOT-2024-05-02-a.xctoolchain/usr/share/wasi-sysroot
<unknown>:0: warning: libc not found for 'wasm32-unknown-wasi'; C stdlib may be unavailable
warning: Could not read SDKSettings.json for SDK at: /Users/imike/Library/Developer/Toolchains/swift-wasm-DEVELOPMENT-SNAPSHOT-2024-05-02-a.xctoolchain/usr/share/wasi-sysroot
<unknown>:0: warning: libc not found for 'wasm32-unknown-wasi'; C stdlib may be unavailable
<unknown>:0: warning: libc not found for 'wasm32-unknown-wasi'; C stdlib may be unavailable
<unknown>:0: warning: libc not found for 'wasm32-unknown-wasi'; C stdlib may be unavailable
error: link command failed with exit code 1 (use -v to see invocation)
ld: unknown options: --export-if-defined=__main_argc_argv
clang: error: linker command failed with exit code 1 (use -v to see invocation)
[256/261] Linking MyMacroMacros-tool

```

The snapshot that I'm using is **swift-wasm-DEVELOPMENT-SNAPSHOT-2024-05-02-a**

@kateinoigakukun could you please take a look 🙏

---

<div class="post-metadata">

**Author:** ![kateinoigakukun](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/kateinoigakukun/32/16706_2.png) [@kateinoigakukun](https://forums.swift.org/u/kateinoigakukun)\
**Post date:** [May 8, 2024, 7:09am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/16 "2024-05-08T07:09:19Z")

</div>

Interesting. The linker options provided through `-Xlinker` cannot be used to link macro executables. So you need to specify them at target scope in Package.swift.

```swift
        .executableTarget(
            name: "SWasm6App",
            dependencies: [
                "MyMacro",
                .product(name: "JavaScriptKit", package: "JavaScriptKit"),
                .product(name: "JavaScriptBigIntSupport", package: "JavaScriptKit"),
            ],
            linkerSettings: [
                .unsafeFlags(["-Xclang-linker", "-mexec-model=reactor", "-Xlinker", "--export-if-defined=__main_argc_argv"]),
            ]
        ),

```

---

<div class="post-metadata">

**Author:** ![MikeIsaev](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/mikeisaev/32/3446_2.png) [@MikeIsaev](https://forums.swift.org/u/MikeIsaev)\
**Post date:** [May 8, 2024, 8:03am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/17 "2024-05-08T08:03:48Z")

</div>

Thank you @kateinoigakukun this way it works! 🥳 But it's a bug, right? Since I use different linker options in different situations I can't hardcode them into `Package.swift`...

Though `unsafeFlags` condition `.when(platforms: [.wasi])` solves it for now

---

<div class="post-metadata">

**Author:** ![kateinoigakukun](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/kateinoigakukun/32/16706_2.png) [@kateinoigakukun](https://forums.swift.org/u/kateinoigakukun)\
**Post date:** [May 8, 2024, 8:11am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/18 "2024-05-08T08:11:33Z")

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We don't have a way to specify different options for building build-time tools and target executables at this moment, so it might be a missing piece of SwiftPM.

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<div class="post-metadata">

**Author:** ![stackotter](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/stackotter/32/20670_2.png) [@stackotter](https://forums.swift.org/u/stackotter)\
**Post date:** [May 9, 2024, 5:17am UTC](https://forums.swift.org/t/issue-using-swift-macros-in-swiftpm-package-when-targeting-wasm/71363/19 "2024-05-09T05:17:25Z")

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> [@MikeIsaev](#):
>
> [stackotter](https://forums.swift.org/u/stackotter) have you had a chance to cross-compile into wasi any project with macros successfully?

I see you've got yours working now too, but yes I have! My Galah programming language has an [online interpreter](https://stackotter.github.io/galah/) which runs in the browser using Swift Wasm. Currently facing issues with variadic generics but macros are working fine.