Support swift build --experimental-xcframeworks-on-linux by vsarunas · Pull Request #1310 · swiftlang/swift-build

vsarunas · 2026-04-15T13:28:40Z

Allow use of --experimental-xcframeworks-on-linux flag as per #1250

These changes allows us to compile our code base on Linux using --build-system swiftbuild.

owenv

As I said in the linked issue, I don't think it makes sense to take this change - we shouldn't attempt to process malformed XCFrameworks that don't contain MachO binaries, and we should ensure the compiler is prepared to enforce the appropriate stability guarantees before allowing packages to vend binary shared libraries via artifact bundle on non-Apple platforms.

jakepetroules · 2026-04-21T18:48:12Z

    /// Given a platform and the variant, attempt to find an library within the XCFramework that can be used.
-    public func findLibrary(platform: String, platformVariant: String = "") -> XCFramework.Library? {
+    public func findLibrary(platform: String, platformVariant: String = "", architectures: [String] = []) -> XCFramework.Library? {
+        #if canImport(Darwin)


You can't use ifdefs here because this will not work for cross-compilation.

I think the actual condition here is whether the platform uses per-arch slices? You can extract the logic in the usesPerArchSlices property you added to LibraryKey and re-use that here.

OK! ifdef removed, originally I was trying to minimise the changes required and not thread through this argument.

jakepetroules · 2026-04-21T18:50:30Z

+        // that platform default archs to the host and allow a no-variant fallback.
+        let platformMatches = libraries.filter { $0.supportedPlatform == platform }
+        var effectiveArchs = architectures
+        if platform == "linux", effectiveArchs.isEmpty, let hostArch = Architecture.hostStringValue {


You can't use Architecture.hostStringValue here because this will not work for cross-compilation. architectures should never be an empty list - for the Linux case you can check that it contains exactly one value, and look up that value.

jakepetroules

Looking better! Commented on a few more small things...

jakepetroules · 2026-04-23T17:52:19Z

    @_spi(Testing) public static let mergeableMetadataVersion = Version(1, 1)

+    static func hasPerArchSlices(_ platform: String) -> Bool {
+        return platform == "linux"


Please change this to:

Suggested change

return platform == "linux"

return !["macosx", "iphoneos", "iphonesimulator", "appletvos", "appletvsimulator", "watchos", "watchsimulator", "xros", "xrsimulator", "driverkit"].contains(platform)

It's a bit verbose, but this is more correct and protects against edge cases if we end up splitting linux into multiple platforms, which @owenv and I have talked about doing to solve some cross compilation issues.

Adjusted, even more verbose as an existing test was failing.

jakepetroules · 2026-04-23T17:52:54Z

+                lib.supportedPlatform == platform && (lib.platformVariant ?? "") == platformVariant
+            }.first
+        }
+        // Linux ships per-arch XCFramework slices and typically omits SupportedPlatformVariant, so for


Suggested change

// Linux ships per-arch XCFramework slices and typically omits SupportedPlatformVariant, so for

// Non-Apple platforms ship per-arch XCFramework slices and typically omit SupportedPlatformVariant, so for

jakepetroules · 2026-04-23T17:53:21Z

+            }.first
+        }
+        // Linux ships per-arch XCFramework slices and typically omits SupportedPlatformVariant, so for
+        // that platform require exactly one target arch and allow a no-variant fallback.


Suggested change

// that platform require exactly one target arch and allow a no-variant fallback.

// those platforms, require exactly one target arch and allow a no-variant fallback.

jakepetroules · 2026-04-23T17:55:13Z

            // identifier is only used for tracking the offending library
            hasher.combine(platform)
            hasher.combine(platformVariant)
+            if usesPerArchSlices {


This needs to be unconditionally added to the hash; Hashable and Equatable conformances are not the right place for this sort of business logic.

Business logic moved to validate().

jakepetroules · 2026-04-23T17:55:27Z

+            guard lhs.platform == rhs.platform, lhs.platformVariant == rhs.platformVariant else {
+                return false
+            }
+            return lhs.usesPerArchSlices ? (lhs.architectures == rhs.architectures) : true


This needs to be unconditionally compared; Hashable and Equatable conformances are not the right place for this sort of business logic.

jakepetroules · 2026-04-23T17:56:59Z

+        // Linux ships per-arch XCFramework slices and typically omits SupportedPlatformVariant, so for
+        // that platform require exactly one target arch and allow a no-variant fallback.
+        guard architectures.count == 1 else { return nil }
+        let targetArch = architectures[0]


You can combine the .count==1 check with this:

Suggested change

let targetArch = architectures[0]

guard let targetArch = architectures.only else { return nil }

jakepetroules · 2026-04-24T22:11:02Z

+            return false
+        }
+        // SDK names from Info.plist.
+        let sdkCanonicalNames = [


Sorry, I forgot these platform names are in terms of the triples, not the Xcode platform names. You shouldn't check both -- just the BuildVersion.Platform code path is sufficient.

Simplified.

jakepetroules · 2026-04-25T21:55:22Z

@swift-ci test

vsarunas · 2026-04-26T16:06:55Z

Ubuntu failure https://github.com/swiftlang/swift-build/actions/runs/24925300005/job/73036104365?pr=1310#step:14:43080 doesn't seem to be related to the changes:

◇ Test case passing 1 argument buildSystem → .swiftbuild to enableDisableCache(buildSystem:) started.
**** FAILURE EXECUTING SUBPROCESS ****
output: 
stderr: 
*** Signal 11: Backtracing from 0x7f19595ce9aa... failed ***

*** Backtracer crashed during backtracing; attempting to backtrace backtracer: ***

*** Signal 4: Backtracing from 0x7f2082b4983c... done ***

*** Program crashed: Illegal instruction at 0x00007f2082b4983c ***

Platform: x86_64 Linux (Ubuntu 22.04.5 LTS)

Thread 0 "swift-backtrace" crashed:

 0                0x00007f2082b4983c specialized ImageSource.fetchSLEB128(from:) + 220 in libswiftRuntime.so
 1 [ra]           0x00007f2082afcce7 DwarfReader.read(form:at:addressSize:isDwarf64:unit:shouldFetchIndirect:constantValue:) + 1654 in libswiftRuntime.so
 2 [ra]           0x00007f2082afea5e DwarfReader.readDieAttributes(at:unit:abbrevInfo:shouldFetchIndirect:) + 365 in libswiftRuntime.so
 3 [ra]           0x00007f2082b04907 DwarfReader._scanUnits() + 646 in libswiftRuntime.so
 4 [ra]           0x00007f2082b0068f DwarfReader._lazyInfo.getter + 46 in libswiftRuntime.so
 5 [ra]           0x00007f2082b00b11 DwarfReader.lookupInlineCallSites(at:) + 32 in libswiftRuntime.so
 6 [ra]           0x00007f2082b0f501 ElfImage.inlineCallSites(at:) + 48 in libswiftRuntime.so

owenv

I guess this isn't doing too much harm

Support swift build --experimental-xcframeworks-on-linux

1802a7b

vsarunas requested review from aciidgh, jakepetroules, mhrawdon, neonichu and owenv as code owners April 15, 2026 13:28

vsarunas mentioned this pull request Apr 15, 2026

XCFramework: Unknown library type with extension 'so' in library 'linux-aarch64' #1250

Closed

owenv requested changes Apr 15, 2026

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jakepetroules requested changes Apr 21, 2026

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Remove ifdef

64bd510

vsarunas requested a review from jakepetroules April 22, 2026 11:30

jakepetroules requested changes Apr 23, 2026

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PR feedback

f42a5bc

vsarunas requested a review from jakepetroules April 24, 2026 13:39

rename

18dff13

vsarunas force-pushed the experimental-xcframeworks-on-linux branch from 3c2fee8 to 18dff13 Compare April 24, 2026 13:45

jakepetroules requested changes Apr 24, 2026

View reviewed changes

Simplify hasPerArchSlices

a262796

vsarunas requested a review from jakepetroules April 25, 2026 07:05

jakepetroules approved these changes Apr 25, 2026

View reviewed changes

vsarunas requested a review from owenv April 27, 2026 16:54

owenv approved these changes Apr 28, 2026

View reviewed changes

owenv merged commit 683439b into swiftlang:main Apr 28, 2026
121 of 126 checks passed

vsarunas mentioned this pull request Jun 16, 2026

Process the correct slice for multi-arch Linux XCFrameworks #1462

Open

	return platform == "linux"
	return !["macosx", "iphoneos", "iphonesimulator", "appletvos", "appletvsimulator", "watchos", "watchsimulator", "xros", "xrsimulator", "driverkit"].contains(platform)

	// Linux ships per-arch XCFramework slices and typically omits SupportedPlatformVariant, so for
	// Non-Apple platforms ship per-arch XCFramework slices and typically omit SupportedPlatformVariant, so for

	// that platform require exactly one target arch and allow a no-variant fallback.
	// those platforms, require exactly one target arch and allow a no-variant fallback.

	let targetArch = architectures[0]
	guard let targetArch = architectures.only else { return nil }

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vsarunas commented Apr 15, 2026

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jakepetroules commented Apr 25, 2026

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vsarunas commented Apr 26, 2026

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