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Embedded: pass -nostdlib for Embedded Wasm #1534

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Embedded: pass -nostdlib for Embedded Wasm #1534

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ff2ac8b
Embedded: don't link `swiftrt.o` for bare metal
MaxDesiatov Jan 29, 2024
a37cf28
Embedded: pass `-nostdlib` for Embedded Wasm
MaxDesiatov Jan 29, 2024
2dce9db
Merge branch 'main' into maxd/embedded-no-stdlib
MaxDesiatov Jan 29, 2024
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5 changes: 5 additions & 0 deletions Sources/SwiftDriver/Jobs/GenericUnixToolchain+LinkerSupport.swift
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I guess the correct file you intended to modify is Sources/SwiftDriver/Jobs/WebAssemblyToolchain+LinkerSupport.swift. GenericUnixToolchain is not used for wasm targets.

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WebAssemblyToolchain is not used for Embedded Swift targets either, it's currently only picked up for WASI. I'm inclined to rename that one to WASIToolchain maybe?

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Sorry I was wrong. A bit off-topic, but I think we might need to use WebAssemblyToolchain for all platforms using wasm-ld including Embedded WebAssembly targets because wasm-ld has quite different options set than other unix linkers. (e.g. wasm-ld doesn't have --start-group, all wasm targets needs --global-base, etc)

Original file line number Diff line number Diff line change
Expand Up @@ -195,6 +195,11 @@ extension GenericUnixToolchain {
commandLine.appendPath(swiftrtPath)
}

// Embedded Wasm binaries don't have compatible compiler-rt or C stdlib available, turn it off by default.
if isEmbeddedEnabled && (targetTriple.arch == .wasm32 || targetTriple.arch == .wasm64) {
commandLine.appendFlag("-nostdlib")
}

// If we are linking statically, we need to add all
// dependencies to a library search group to resolve
// potential circular dependencies
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2 changes: 2 additions & 0 deletions Tests/SwiftDriverTests/SwiftDriverTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -6564,6 +6564,7 @@ final class SwiftDriverTests: XCTestCase {
XCTAssertFalse(linkJob.commandLine.contains(.flag("-force_load")))
XCTAssertFalse(linkJob.commandLine.contains(.flag("-rpath")))
XCTAssertFalse(linkJob.commandLine.contains(.flag("-lswiftCore")))
XCTAssertTrue(linkJob.commandLine.contains(.flag("-nostdlib")))
}

// Embedded Wasm link job
Expand All @@ -6576,6 +6577,7 @@ final class SwiftDriverTests: XCTestCase {
XCTAssertFalse(linkJob.commandLine.contains(.flag("-force_load")))
XCTAssertFalse(linkJob.commandLine.contains(.flag("-rpath")))
XCTAssertFalse(linkJob.commandLine.contains(.flag("-lswiftCore")))
XCTAssertTrue(linkJob.commandLine.contains(.flag("-nostdlib")))
XCTAssertFalse(linkJob.commandLine.joinedUnresolvedArguments.contains("swiftrt.o"))
}

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