glibc warnings compiling for 5.9-RELEASE_ubuntu_jammy_aarch64

[rvsrvs]

I've created a simple helloworld tool, and compiling it generates warning messages that seem to be spurious. Here's the project structure:

./Package.swift
./Sources/helloworld/main.swift
./Tests/LinuxMain.swift
./Tests/helloworldTests/helloworldTests.swift
./Tests/helloworldTests/XCTestManifests.swift

Package consists of:

// swift-tools-version:5.9
import PackageDescription

let package = Package(
    name: "helloworld",
    dependencies: [],
    targets: [
        .executableTarget(
            name: "helloworld",
            dependencies: []
        ),
        .testTarget(
            name: "helloworldTests",
            dependencies: ["helloworld"]
        ),
    ]
)

main.swift consists of:

print("Successful launch!")

This produces the following output:

swift build --experimental-swift-sdk 5.9-RELEASE_ubuntu_jammy_aarch64
Building for debugging...
warning: Could not read SDKSettings.json for SDK at: /Users/rvs/Library/org.swift.swiftpm/swift-sdks/5.9-RELEASE_ubuntu_jammy_aarch64.artifactbundle/5.9-RELEASE_ubuntu_jammy_aarch64/aarch64-unknown-linux-gnu/ubuntu-jammy.sdk
<unknown>:0: warning: glibc not found for 'aarch64-unknown-linux-gnu'; C stdlib may be unavailable
<unknown>:0: warning: glibc not found for 'aarch64-unknown-linux-gnu'; C stdlib may be unavailable
warning: Could not read SDKSettings.json for SDK at: /Users/rvs/Library/org.swift.swiftpm/swift-sdks/5.9-RELEASE_ubuntu_jammy_aarch64.artifactbundle/5.9-RELEASE_ubuntu_jammy_aarch64/aarch64-unknown-linux-gnu/ubuntu-jammy.sdk
[5/5] Linking helloworld
Build complete! (9.02s)

The glibc warnings seem to be spurious.

[Diggory]

Did you mean main.c or was that a typo?

[rvsrvs]

sorry main.swift. will fix

[MaxDesiatov]

Also tracked as rdar://115492638

[fwcd]

I've been having similar issues with my manually configured cross-compilation build where

swift build --sdk <path/to/sysroot>

no longer works as expected in 5.9. Swift neither seems to find libc nor any other libraries in the sysroot. For a full log, see e.g. this failed build (I prepare a sysroot in the first Docker stage, then copy it over into /usr/local/<targetarch>-ubuntu-jammy and point --sdk to this sysroot, along with some flags for the C/C++ compilers).

Would of course be nice to migrate over to the new SDK bundles once the Ubuntu host -> Ubuntu target scenario is properly supported, but I assume this is still a regression.

[rvsrvs]

This has gotten much worse in 5.9.1, now I get a ton of the following warnings:

clang-13: warning: -Z-reserved-lib-stdc++: 'linker' input unused [-Wunused-command-line-argument]
warning: Could not read SDKSettings.json for SDK at: /Users/____/Library/org.swift.swiftpm/swift-sdks/5.9.1-RELEASE_ubuntu_jammy_x86_64.artifactbundle/5.9.1-RELEASE_ubuntu_jammy_x86_64/x86_64-unknown-linux-gnu/ubuntu-jammy.sdk
<unknown>:0: warning: glibc not found for 'x86_64-unknown-linux-gnu'; C stdlib may be unavailable

The good news is that then after dozens of each of the above, I get:

[798/798] Linking echoserver
Build complete! (19.56s)