Async function never returns in Swift 5.7 in release + static linking (Linux)

[PopFlamingo]

Describe the bug
I found a specific project setup where a simple call to a mostly empty async function never returns (note that this doesn't happen in simpler setups without some dependencies, see the linked repo for a reproducible issue).
Also, with some additional dependencies, even if not imported but just listed as dependencies in Package.swift, it can change the behavior and cause a crash with a segfault for instance.

Here, swift run -c release -Xswiftc -static-executable never goes beyond printing "During foo()"

func foo() async {
    print("During foo()")
}

@main
struct App {
    static func main() async throws {
        print("Before calling foo()")
        let bar = await foo()
        print("After calling foo()")
    }
}

Steps To Reproduce
Steps to reproduce the behavior:

1. Clone https://github.com/PopFlamingo/fluffy-disco.git
2. Run it with swift run -c release -Xswiftc -static-executable (I can reproduce from the swiftlang/swift:nightly-5.7-focal Docker image which currently has the following toolchain Swift version 5.7-dev (LLVM c94b55955148b74, Swift 13b3ac91a618617))

Note that the linked repo has a .devcontainer included for easier reproduction in VSCode and others.

Expected behavior
Program should print and exit but does not and stops in the foo() call.

Environment (please fill out the following information)

swift --version
Swift version 5.7-dev (LLVM c94b55955148b74, Swift 13b3ac91a618617)
Target: x86_64-unknown-linux-gnu

cc @ktoso

[PopFlamingo]

I didn't test it on macOS toolchains

[ktoso]

Extra note: it does work without the static linking option.

[ktoso]

More similar hangs reported over in apple/swift-distributed-actors#1004 in same Linux/docker environment (even without static linking).

[PopFlamingo]

I tried it again with the swift-5.7-DEVELOPMENT-SNAPSHOT-2022-08-02-a snapshot, there are also some warnings during the build (tested on Docker/Linux):

clang-13: warning: argument unused during compilation: '-pie' [-Wunused-command-line-argument]
/usr/lib/swift_static/linux/libFoundation.a(CFPlatform.c.o):CFPlatform.c:function CFCopyUserName: warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFPlatform.c.o):CFPlatform.c:function CFCopyUserName: warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFPlatform.c.o):CFPlatform.c:function CFCopyFullUserName: warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFPlatform.c.o):CFPlatform.c:function CFCopyFullUserName: warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFPlatform.c.o):CFPlatform.c:function _CFCopyHomeDirURLForUser: warning: Using 'getpwnam' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFPlatform.c.o):CFPlatform.c:function _CFCopyHomeDirURLForUser: warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFBundle_Main.c.o):CFBundle_Main.c:function CFBundleGetMainBundle: warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(FileManager.swift.o):FileManager.swift.o:function $s10Foundation11FileManagerC17_attributesOfItem6atPath26includingPrivateAttributesSDyAA0B12AttributeKeyVypGSS_SbtKF: warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(FileManager.swift.o):FileManager.swift.o:function $s10Foundation11FileManagerC17_attributesOfItem6atPath26includingPrivateAttributesSDyAA0B12AttributeKeyVypGSS_SbtKF: warning: Using 'getgrgid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFBundle_Binary.c.o):CFBundle_Binary.c:function _CFBundleDlfcnCheckLoaded: warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFBundle_Binary.c.o):CFBundle_Binary.c:function _CFBundleDlfcnLoadBundle: warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(CFBundle_Binary.c.o):CFBundle_Binary.c:function _CFBundleDlfcnLoadFramework: warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/swift_static/linux/libFoundation.a(Host.swift.o):Host.swift.o:function $s10Foundation4HostC8_resolveyyF: warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
[12/12] Linking Run

[ktoso]

I believe this wasn't an actual issue, since in the other bug @PopFlamingo confirmed that it was a logging issue instead:

It turns out this specific issue was actually logging related. Since I am not getting the logs directly from a shell, stdout needed to be flushed as Swift doesn't automatically do so after a print.
Thanks for your help! I will close this now.

[PopFlamingo]

@ktoso I checked again and this is still an actual issue. I tested it for the first time on macOS Docker today and I get the same hang as on Linux Docker.