Fails to compile on Fedora 39 with Swift 5.8.1 (From repos) or official 5.9 binaries

[JCWasmx86]

Expected behavior

It compiles on Arch Linux and Fedora 39 (Works on Fedora 38)

Actual behavior

Does not compile on Arch Linux/Fedora 39 (The following part of the issue assumes Fedora 39)

Steps to reproduce

1. Create fedora 39 VM/container
2. Install swift using dnf or use the official binaries from swift.org
3. Try to compile swift-log (From master or the latest release)

If possible, minimal yet complete reproducer code (or URL to code)

git clone https://github.com/apple/swift-log
cd swift-log
swift build
# Or
wget https://download.swift.org/swift-5.9-release/ubuntu2204/swift-5.9-RELEASE/swift-5.9-RELEASE-ubuntu22.04.tar.gz
tar xvf swift-5.9-RELEASE-ubuntu22.04.tar.gz
./swift-5.9-RELEASE-ubuntu22.04/usr/bin/swift build

/swift-log/Sources/Logging/Logging.swift:1392:64: error: value of optional type 'UnsafeMutablePointer<tm>?' must be unwrapped to a value of type 'UnsafeMutablePointer<tm>'
        strftime(&buffer, buffer.count, "%Y-%m-%dT%H:%M:%S%z", localTime)
                                                               ^
/swift-log/Sources/Logging/Logging.swift:1391:13: note: short-circuit using 'guard' to exit this function early if the optional value contains 'nil'
        let localTime = localtime(&timestamp)
            ^
        guard                                 else { return <#default value#> }
/swift-log/Sources/Logging/Logging.swift:1391:25: note: coalesce using '??' to provide a default when the optional value contains 'nil'
        let localTime = localtime(&timestamp)
                        ^
                                              ?? <#default value#>
/swift-log/Sources/Logging/Logging.swift:1391:25: note: force-unwrap using '!' to abort execution if the optional value contains 'nil'
        let localTime = localtime(&timestamp)
                        ^
                                             !
/swift-log/Sources/Logging/Logging.swift:1392:64: note: coalesce using '??' to provide a default when the optional value contains 'nil'
        strftime(&buffer, buffer.count, "%Y-%m-%dT%H:%M:%S%z", localTime)
                                                               ^
                                                                         ?? <#default value#>
/swift-log/Sources/Logging/Logging.swift:1392:64: note: force-unwrap using '!' to abort execution if the optional value contains 'nil'
        strftime(&buffer, buffer.count, "%Y-%m-%dT%H:%M:%S%z", localTime)
                                                               ^
                                                                        !
error: fatalError

SwiftLog version/commit hash

cb28750240a9389e0023ee3e3cb6c83ce0960f5c and 1.5.3

Swift & OS version (output of swift --version && uname -a)

Swift version 5.8.1 (swift-5.8.1-RELEASE)
Target: x86_64-unknown-linux-gnu
Linux 6d64617a9d4e 6.4.15-200.fc38.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Sep  7 00:25:01 UTC 2023 x86_64 GNU/Linux

and

Swift version 5.9 (swift-5.9-RELEASE)
Target: x86_64-unknown-linux-gnu
Linux 6d64617a9d4e 6.4.15-200.fc38.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Sep  7 00:25:01 UTC 2023 x86_64 GNU/Linux

I was able to fix this with the help of helje5 by doing this hack: https://github.com/JCWasmx86/swift-log/commit/332ed31d777c7acbf4790a790bcfb54fe264de27

[1Jo1]

I have the exact same issue on Arch Linux, maybe its a glibc related issue @JCWasmx86 thanks for this nice simple hack :)

glibc 2.38-5
Swift version 5.9 (swift-5.9-RELEASE)
Target: x86_64-unknown-linux-gnu`Swift version 5.9 (swift-5.9-RELEASE)
Target: x86_64-unknown-linux-gnu
6.5.5

[a40yostudent]

Looking at the same function called in the line 1392:

• on macOS Sonoma: `strftime(::::)

func strftime( : UnsafeMutablePointer!, : Int, : UnsafePointer!, : UnsafePointer! ) -> Int`

• on Ubuntu 23.10, using swift 5.9: `strftime(::::)

func strftime(_ s: UnsafeMutablePointer, _ _maxsize: Int, format: UnsafePointer, _ __tp: UnsafePointer) -> Int`

Looks like it is safe to just force unwrap localtime like this on line failing: strftime(&buffer, buffer.count, "%Y-%m-%dT%H:%M:%S%z", localTime!)

It worked on my computer™

[JCWasmx86]

But that would break code on Fedora 38 for example. Not sure what the best approach would be, as dropping somewhat recent OS versions like Fedora 38 is probably a bit too fast.

[a40yostudent]

Of course, I meant it's safe if you're on the OS experiencing this issue. I also wonder if the hack has been already tested on older versions.

[consuelita]

Also seeing this behavior on Ubuntu 23.10, Swift 5.9.1

[trufanov-nok]

Same problem Kubuntu 23.10, Swift 5.8.1/5.9.1

[lhoward]

Looks like this was fixed in f447991, but a new release would be handy.