Handle strerror_r return type of UnsafeMutablePointer<CChar> for Android

[marcprux]

This fixes the Android build error:

/opt/src/github/swift-everywhere/swift-tools-support-core/Sources/TSCBasic/misc.swift:331:24: error: binary operator '==' cannot be applied to operands of type 'UnsafeMutablePointer<CChar>' (aka 'UnsafeMutablePointer<Int8>') and 'Int32'
329 |                 var buf = [Int8](repeating: 0, count: cap)
330 |                 let err = TSCLibc.strerror_r(errno, &buf, buf.count)
331 |                 if err == EINVAL {
    |                        |- error: binary operator '==' cannot be applied to operands of type 'UnsafeMutablePointer<CChar>' (aka 'UnsafeMutablePointer<Int8>') and 'Int32'
    |                        `- note: overloads for '==' exist with these partially matching parameter lists: (Int32, Int32)
332 |                     return "Unknown error \(errno)"
333 |                 }

/opt/src/github/swift-everywhere/swift-tools-support-core/Sources/TSCBasic/misc.swift:334:24: error: binary operator '==' cannot be applied to operands of type 'UnsafeMutablePointer<CChar>' (aka 'UnsafeMutablePointer<Int8>') and 'Int32'
332 |                     return "Unknown error \(errno)"
333 |                 }
334 |                 if err == ERANGE {
    |                        |- error: binary operator '==' cannot be applied to operands of type 'UnsafeMutablePointer<CChar>' (aka 'UnsafeMutablePointer<Int8>') and 'Int32'
    |                        `- note: overloads for '==' exist with these partially matching parameter lists: (Int32, Int32)
335 |                     cap *= 2
336 |                     continue

/opt/src/github/swift-everywhere/swift-tools-support-core/Sources/TSCBasic/misc.swift:338:24: error: binary operator '!=' cannot be applied to operands of type 'UnsafeMutablePointer<CChar>' (aka 'UnsafeMutablePointer<Int8>') and 'Int'
336 |                     continue
337 |                 }
338 |                 if err != 0 {
    |                        |- error: binary operator '!=' cannot be applied to operands of type 'UnsafeMutablePointer<CChar>' (aka 'UnsafeMutablePointer<Int8>') and 'Int'
    |                        `- note: overloads for '!=' exist with these partially matching parameter lists: (Int, Int)
339 |                     fatalError("strerror_r error: \(err)")
340 |                 }

[marcprux]

@finagolfin does this seem right to you? You mention avoiding using the GNU strerror_r by specifying -Xlinker -landroid-spawn at https://github.com/finagolfin/swift-android-sdk/blob/53495a4adf9695395a65cec2dc2faa75962a4583/swift-android-ci-release.patch#L163C22-L163C32 , but that didn't change anything when I tried it manually.

[compnerd]

This doesn't seem right. I think that this is missing a wrapper (is strerror_r implemented as a macro?

[finagolfin]

You mention avoiding using the GNU strerror_r by specifying -Xlinker -landroid-spawn

No, that flag has nothing to do with strerror_r, either I miswrote or you are misremembering.

@jakepetroules fixed this in #497 last month, but it was reverted later because of an issue on Amazon Linux. If you want to fix this, I suggest you bring back that commit and modify it so it works on that linux distro too.

[marcprux]

It looks like the reversion was #498. @rintaro, did this fix the Amazon Linux linker error?

[rintaro]

did this fix the Amazon Linux linker error?

Yes.

[finagolfin]

Why are you seeing this error on Android in the first place, building this package as a dependency of something else? As that linked pull notes, passing -Xswiftc -Xcc -Xswiftc -U_GNU_SOURCE to SwiftPM should work around that.

[marcprux]

As that linked pull notes, passing -Xswiftc -Xcc -Xswiftc -U_GNU_SOURCE to SwiftPM should work around that.

Yes, -Xswiftc -Xcc -Xswiftc -U_GNU_SOURCE does fix it. I had confused the comment in swift-android-ci-release.patch to think that it was the intention of the -Xlinker -landroid-spawn flag that I mentioned earlier. But it turns out that the linker flag is needed too, of else we hit a bunch of errors like ld.lld: error: undefined symbol: posix_spawnattr_init when linking the test runner executable.

I was hitting this error with my periodic CI for swift-everywhere.org at https://github.com/swift-everywhere/swift-package-builds/actions for swift-package-manager. I've added that flag to the swift-android-action, and it seems to work now, so this can probably be closed unless anyone thinks it is worthwhile to try to fix it in code…

[finagolfin]

I plan to resurrect #497 later, feel free to beat me to it. 😉

[finagolfin]

Looking into it in #500. Btw @marcprux, if you're adding that -U_GNU_SOURCE for all packages, that could break some other package instead (no problem with -landroid-spawn though).

[marcprux]

Looking into it in #500. Btw @marcprux, if you're adding that -U_GNU_SOURCE for all packages, that could break some other package instead

Yeah, I just noticed that swift-nio fails to build with it.

(no problem with -landroid-spawn though).

Actually, I'm seeing that it is failing with ld: library 'android-spawn' not found with the 6.1 nightly SDK but working in 6.0 for some reason.

I'll just remove all the flags and pin my hopes on #500 🥹

[finagolfin]

Actually, I'm seeing that it is failing with ld: library 'android-spawn' not found with the 6.1 nightly SDK but working in 6.0 for some reason.

Huh, that appears to be this bug with macros when cross-compiling and applying command-line flags, perhaps getting worse in 6.1. Can't you just apply some per-package fixes on your CI for now, instead of applying these CLI flags universally?

I'll just remove all the flags and pin my hopes on #500 🥹

That will only fix this repo and those that depend on it not having to -U_GNU_SOURCE, it does nothing for the occasional -landroid-spawn dependency.