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Use the new #available(Android API, *) instead to look for backtrace() #1373

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Use the new #available(Android API, *) instead to look for backtrace() #1373

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2 changes: 2 additions & 0 deletions .github/workflows/pull_request.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,8 @@ jobs:
ios_host_exclude_xcode_versions: '[{"xcode_version": "16.2"}, {"xcode_version": "16.3"}, {"xcode_version": "16.4"}]'
enable_wasm_sdk_build: true
enable_android_sdk_build: true
android_ndk_versions: '["r28c"]'
android_sdk_triples: '["aarch64-unknown-linux-android33", "x86_64-unknown-linux-android28"]'
soundness:
name: Soundness
uses: swiftlang/github-workflows/.github/workflows/[email protected]
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10 changes: 8 additions & 2 deletions Sources/Testing/SourceAttribution/Backtrace.swift
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Expand Up @@ -40,7 +40,7 @@ public struct Backtrace: Sendable {
self.addresses = addresses.map { Address(UInt(bitPattern: $0)) }
}

#if os(Android) && !SWT_NO_DYNAMIC_LINKING
#if compiler(<6.3) && os(Android)
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@aluco100 aluco100 Nov 15, 2025

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why have you changed the order of conditionals here?

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@finagolfin finagolfin Nov 15, 2025

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No particular reason, just the perception that such compiler versioning is more important.

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@aluco100 aluco100 Nov 15, 2025

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which conditional has more complexity, the compiler version check or the os check?

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@finagolfin finagolfin Nov 15, 2025

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No idea what you mean by complexity in this context, I just figured that the compiler check is more generally known by Swift devs.

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@grynspan grynspan Nov 15, 2025

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Actually, compiler() has special powers in the compiler (heh). If it evaluates to false, subsequent conditions are not even parsed. This means that you can write something like #if compiler(>=6.3) && objectFormat(ELF) and an older compiler won't complain that it doesn't know what objectFormat() is.

It's good to get into the habit of putting compiler() first for this reason.

/// The `backtrace()` function.
///
/// This function was added to Android with API level 33, which is higher than
Expand Down Expand Up @@ -76,7 +76,13 @@ public struct Backtrace: Sendable {
initializedCount = .init(clamping: backtrace(addresses.baseAddress!, .init(clamping: addresses.count)))
}
#elseif os(Android)
#if !SWT_NO_DYNAMIC_LINKING
#if compiler(>=6.3)
if #available(Android 33, *) {
initializedCount = addresses.withMemoryRebound(to: UnsafeMutableRawPointer.self) { addresses in
.init(clamping: backtrace(addresses.baseAddress!, .init(clamping: addresses.count)))
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@aluco100 aluco100 Nov 15, 2025

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maybe an if let for baseAddress here?

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@finagolfin finagolfin Nov 15, 2025

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I believe this almost always succeeds- unless the allocation up top fails?- so the unwrapping is a mere formality, but I'm just bringing back Jonathan's earlier code here: I didn't write this.

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@aluco100 aluco100 Nov 15, 2025

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I see, for some reason (correct me I'm wrong) the closure gives you a buggy object with nil property references (such as a de-reference issue) maybe you will lead this into a SIGTRAP I think

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@finagolfin finagolfin Nov 15, 2025

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In my experience, this always works and is a common idiom in the Swift corelibs.

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@grynspan grynspan Nov 15, 2025

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This unwrap cannot fail. Hence the forced unwrap. There is no point in an if let because we know the else case will never be executed.

! is considered acceptable style within the Swift toolchain under these circumstances.

}
}
#else
if let _backtrace {
initializedCount = .init(clamping: _backtrace(addresses.baseAddress!, .init(clamping: addresses.count)))
}
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