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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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16 changes: 4 additions & 12 deletions Sources/Testing/SourceAttribution/Backtrace.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -40,16 +40,6 @@ public struct Backtrace: Sendable {
self.addresses = addresses.map { Address(UInt(bitPattern: $0)) }
}

#if os(Android) && !SWT_NO_DYNAMIC_LINKING
/// The `backtrace()` function.
///
/// This function was added to Android with API level 33, which is higher than
/// our minimum deployment target, so we look it up dynamically at runtime.
private static let _backtrace = symbol(named: "backtrace").map {
castCFunction(at: $0, to: (@convention(c) (UnsafeMutablePointer<UnsafeMutableRawPointer?>, CInt) -> CInt).self)
}
#endif

/// Get the current backtrace.
///
/// - Parameters:
Expand Down Expand Up @@ -77,8 +67,10 @@ public struct Backtrace: Sendable {
}
#elseif os(Android)
#if !SWT_NO_DYNAMIC_LINKING
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You can get rid of this #if.

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I thought so too initially, but the alternative is Android with static linking, in which case it will hit the final #else clause below and error.

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That's not what we use SWT_NO_DYNAMIC_LINKING for. We use it to indicate if dlsym() or equivalent is available. (I named it bad.) So you can just remove it. All Android codepaths will go through here. Even statically-linked Android binaries should be able to use weakly-linked NDK symbols.

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I see, I thought you meant remove just the #if, meaning adding an &&. I kept the check based on your adding it before and misreading this doc, will remove it.

Unsure how this will interact with static linking executables, given the dynamic linking issue I mentioned, but considering most will static link this into shared libraries eventually, may not matter.

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@grynspan's suggestion makes sense - testing requires dynamic linking (i.e. you cannot statically link the testing framework). We know that the platform supports dynamic symbol resolution and because this is within the testing framework, you will be dynamically linking. As a result, just the new handling for the lookup is needed.

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You can in fact statically link Swift Testing!

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In any case, we agreed on removing this check, which he had added, not me.

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Yarp.

if let _backtrace {
initializedCount = .init(clamping: _backtrace(addresses.baseAddress!, .init(clamping: addresses.count)))
if #available(Android 33, *) {
initializedCount = addresses.withMemoryRebound(to: UnsafeMutableRawPointer.self) { addresses in
.init(clamping: backtrace(addresses.baseAddress!, .init(clamping: addresses.count)))
}
}
#endif
#elseif os(Linux) || os(FreeBSD) || os(OpenBSD)
Expand Down