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This attribute can be attached to a noncopyable struct to specify that its storage is raw, meaning the type definition is (with some limitations) able to do as it pleases with the storage. This provides a basis for implementing types for things like atomics, locks, and data structures that use inline storage to store conditionally-initialized values. The example in `test/Prototypes/UnfairLock.swift` demonstrates the use of a raw layout type to wrap Darwin's `os_unfair_lock` APIs, allowing a lock value to be stored inside of classes or other types without needing a separate allocation, and using the borrow model to enforce safe access to lock-guarded storage.
19 lines
855 B
Swift
19 lines
855 B
Swift
// RUN: %empty-directory(%t)
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// RUN: %target-swift-frontend -enable-experimental-feature RawLayout -emit-module-path %t/a.swiftmodule -module-name a %s
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// RUN: llvm-bcanalyzer -dump %t/a.swiftmodule | %FileCheck --check-prefix BC-CHECK --implicit-check-not UnknownCode %s
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// RUN: %target-swift-ide-test -print-module -module-to-print a -source-filename x -I %t | %FileCheck --check-prefix MODULE-CHECK %s
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// BC-CHECK: <RawLayout_DECL_ATTR
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// MODULE-CHECK: @_rawLayout(size: 5, alignment: 4) struct A_ExplicitSizeAlign
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@_rawLayout(size: 5, alignment: 4)
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struct A_ExplicitSizeAlign: ~Copyable {}
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// MODULE-CHECK: @_rawLayout(like: T) struct B_Cell
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@_rawLayout(like: T)
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struct B_Cell<T>: ~Copyable {}
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// MODULE-CHECK: @_rawLayout(likeArrayOf: T, count: 8) struct C_SmallVector
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@_rawLayout(likeArrayOf: T, count: 8)
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struct C_SmallVector<T>: ~Copyable {}
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