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Make constants immortal #3063

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Merged
merged 1 commit into from
Aug 27, 2021
Merged

Make constants immortal #3063

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6 changes: 5 additions & 1 deletion CoreFoundation/Base.subproj/CFBase.h
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Original file line number Diff line number Diff line change
Expand Up @@ -686,7 +686,11 @@ CFTypeRef CFMakeCollectable(CFTypeRef cf) CF_AUTOMATED_REFCOUNT_UNAVAILABLE;

#if DEPLOYMENT_RUNTIME_SWIFT

#define _CF_SWIFT_RC_PINNED_FLAG (0x1)
#if TARGET_RT_64_BIT
#define _CF_SWIFT_RC_PINNED_FLAG (0x80000004ffffffff)
#else
#define _CF_SWIFT_RC_PINNED_FLAG (0x800004FF)
#endif
#define _CF_CONSTANT_OBJECT_STRONG_RC ((uintptr_t)_CF_SWIFT_RC_PINNED_FLAG)
#endif

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29 changes: 29 additions & 0 deletions Tests/Foundation/Tests/TestBridging.swift
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Expand Up @@ -27,6 +27,7 @@ class TestBridging : XCTestCase {
return [
("testBridgedDescription", testBridgedDescription),
("testDynamicCast", testDynamicCast),
("testConstantsImmortal", testConstantsImmortal),
]
}

Expand Down Expand Up @@ -70,4 +71,32 @@ class TestBridging : XCTestCase {
let anyArray: Any = [TestClass()]
XCTAssertNotNil(anyArray as? NSObject)
}

func testConstantsImmortal() throws {
func release(_ ptr: UnsafeRawPointer, count: Int) {
let object: Unmanaged<NSNumber> = Unmanaged.fromOpaque(ptr)
for _ in 0..<count {
object.release()
}
}

let trueConstant = NSNumber(value: true)
let falseConstant = NSNumber(value: false)

// To accurately read the whole refcount, we need to read the second
// word of the pointer.
let truePtr = unsafeBitCast(trueConstant, to: UnsafePointer<Int>.self)
let falsePtr = unsafeBitCast(falseConstant, to: UnsafePointer<Int>.self)

let trueRefCount = truePtr.advanced(by: 1).pointee
let falseRefCount = falsePtr.advanced(by: 1).pointee

XCTAssertEqual(trueRefCount, falseRefCount)
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I'm not sure we need to actually verify the reference count, so much as verify that releasing it a bunch then using it doesn't crash.

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It's actually important that it doesn't change. Otherwise we are just masking the problem by assigning a very high ref count.


release(truePtr, count: 5)
release(falsePtr, count: 5)

XCTAssertEqual(trueRefCount, truePtr.advanced(by: 1).pointee)
XCTAssertEqual(falseRefCount, falsePtr.advanced(by: 1).pointee)
}
}