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bac5d0e9a1
When Swift imports C structs, it synthesizes an initializer that takes no arguments and zero-initializes the C struct. When C++ interop is enabled, Clang treats all C structs as if they were C++ structs. This means that some of the C structs will get a default constructor implicitly generated by Clang. This implicit default constructor will not zero-initialize trivial fields of the struct. This is a common source of confusion and subtle bugs for developers who try to enable C++ interop in existing projects that use C interop and rely on zero-initialization of C structs. rdar://115909532
67 lines
1.8 KiB
Swift
67 lines
1.8 KiB
Swift
// RUN: %target-run-simple-swift(-I %S/Inputs/ -Xfrontend -enable-experimental-cxx-interop)
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//
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// REQUIRES: executable_test
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import StdlibUnittest
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import Constructors
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var CxxConstructorTestSuite = TestSuite("CxxConstructors")
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CxxConstructorTestSuite.test("ExplicitDefaultConstructor") {
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let instance = ExplicitDefaultConstructor()
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expectEqual(42, instance.x)
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}
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CxxConstructorTestSuite.test("ImplicitDefaultConstructor") {
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let instance = ImplicitDefaultConstructor()
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expectEqual(42, instance.x)
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}
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CxxConstructorTestSuite.test("DefaultedDefaultConstructor") {
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let instance = DefaultedDefaultConstructor()
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expectEqual(42, instance.x)
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}
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CxxConstructorTestSuite.test("MemberOfClassType") {
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let instance = MemberOfClassType()
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expectEqual(42, instance.member.x)
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}
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CxxConstructorTestSuite.test("ConstructorWithParam") {
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let instance = ConstructorWithParam(2)
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expectEqual(44, instance.x)
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}
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CxxConstructorTestSuite.test("TemplatedConstructor") {
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let arg = ArgType(i: 2)
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let instance = TemplatedConstructor(arg)
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expectEqual(2, instance.value.i)
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}
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CxxConstructorTestSuite.test("implicit default ctor") {
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// Make sure that fields of C++ structs are zeroed out.
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let instance1 = ConstructorWithParam()
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expectEqual(0, instance1.x)
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let instance2 = IntWrapper()
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expectEqual(0, instance2.x)
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// CopyAndMoveConstructor is not default-initializable in C++, however, Swift
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// generates an implicit deprecated default constructor for C++ structs for
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// compatibility with C. This constructor will zero out the entire backing
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// memory of the struct, including fields that have an init expression.
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// See `SwiftDeclSynthesizer::createDefaultConstructor`.
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let instance3 = CopyAndMoveConstructor()
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expectEqual(0, instance3.value)
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expectNil(instance3.ptr)
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}
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runAllTests()
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