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25 lines
916 B
25 lines
916 B
4 years ago
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In Objective-C, calling a method on `nil` (or in Objective-C terms, sending a message to `nil`) does not crash,
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it simply returns a falsy value (nil/0/false). However, sending a message that returns
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a non-POD C++ type (POD being ["Plain Old Data"](https://en.cppreference.com/w/cpp/named_req/PODType), essentially
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anything that cannot be compiled as a C-style struct) to `nil` causes undefined behaviour.
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```objectivec
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std::shared_ptr<int> callMethodReturnsnonPOD() {
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SomeObject* obj = getObjectOrNil();
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std::shared_ptr<int> d = [obj returnsnonPOD]; // UB
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return d;
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}
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```
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To fix the above issue, we need to check if `obj` is
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not `nil` before calling the `returnsnonPOD` method:
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```objectivec
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std::shared_ptr<int> callMethodReturnsnonPOD(bool b) {
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SomeObject* obj = getObjectOrNil(b);
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if (obj == nil) { return std::make_shared<int>(0); }
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std::shared_ptr<int> d = [obj returnsnonPOD];
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return d;
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}
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```
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