C++23: Removing garbage collection support

Re:C++23: Removing garbage collection support by senderista on Wednesday November 01, 2023 @05:41PM (#38105747)

Here's a much simpler example of something impossible in C++ and trivial in Rust: how about a non-nullable unique_ptr? The constructor should just be able to check for null and then no code need ever check for null again, right? Sorry, you need an invalid state to represent a moved-from instance, so this is impossible.

Are you telling me that having to accommodate invalid states that are semantically both unnecessary and undesirable is not a serious limitation of C++ move semantics?

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Re:C++23: Removing garbage collection support by fluoridation on Wednesday November 01, 2023 @06:02PM (#38105943)

Following the previous example, you wrap std::unique_ptr in another class that has no move constructor and forwards constructor parameters to std::make_unique(), and can also be constructed from an std::unique_ptr. Now you have a heap-allocated smart pointer class that can't possibly be null.

Alternatively, you make it movable, and if someone tries to call operator*(), operator->(), or get() on the null value, you throw an exception. Not as clean, but, hey, it's safe.

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