Let’s sunset C/C++

Re:Let’s sunset C/C++ by steveklabnik on Friday August 14, 2015 @02:14PM (#10061780)

   > I don't follow that logic,

Specifically, I mean that when the vector changes size, the vector needs to reallocate. In Rust, since there are no move constructors, it's just a memcpy of the whole chunk of memory, one big one. Very straightforward and fast. In C++, you need to call all those move constructors.

  > The original becames null because the semantic is actually tranfering ownership

Absolutely. In Rust, this is tracked at compile time, and attempting to use after the move is a compile-time error. In C++, you'll get a null pointer dereference. (I _think_ that technically it's in an 'unspecified' state, not a null one, but on my system, null is what I get).

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Re:Let’s sunset C/C++ by pmelendez on Friday August 14, 2015 @03:15PM (#10062199)

> mean that when the vector changes size, the vector needs to reallocate You can control how often the vector changes the size and a lot of times you can even prevent that.

> In Rust, since there are no move constructors, it's just a memcpy.

memcpy is actually slower that move the ownership of a buffer, that's why you avoid copying as much as you can (std::vector also uses memcpy inside).

> In Rust, this is tracked at compile time, and attempting to use after the move is a compile-time error.

It is nice to get a misuse at compile time, but my point is that once you transfer the ownership of the pointer you shouldn't be using that unique_ptr anymore. I'm probably biased but I don't see this "accidental" misuse happening often (tbh I haven't seen it ever and I have seen some horrible things in C++ before)

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Re:Let’s sunset C/C++ by steveklabnik on Friday August 14, 2015 @04:05PM (#10062576)

  > (std::vector also uses memcpy inside).

I don't think I am communicating myself clearly, so I'll just bow out about this issue, until I have an example ready. I should write one anyway, I just don't have it at the moment.

  > I'm probably biased but I don't see

this "accidental" misuse happening > often

While that may be true, as the article points out, all it takes is for someone, anywhere, to slip up once, and then you possibly have a serious security violation. Having the compiler double-check your work is nice.

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