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Modern C++ does give you move semantics, which makes RAII a lot more expressive, especially with smart pointers. One things about RAII that I find is that, a b

Modern C++ does give you move semantics, which makes RAII a lot more expressive, especially with smart pointers. One things about RAII that I find is that, a bit like inheritance, it's actually not something you have actually do nearly as much as the emphasis it gets in the first chapters of all the books implies. How often do you actually write a move constructor or even a destructor in workaday code? Most of it is done for you by the stdlib (unique_ptr, say) or libraries. Of course it needs to be understood, and understood well, but it feels like landing a plane: you have know it well and it's not unusual and certainly not wrong, but also flying is mostly doing things other than landings.

tialaramex 1y ago
The C++ 11 move is terrible because it's not the move semantic people actually wanted - which is what people took to calling "destructive" move, the feature Rust provides - instead it's this weird confection where we're scooping the guts out of one object and transferring them into a new object, leaving something hollow behind in order to satisfy the requirements of 1980s C++ programs. In some cases this can be optimised to the same machine code, but not always, and semantically it's not what we actually wanted anyway. In terms of RAII this means arranging that after the move the "moved from" object remembers it no longer has any resources and so when it is destroyed it won't clean up - much easier to just design the language properly.
ninkendo 1y ago
RAII, like a lot of C++ concepts, finds the most use in library-like code (stdlib especially), where it needs to be super generic. Application developers get the benefits of these concepts by simply using these libraries, even if they don't have to care about them themselves. As an application developer, you mostly focus on classes as plain-old-data and functions to work on them, so you don't need to mess about with custom destructors or move-constructors or other RAII stuff.

tialaramex 1y ago

The C++ 11 move is terrible because it's not the move semantic people actually wanted - which is what people took to calling "destructive" move, the feature Rust provides - instead it's this weird confection where we're scooping the guts out of one object and transferring them into a new object, leaving something hollow behind in order to satisfy the requirements of 1980s C++ programs. In some cases this can be optimised to the same machine code, but not always, and semantically it's not what we actually wanted anyway. In terms of RAII this means arranging that after the move the "moved from" object remembers it no longer has any resources and so when it is destroyed it won't clean up - much easier to just design the language properly.

ninkendo 1y ago

RAII, like a lot of C++ concepts, finds the most use in library-like code (stdlib especially), where it needs to be super generic. Application developers get the benefits of these concepts by simply using these libraries, even if they don't have to care about them themselves. As an application developer, you mostly focus on classes as plain-old-data and functions to work on them, so you don't need to mess about with custom destructors or move-constructors or other RAII stuff.