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jandrewrogers a day ago

What does RAII have to do with any of the above?

WD-42 a day ago | parent | next [-]

0 allocations after the program initializes.

tialaramex a day ago | parent | next [-]

RAII doesn't imply allocating.

My guess is that you're assuming all user defined types, and maybe even all non-trivial built-in types too, are boxed, meaning they're allocated on the heap when we create them.

That's not the case in C++ (the language in question here) and it's rarely the case in other modern languages because it has terrible performance qualities.

Gupie a day ago | parent | prev | next [-]

Open a file in the constructor, close it in the destructor. RAII with 0 allocations.

dh2022 a day ago | parent [-]

std::vector<int> allocated and freed on the stack will allocate an array for its int’s on the heap…

Gupie 10 hours ago | parent | next [-]

Sure, but my point was that RAII doesn't need to involve the heap. Another example would be acquiring abd releasing a mutex.

usefulcat 19 hours ago | parent | prev [-]

I've heard that MSVC does (did?) that, but if so that's an MSVC problem. gcc and clang don't do that.

https://godbolt.org/z/nasoWeq5M

menaerus 17 hours ago | parent [-]

WDYM? Vector is an abstraction over dynamically sized arrays so sure it does use heap to store its elements.

aw1621107 7 hours ago | parent [-]

I think usefulcat interpreted "std::vector<int> allocated and freed on the stack" as creating a default std::vector<int> and then destroying it without pushing elements to it. That's what their godbolt link shows, at least, though to be fair MSVC seems to match the described GCC/Clang behavior these days.

nicoburns a day ago | parent | prev | next [-]

RAII doesn't necessarily require allocation?

jjmarr a day ago | parent | prev [-]

Stack "allocations" are basically free.

grougnax 16 hours ago | parent [-]

No. And they're unsafe. Avoid them at all costs.

DashAnimal a day ago | parent | prev | next [-]

Well if you're using the standard library then you're not really paying attention to allocations and deallocations for one. For instance, the use of std::string. So I guess I'm wondering if you work in an industry that avoids std?

jandrewrogers a day ago | parent [-]

I work in high-scale data infrastructure. It is common practice to do no memory allocation after bootstrap. Much of the standard library is still available despite this, though there are other reasons to not use the standard containers. For example, it is common to need containers that can be paged to storage across process boundaries.

C++ is designed to make this pretty easy.

nmhancoc a day ago | parent | prev | next [-]

Not an expert but I’m pretty sure no exceptions means you can’t use significant parts of std algorithm or the std containers.

And if you’re using pooling I think RAII gets significantly trickier to do.

theICEBeardk a day ago | parent [-]

https://en.cppreference.com/w/cpp/freestanding.html to see the parts you can use.

astrobe_ a day ago | parent | prev [-]

And what does "modern" has to do with it anyway.