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Comment by gibsjose | Hacker News Reader

If you are using an RTOS (which many timing-critical applications run on), you should be worried about memory allocations happening under the hood.

If you don't have full control over when memory is being allocated/reallocated, your system is now non-deterministic.

With pure C, you can know exactly when those few extra instructions for resizing your dynamic array are going to happen.

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Same in C++. There's `std::vector::reserve`, which grows the vector's underlying physical buffer, without logically adding any new elements. If you `reserve` enough capacity before inserting anything, it's even a `O(1)` operation.

Vector and possibly string have that. The vast majority of STL structures do not.

All containers from the C++ standard library (please don't call it STL, that's Stepanov's original library) can be parameterized by an allocator. You can use whatever allocation policy you like best. However, most people use the default allocator because it's good enough.

In any case, while C++ has lots of defects, “loss of control relative to what C gives you” isn't one of them.

Yeah, that's true.

(a bit of topic - but I'm humbly trying to learn more...) I've got zero experience writing allocators. Is there some common ones you use provided somewhere? Do you write your own? (in which case can you point me to where to learn to do that properly)

I don't write allocators myself, but Boost has a pool allocator library [http://www.boost.org/doc/libs/1_60_0/libs/pool/doc/html/inde...], which conforms to the Allocator concept defined in the standard library [http://en.cppreference.com/w/cpp/concept/Allocator].

Thank you

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