Re: [boost] [any] [basic_any] This seems like a little pearl in Boost 1.77, but it's a bit underdocumented?

Hi Antony, *- No. For what were you planning to rely on that? (allocating the object at the first bytes of the any)* Assuming the object is allocated inside the boost::any, there might be optimization opportunities for the compiler as const T& value = *reinterpret_cast(&any) would be a valid way to access the contained value. (Note that I said might, I'm not sure of this). I'll take a look of what I thought was missing in the documentation when I have time (quite busy with a release for the moment) Best /Viktor On Mon, Sep 13, 2021 at 12:11 PM Antony Polukhin wrote:

On Fri, Aug 20, 2021, 14:24 Viktor Sehr via Boost wrote:

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I just discovered basic_any which is a very nice addition for me. However it's a bit under-documented for the moment.

Thanks! Glad to hear that.

It's quite hard to write a good docs, I'd appreciate help. Feel free to provide PRs to adjust the docs https://github.com/boostorg/any/blob/b4d7770db49979bfc22bdeb4c8e7ca1a39ad1e3...

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For example: - I assume it's stack-allocated, does it allocate on the heap if assigned an object larger than the stack (like small_vector) or is this not allowed (like static_vector)?

Yes, it allocates on the heap if the object does not fit. It's documented here, somewhere between the lines https://www.boost.org/doc/libs/1_77_0/doc/html/boost/anys/basic_any.html

- An idea would also be to add a flag which breaks compilation if an object

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larger than the OptimizeForSize argument is assigned?

Good idea. Please fill a feature request https://github.com/boostorg/any/issues

- (For detail) If allocated on the stack, are the first bytes of the

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basic_any the same as the contained object?

No. For what were you planning to rely on that?

/Viktor

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