Re: [boost] ASIO into the standard

Daniel James skrev 2014-07-11 22:06:

On 11 July 2014 20:49, Glen Fernandes wrote:

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On Fri, Jul 11, 2014 at 12:18 PM, Felipe Magno de Almeida wrote:

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This looks very arbitrary to me. Is there any wording in the standard that supports that allocators have to be used only for allocation of value_type (or classes that has a value_type in it)?

My understanding is that the allocators have to be used for all dynamic allocation. If this is not explicitly worded in the standard, then it should be. Otherwise allocators simply are not as useful with any other interpretation.

I looked this up earlier, as I thought the same. 23.2.1.7 says:

"Unless otherwise specified, all containers defined in this clause obtain memory using an allocator (see 17.6.3.5)."

Which suggests to me that all allocation is done using the allocator. I suppose debug info could be considered something that isn't obtained by the container, as it can be external, but I wouldn't have thought that for things like buckets.

Well, it says "obtain memory", not "obtain *all* memory". :-)

23.2.1.3 says:

"For the components affected by this subclause that declare an allocator_type, objects stored in these components shall be constructed using the allocator_traits::construct function and destroyed using the allocator_traits::destroy function (20.7.8.2). These functions are called only for the container’s element type, not for internal types used by the container."

But that's specifying construction, not allocation (btw. I get this wrong in unordered, I'll fix it soon).

Right. At least one implementation used construct and destroy on internal pointers, like node pointers in std::list. This section clarifies that they should not do that. Bo Persson