Re: New allocator uses global memory

From: Gavin Lambert (boost_at_[hidden])
Date: 2020-01-09 22:28:08

On 7/01/2020 21:11, Frederick Gotham wrote:
> I propose a new allocator that uses global (i.e. static duration) memory.

This looks somewhat like an "arena allocator".  You'll find many 
existing examples using that keyword.

When specifically applied to vector, you might also want to look at 
static_vector:

 
https://www.boost.org/doc/libs/1_72_0/doc/html/boost/container/static_vector.html

> T *allocate(std::size_t const n)
> 	{
> 		if (n > t_capacity)
> 			throw std::bad_alloc();
> 
> 		return buf;
> 	}

Except this is more dangerous than a real arena allocator, since it's 
single-shot.  If the collection tries to make more than one allocation, 
this will return the same pointer each time, potentially corrupting the 
data.

This makes it incompatible with list-like containers, and possibly risky 
even with std::vector, depending on how its resize operation is 
implemented.  Using static_vector instead is much safer.