Re: [boost] Re: what happened to allocators in boost?

From: E. Gladyshev (egladysh_at_[hidden])
Date: 2003-08-27 01:41:44

--- Daryle Walker <dwalker07_at_[hidden]> wrote:
> On Monday, August 25, 2003, at 2:57 PM, Peter Dimov wrote:
> has-bugs/is-slow/plain-old-sucks?  There can be an orthogonal need for 
> a different allocator class, which no improvement on the default one 
> can fix.
> 
> In this case, the Java user is 100% screwed since they can't change the 
> memory manager at all.  Or at least, can't change the manager without 
> changing it everywhere.  (Allocator policies allow mix-and-match.)

I am glad that boost is not a Java library. :)
Don't get me wrong, boost is an amazing library. 
I am learning from it every minute I look at it,
great job guys  thank you.
However I was a bit shocked when I realized how 
ignorant boost is about memory policies. 
For instance boost::signals use std::vector<>, 
but it doesn't care to do anything about the allocator parameter.
Some libraries would mix global new/delete calls with user defined 
memory policies and all that under the covers and the list goes on and on.

I don't like the STL allocators too much but I'd like to 
see a modern C++ library that has consistent and 
clear memory policies.

Instead of having an allocator template parameter 
for each class, perhaps we could design a global 
memory management class that can be scaled horizontally
on the data type basis.
It will require some way to associate a user defined allocator 
with data type.
Then we would need to define STL-style allocators that 
will call the boost memory manager.

The boost memory policy could be along the lines:

1. All boost classes have to use boost::allocator<> 
with STL allocators internally. 
   std::vector<int, boost::allocator<int> >;

2. If a boost class needs to create an object it must call boost::mm.
    int *x = boost::getmm()->create<int>(1);
     ...
    boost::getmm()->destroy(x,1);

3. The user can customize memory policies for her class by calling regmm
    boost::getmm()->regmm( MyAllocator<MyClass>() );

IMHO, in terms of memory management, this simple 
policy will make boost to look more like a C++ library not Java.

It doesn't provide the flexibility of STL allocators but it
does give the user some control over the memory.

Eugene

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