STL: malloc_alloc - omission of types

[Shoban Jeyaraj]

Hello,

I am an newbiew with respect to creating custom allocator. Currently,
we are in the process of creating a custom allocator. Going through
most of the example, we have one which requires to specify the type
while specifying the allocator:

Eg: vector<int, my_allocator<int> > foo;

I know that the default allocator malloc_alloc does not require the
type.

Eg: vector<int, malloc_alloc> foo;

I am wondering how it is implemented. Going through the STL source
(stl_alloc) does not help me much. Hope someone can clarify.

Regards,
Shoban Jayaraj

 

[Nick Hounsome]

Hello,

I am an newbiew with respect to creating custom allocator. Currently,
we are in the process of creating a custom allocator. Going through
most of the example, we have one which requires to specify the type
while specifying the allocator:

Eg: vector<int, my_allocator<int> > foo;

I know that the default allocator malloc_alloc does not require the
type.

malloc_alloc is not the default allocator.

Eg: vector<int, malloc_alloc> foo;

I am wondering how it is implemented. Going through the STL source
(stl_alloc) does not help me much. Hope someone can clarify.

Where are you getting your "STL" source from?

Regards,
Shoban Jayaraj

P.S. I think it is highly unlikely that this is a good idea anyway.

 

[Alberto Barbati]

I know that the default allocator malloc_alloc does not require the
type.

Are you, by chance, using a very old SGI STL implementation? You should
know that allocators changed a lot since that implementation was
written. That implementation, although still good and honorable, is now
far from "standard". In particular, SGI STL allowed the member function
allocate() to return a void* but the C++ standard now mandates that it
shall return a typed pointer. That's why malloc_alloc does not require a
type but conforming allocators do.

Alberto