API Evolution and Deprecation History

API Evolution and Deprecation History
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A list of user-visible changes, in chronological order

Error handling in iostreams cleaned up, made consistent.

`3.4`

Large file support.

Extensions for generic characters and char_traits added in ext/pod_char_traits.h.

Support for wchar_t specializations of basic_filebuf enhanced to support UTF-8 and Unicode, depending on host. More hosts support basic wchar_t functionality.

Support for char_traits beyond builtin types.

Conformant allocator class and usage in containers. As part of this, the following extensions are added: ext/bitmap_allocator.h, ext/debug_allocator.h, ext/mt_allocator.h, ext/malloc_allocator.h,ext/new_allocator.h, ext/pool_allocator.h.

This is a change from all previous versions, and may require source-level changes due to allocator-related changes to structures names and template parameters, filenames, and file locations. Some, like __simple_alloc, __allocator, __alloc, and _Alloc_traits have been removed.

Default behavior of std::allocator has changed.

Previous versions prior to 3.4 cache allocations in a memory pool, instead of passing through to call the global allocation operators (i.e., __gnu_cxx::pool_allocator). More recent versions default to the simpler __gnu_cxx::new_allocator.

Previously, all allocators were written to the SGI style, and all STL containers expected this interface. This interface had a traits class called _Alloc_traits that attempted to provide more information for compile-time allocation selection and optimization. This traits class had another allocator wrapper, __simple_alloc<T,A>, which was a wrapper around another allocator, A, which itself is an allocator for instances of T. But wait, there's more: __allocator<T,A> is another adapter. Many of the provided allocator classes were SGI style: such classes can be changed to a conforming interface with this wrapper: __allocator<T, __alloc> is thus the same as allocator<T>.

The class allocator used the typedef __alloc to select an underlying allocator that satisfied memory allocation requests. The selection of this underlying allocator was not user-configurable.

Table B.6. Extension Allocators

Allocator (3.4)	Header (3.4)	Allocator (3.[0-3])	Header (3.[0-3])
`__gnu_cxx::new_allocator<T>`	`ext/new_allocator.h`	`std::__new_alloc`	`memory`
`__gnu_cxx::malloc_allocator<T>`	`ext/malloc_allocator.h`	`std::__malloc_alloc_template<int>`	`memory`
`__gnu_cxx::debug_allocator<T>`	`ext/debug_allocator.h`	`std::debug_alloc<T>`	`memory`
`__gnu_cxx::__pool_alloc<T>`	`ext/pool_allocator.h`	`std::__default_alloc_template<bool,int>`	`memory`
`__gnu_cxx::__mt_alloc<T>`	`ext/mt_allocator.h`
`__gnu_cxx::bitmap_allocator<T>`	`ext/bitmap_allocator.h`

Releases after gcc-3.4 have continued to add to the collection of available allocators. All of these new allocators are standard-style. The following table includes details, along with the first released version of GCC that included the extension allocator.

Table B.7. Extension Allocators Continued