API Evolution and Deprecation History

API Evolution and Deprecation History
Prev	Appendix B. + Porting and Maintenance + +	Next

+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