1[/ 2 Boost.Optional 3 4 Copyright (c) 2015 - 2018 Andrzej Krzemienski 5 6 Distributed under the Boost Software License, Version 1.0. 7 (See accompanying file LICENSE_1_0.txt or copy at 8 http://www.boost.org/LICENSE_1_0.txt) 9] 10 11 12[section:relnotes Release Notes] 13 14[heading Boost Release 1.73] 15 16* Fixed [@https://github.com/boostorg/optional/issues/78 issue #78]. 17* `boost::none` is now declared as an inline variable (on compilers taht support it): there is only one instance of `boost::none` across all translation units. 18* Fixed a number of compilation errors in GCC 4.4.7 in `optional<T>` for trivial `T`s. Thanks to Robert Leahy for the fix. For details see [@https://github.com/boostorg/optional/pull/80 pr #78]. 19* Now surpressing warning `-Wweak-vtables`. 20 21[heading Boost Release 1.69] 22 23* Remove deprecation mark from `reset()` method (without arguments). 24* Fixed [@https://github.com/boostorg/optional/issues/59 issue #59]. 25* Fixed bug with initialization of certain wrapper types in clang with -std=c++03. See [@https://github.com/boostorg/optional/pull/64 pr #64]. 26 27[heading Boost Release 1.68] 28 29* Added member function `has_value()` for compatibility with `std::optional` ([@https://github.com/boostorg/optional/issues/52 issue #52]). 30* Added member function `map()` for transforming `optional<T>` into `optional<U>` using a function of type `T -> U`. 31* Added member function `flat_map()` for transforming `optional<T>` into `optional<U>` using a function of type `T -> optonal<U>`. 32 33 34[heading Boost Release 1.67] 35 36* Fixed [@https://github.com/boostorg/optional/issues/46 issue #46]. 37* Fixed `-Wzero-as-null-pointer-constant` warnings. 38 39 40[heading Boost Release 1.66] 41 42* On newer compilers `optional` is now trivially-copyable for scalar `T`s. This uses a different storage (just `T` rather than `aligned_storage`). We require the compiler to support defaulted functions. 43* Changed the implementation of `operator==` to get rid of the `-Wmaybe-uninitialized` false-positive warning from GCC. 44 45[heading Boost Release 1.63] 46* Added two new in-place constructors. They work similarly to `emplace()` functions: they initialize the contained value by perfect-forwarding the obtained arguments. One constructor always initializes the contained value, the other based on a boolean condition. 47* Syntax `o = {}` now correctly un-initializes optional, just like in `std::optional`. 48* Fixed [@https://svn.boost.org/trac/boost/ticket/12203 Trac #12203]. 49* Fixed [@https://svn.boost.org/trac/boost/ticket/12563 Trac #12563]. 50 51 52[heading Boost Release 1.62] 53 54* Fixed [@https://svn.boost.org/trac/boost/ticket/12179 Trac #12179]. 55 56 57[heading Boost Release 1.61] 58 59* Now `boost::optional` is specialized for reference parameters. This addresses a couple of issues: 60 * the `sizeof` of optional reference is that of a pointer, 61 * some bugs connected to copying optional references are gone, 62 * all run-time bugs caused by incorrect reference binding on some compilers are now turned into compile-time errors, 63 * you can swap optional references: it is like swapping pointers: shalow, underlying objects are not affected, 64 * optional references to abstract types work. 65* Documented nested typedefs ([@https://svn.boost.org/trac/boost/ticket/5193 Trac #5193]). 66* Made the perfect-forwarding constructor SFINAE-friendly, which fixes [@https://svn.boost.org/trac/boost/ticket/12002 Trac #12002]. However, this only works in the newer platforms that correctly implement C++11 `<type_traits>`. 67* Fixed [@https://svn.boost.org/trac/boost/ticket/10445 Trac #10445]. 68 69 70[heading Boost Release 1.60] 71 72* Changed the implementation of `boost::none` again. Now it is a const object with internal linkage (as any other tag). This fixes [@https://svn.boost.org/trac/boost/ticket/11203 Trac #11203]. 73 74 75[heading Boost Release 1.59] 76 77* For C++03 compilers, added 0-argument overload for member function `emplace()`, and therewith removed the dependency on `<boost/utility/in_place_factory.hpp>`. 78* Fixed [@https://svn.boost.org/trac/boost/ticket/11241 Trac #11241]. 79 80[heading Boost Release 1.58] 81 82* `boost::none_t` is no longer convertible from literal `0`. This avoids a bug where `optional<rational<int>> oi = 0;` would initialize an optional object with no contained value. 83* Improved the trick that prevents streaming out `optional` without header `optional_io.hpp` by using safe-bool idiom. This addresses [@https://svn.boost.org/trac/boost/ticket/10825 Trac #10825]. 84* IOStream operators are now mentioned in documentation. 85* Added a way to manually disable move semantics: just define macro `BOOST_OPTIONAL_CONFIG_NO_RVALUE_REFERENCES`. This can be used to work around [@https://svn.boost.org/trac/boost/ticket/10399 Trac #10399]. 86* It is no longer possible to assign `optional<U>` to `optional<T>` when `U` is not assignable or convertible to `T` ([@https://svn.boost.org/trac/boost/ticket/11087 Trac #11087]). 87* Value accessors now work correctly on rvalues of `optional<T&>` ([@https://svn.boost.org/trac/boost/ticket/10839 Trac #10839]). 88 89 90[heading Boost Release 1.57] 91 92* [@https://github.com/boostorg/optional/pull/9 Git pull #9]: ['"Supply `<string>` to fix C++03 compile error on `logic_error("...")`"]. 93 94 95[heading Boost Release 1.56] 96 97* Added support for rvalue references. Now `optional<T>` works with moveable but non-copyable `T`'s, 98* Improved `swap` (now uses move operations), 99* Added function `emplace()`. This is the last of the requests from [@https://svn.boost.org/trac/boost/ticket/1841 Trac #1841], 100* `optional` is moveable, including conditional `noexcept` specifications, which make it `move_if_noexcept`-friendly, 101* Using explicit operator bool() on platforms that support it ([@https://svn.boost.org/trac/boost/ticket/4227 Trac #4227]) (breaking change), 102* Forward declaration of `operator<<(ostream&, optional const&)` to prevent inadvertent incorrect serialization of optional objects, 103* Removed deprecated function `reset()` from examples ([@https://svn.boost.org/trac/boost/ticket/9005 Trac #9005]), 104* Equality comparison with `boost::none` does not require that `T` be EqualityComparable, 105* Optional rvalue references are explicitly disallowed, 106* Binding temporaries to optional references is explicitly disallowed (breaking change), 107* More ways to access the contained value, functions `value()`, `value_or()`, `value_or_eval()`, 108* Updated and reorganized documentation, added tutorial and quick guide sections. 109 110 111 112[endsect][/ relnotes] 113