bitwizeshift / bit-stl Goto Github PK

AppVeyor has not successfully built this library on either of the two target compilers:

• MSVC
• clang-cl

Known issues:

clang-cl

• Doesn't fully support exception handling correctly
  • Fails to compile Catch unit tests (due to try/catch statements)
  • Fails to compile anything that throws

C++17 introduces optional (of which, bit::stl::optional is based on for pre-c++17 support).

optional satisfies nullable stack values; however it does not play nice when used in composition, since the bool member pushes additional padding when used in arrays, or when a member immedately succeeds an optional member.

For this, there are two proposed types:

• bit::stl::optional_array -- an array of optional values that behaves like std::array<T,N> where value_type is T* (with nullptr representing not-set). This would allow N optionals to be stored contiguously, with N bools indicating their construction to also be contiguous.
• bit::stl::optional_tuple -- a tuple of values that may or may not contain a value. This is a generalization of optional_array, where each member may be a different type. The bools indicating initialization is stored contiguously in memory, which optimizes storage.

The utility type variant is noticeably absent from this library, and should be added as a future extension

The previous implementation of expected was based on Alexandrescu's Expected<T> type. This type, along with the error-code equivalent, checked, have been removed from the version 2 release of this library.

With recent standard proposals, a better alternative of expected<T,E> has been suggested that satisfies nearly all requirements for both of the original expected and checked types. This will supersede the old version.

As discovered in the bit-memory library, gsl::byte (which bit::stl::byte is based on) violates c++ strict-aliasing when using it to alias in place of a char*. C++17 fixes this with std::byte and additional wording to single-unit fundamental types -- but without C++17, the byte type is useless.

Any uses of bit::stl::byte will require updating as well, such as bit::stl::span