C++14, C++17, and C++20 New Features

[bcaddy]

This is some notes I've been taking on the features that new versions of C++ have that we might want to use. At time of writing the main branch is on C++11 and dev is on C++17. Compiler support for features can be found here. This list is far from complete, it is simply the things I've found as useful or potentially useful.

C++14

• std::make_unique for instantiating std::unique_ptrs for arrays
• Required by GoogleTest versions greater than 1.12.1

C++17

Features of C++17

• std::filesystem for better handling of files and directories, especially in system tests
• Return multiple values from a single function via structured binding. Allows things like xid to be declared const and avoid hard to find bugs
• HIP-CPU requires C++17
• operator[] for std::shared_ptr
• inline variables
• Initial support for STL parallel algorithms which can be trivially run on GPU
• Better nested namespaces syntax
• Declare variables in if statements to avoid having them clutter up the higher scope
• if constexpr to force evalutation of if statement at compile time
• Fold Expressions - easier variadic expressions
• Attribute specifier sequences, mostly to silence erroneous "unused variable" warnings

C++20

• std::bitcast to directly copy the bits of one type to another instead of memcpy
• Increased support for STL parallel algorithms on GPU
• Clearer implementation of mathematical constants.
• Better printing for floating point numbers with std::format. link to discussion

C++23