C++23

The current revision of the C++ standard.

New language features

• New language feature testing macros
• Explicit object parameter, explicit object member functions, a.k.a. "deducing this" (P0847R7)
• Multidimensional subscript operator (e.g. v[1, 3, 7] = 42;) (P2128R6)
• static operator[] (P2589R1), static operator(), and static lambdas (P1169R4)
• auto(x) and auto{x}: decay-copy in the language (P0849R8)
• Assumptions via new attribute [[assume(expression)]] (P1774R8)
• Attributes on lambda-expressions (P2173R1)
• Optional extended floating-point types: std::float{16|32|64|128}_t, and std::bfloat16_t (P1467R9)
• New preprocessor directives: #elifdef, #elifndef (P2334R1), and #warning (P2437R1)
• Literal suffix 'Z'/'z' for (signed) std::size_t literals (P0330R8), e.g. auto ouz = 0uz;
• White-spaces trimming before line splicing. (P2223R2)
• Simpler implicit move (P2266R3)
• Extending the lifetime of temporaries in range-based for loop initializer (P2718R0)
• CTAD from inherited constructors (P2582R1)
• Labels at the end of compound statements (P2324R2), e.g.
  

void f(int& x)
{
if (x)
goto END;
x = 42;
END:
}

• Alias declarations (using) in init-statements (P2360R0), e.g.
  

for (using T = int; T e : v)
/* ... */

• Make () more optional for lambda expressions (P1102R2)
• Narrowing contextual conversions to bool in static_assert and if constexpr (P1401R5)
• Make declaration order layout (of non-static class data members) mandated (P1847R4)
• Text encoding changes:
  • Character sets and encodings (P2314R4)
  • Consistent character literal encoding (P2316R2)
  • Named universal character escapes, e.g. "\N{CAT FACE}" for "🐱" (P2071R2)
  • Delimited escape sequences, e.g. "\o{7777}", "\x{C0DE}", "\u{CAFE}" (P2290R3)
  • Support for UTF-8 as a portable source file encoding (P2295R6)
• if consteval / if not consteval (P1938R3)
• constexpr changes:
  • Non-literal variables, labels, and gotos in constexpr functions (P2242R3)
  • Permitting static and thread_local variables in constant expressions in constexpr functions (P2647R1)
  • constexpr function does not need its return type and parameter types to be literal type (P2448R2)
  • constexpr function for which no invocation satisfies the requirements of a core constant expression (P2448R2)

New library features

• New library feature testing macros

New modules

• std and std.compat (P2465R3)

New headers

• <expected>
• <flat_map>