constexpr variable cannot have non literal type
How does constexpr work in C++?
constexpr indicates that the value, or return value, is constant and, where possible, is computed at compile time.
A constexpr integral value can be used wherever a const integer is required, such as in template arguments and array declarations.21 fév. 2023What is the difference between const and constexpr variables in C++?
These expressions are very similar in functionality to const ; in fact, all constexpr variables are const by default.
However, there are a few key differences.
The most important difference is that constexpr values are initialized at compile-time rather than runtime.What is a literal type in constexpr?
Literal types are the types of constexpr variables and they can be constructed, manipulated, and returned from constexpr functions.
Note: the standard doesn't define a named requirement with this name.
This is a type category defined by the core language.
It is included here as a named requirement only for consistency.26 déc. 2023The constexpr specifier declares that it is possible to evaluate the value of the function or variable at compile time.
Such variables and functions can then be used where only compile time constant expressions are allowed (provided that appropriate function arguments are given).30 oct. 2023
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Constexpr consternation
08.09.2011 [temp.dep.constexpr]p2 identifies constants with literal type ... a class with a non-constant in-class initializer cannot have any constexpr ... |
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Constexpr Introduction - Scott Schurr - CppCon 2015.key
constexpr objects can't change at runtime Static data member of literal type static constexpr char who[] ... calculations might not have the same. |
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Constexpr and inline Variables in Modern C++17
The only types usable within a constexpr context are literal types. A constant expression or constexpr function may also not invoke a non constexpr function |
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Constexpr Lambda
28.04.2015 constructors can not be evaluated as core constant expressions (since closure objects are non-literal types). |
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Constexpr Introduction - Scott Schurr - CppCon 2015.key
constexpr objects can't change at runtime Static data member of literal type static constexpr char who[] ... calculations might not have the same. |
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Guidelines for the use of the C++14 language in critical and safety
Most of the rules are typical coding guidelines i.e. how to write code. A project shall not contain instances of non-volatile variables being given. |
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Templates
Non-type template parameters are placeholders for certain values constexpr variables must have literal type and be immediately initialized. |
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Constexpr Applications - Scott Schurr - CppCon 2015.key
Static data member of literal type error: constexpr variable 'mask' must be initialized by a ... Can't default cmp to std::less; it's not constexpr. |
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Generalized Constant Expressions — Revision 3
24.04.2006 Therefore a constexpr variable can always be used as part of a constant expression. As for other const variables storage need not be ... |
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Generalized Constant Expressions—Revision 3
24.04.2006 Therefore a constexpr variable can always be used as part of a constant expression. As for other const variables storage need not be ... |
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Constexpr Lambda - Standard C++
28 avr 2015 · literal type if the type of each of its data-members is a literal type; expressions; either because those functions can not be specified I'm confident we'll have a good answer for lambdas + constexpr in C++17 constraints by avoiding: goto; static, thread_local, non-literal and uninitialized variable 10 |
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Generalized Constant Expressions - Bjarne Stroustrups Homepage
26 fév 2006 · the proposal for Literals for user-defined types [Str03], Generalized initializer lists [DRS03], Initializer A constant-expression function cannot be called before it is defined static constexpr int val; // constexpr variable }; constexpr As for other const variables, storage need not be allocated for a constant- |
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Constexpr Introduction - Scott Schurr - CppCon 2015key
constexpr objects can't change at runtime calculations might not have the same results as Not virtual • Returns • Literal type or • Reference to literal type • Parameters must be error: constexpr variable 'mask' must be initialized by a |
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Permitting trivial default initialization in constexpr contexts - Open-std
15 juil 2019 · default initialization does not compile in constexpr the need for this proposed change As always, undefined behavior cannot be invoked in constexpr (3 4 4) - a definition of a variable of non-literal type or of static or |
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N2235 - Open-std
17 avr 2007 · constructed from “sufficiently simple” constructors (constexpr constructors ) The proposal the proposal for Literals for user-defined types [Str03], Generalized initializer A constant-expression function cannot be called before it is As for other const variables, storage need not be allocated for a constant- |
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Extern template constexpr - Squarespace
Today I have Daniele Parastrelli's guest post about extern templates for you It was thought to start in (C++20 or later) If the constexpr variable is not the following requirements: the return type of c++20 (up to C++20) must be literal in its return Destructors cannot be constexpr, but constant expressions can implicitly call |
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Михаил Матросов
non-volatile non-template non-inline const-qualified variables (including constexpr) that aren't declared extern and aren't previously declared to have external linkage; 11 #define n 42 // Cannot contain expressions; simply evil const int n = 42; const std::string s4 = "4"; // If not a literal type; implicitly static // Anywhere |
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ARM® Compiler Errors and Warnings Reference Guide
78: a parameter declaration may not have an initializer 79: expected a type 229: bit field cannot contain all values of the enumerated type 1134: literal treated as "long long" 3646: a constexpr variable declaration must be a definition |
