Forwarding Arguments with std::forward
In C 0x, std::forward is used to forward arguments to another function call. This is advantageous when you want to avoid having to explicitly copy or move the arguments.
The usage of std::forward involves using the &&& notation in the function parameters. This notation allows you to accept both lvalue and rvalue references as arguments.
In the example given:
<code class="cpp">template<class T>
void foo(T&&& arg)
{
bar(std::forward<T>(arg));
}</code>
The std::forward
However, you should not use std::forward in all cases. It is only necessary when you need to preserve the reference type of the argument. For example, if you have a function that does not take rvalue references, you should not use std::forward.
In the following example:
<code class="cpp">template<int val, typename... Params>
void doSomething(Params... args) {
doSomethingElse<val, Params...>(args...);
}</code>
You do not need to use std::forward because the doSomethingElse function can take lvalue or rvalue references.
However, if you have a function that does take rvalue references, you should use std::forward to ensure that the arguments are forwarded as rvalue references. For example:
<code class="cpp">template<int val, typename... Params>
void doSomething(Params&&... args) {
doSomethingElse<val, Params...>(std::forward<Params>(args)...);
}</code>
In this example, std::forward is used to ensure that the arguments are forwarded as rvalue references, even if they are initially lvalue references.
Finally, you should not forward an argument multiple times. This can lead to undefined behavior. For example, the following code is incorrect:
<code class="cpp">template<int val, typename... Params>
void doSomething(Params&&... args) {
doSomethingElse<val, Params...>(std::forward<Params>(args)...);
doSomethingWeird<val, Params...>(std::forward<Params>(args)...);
}</code>
In this example, the arguments are forwarded twice, which can lead to undefined behavior.
The above is the detailed content of ## When Should I Use std::forward in C ?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
C Polymorphism : is function overloading a kind of polymorphism?
Jun 20, 2025 am 12:05 AM
Yes, function overloading is a polymorphic form in C, specifically compile-time polymorphism. 1. Function overload allows multiple functions with the same name but different parameter lists. 2. The compiler decides which function to call at compile time based on the provided parameters. 3. Unlike runtime polymorphism, function overloading has no extra overhead at runtime, and is simple to implement but less flexible.
What Are the Different Kinds of Polymorphism in C ? Explained
Jun 20, 2025 am 12:08 AM
C has two main polymorphic types: compile-time polymorphism and run-time polymorphism. 1. Compilation-time polymorphism is implemented through function overloading and templates, providing high efficiency but may lead to code bloating. 2. Runtime polymorphism is implemented through virtual functions and inheritance, providing flexibility but performance overhead.
C : Is Polymorphism really useful?
Jun 20, 2025 am 12:01 AM
Yes, polymorphisms in C are very useful. 1) It provides flexibility to allow easy addition of new types; 2) promotes code reuse and reduces duplication; 3) simplifies maintenance, making the code easier to expand and adapt to changes. Despite performance and memory management challenges, its advantages are particularly significant in complex systems.
C Destructors: Common Errors
Jun 20, 2025 am 12:12 AM
C destructorscanleadtoseveralcommonerrors.Toavoidthem:1)Preventdoubledeletionbysettingpointerstonullptrorusingsmartpointers.2)Handleexceptionsindestructorsbycatchingandloggingthem.3)Usevirtualdestructorsinbaseclassesforproperpolymorphicdestruction.4
C tutorial for people who know Python
Jul 01, 2025 am 01:11 AM
People who study Python transfer to C The most direct confusion is: Why can't you write like Python? Because C, although the syntax is more complex, provides underlying control capabilities and performance advantages. 1. In terms of syntax structure, C uses curly braces {} instead of indentation to organize code blocks, and variable types must be explicitly declared; 2. In terms of type system and memory management, C does not have an automatic garbage collection mechanism, and needs to manually manage memory and pay attention to releasing resources. RAII technology can assist resource management; 3. In functions and class definitions, C needs to explicitly access modifiers, constructors and destructors, and supports advanced functions such as operator overloading; 4. In terms of standard libraries, STL provides powerful containers and algorithms, but needs to adapt to generic programming ideas; 5
Polymorphism in C : A Comprehensive Guide with Examples
Jun 21, 2025 am 12:11 AM
Polymorphisms in C are divided into runtime polymorphisms and compile-time polymorphisms. 1. Runtime polymorphism is implemented through virtual functions, allowing the correct method to be called dynamically at runtime. 2. Compilation-time polymorphism is implemented through function overloading and templates, providing higher performance and flexibility.
What Are the Various Forms of Polymorphism in C ?
Jun 20, 2025 am 12:21 AM
C polymorphismincludescompile-time,runtime,andtemplatepolymorphism.1)Compile-timepolymorphismusesfunctionandoperatoroverloadingforefficiency.2)Runtimepolymorphismemploysvirtualfunctionsforflexibility.3)Templatepolymorphismenablesgenericprogrammingfo
C Destructors: Practical Code Examples
Jun 22, 2025 am 12:16 AM
C destructorsarespecialmemberfunctionsthatautomaticallyreleaseresourceswhenanobjectgoesoutofscopeorisdeleted.1)Theyarecrucialformanagingmemory,filehandles,andnetworkconnections.2)Beginnersoftenneglectdefiningdestructorsfordynamicmemory,leadingtomemo
