国产av日韩一区二区三区精品,成人性爱视频在线观看,国产,欧美,日韩,一区,www.成色av久久成人,2222eeee成人天堂

Table of Contents
"Undefined Reference to" Template Class Constructor
Issue
Solution
Approach 1: Explicit Template Instantiation
Approach 2: Move Implementation to Header Files
Header File vs Translation Unit
Conclusion
Home Backend Development C++ Why Do I Get an 'Undefined Reference to' Error with Template Class Constructors in C ?

Why Do I Get an 'Undefined Reference to' Error with Template Class Constructors in C ?

Dec 13, 2024 pm 05:55 PM

Why Do I Get an

"Undefined Reference to" Template Class Constructor

In C programming, template classes are often used to provide generic functionality that can be instantiated with different types. However, sometimes when instantiating a template class, you may encounter an "undefined reference to" error.

This error occurs when the compiler cannot find the implementation for the constructor of the template class. The compiler typically needs to see the implementation of the constructor in order to generate the code for the instantiated class.

Issue

In the provided code, the template class cola is defined in cola.h header file, but the implementation is in the cola.cpp file. When compiling the program, the compiler sees the template declaration in main.cpp and attempts to implicitly instantiate the cola class with float and string types.

However, since the compiler has not yet seen the implementation of the constructor in cola.cpp, it cannot generate the code for these instantiated classes, resulting in the "undefined reference to" error.

Solution

There are two approaches to resolve this issue:

Approach 1: Explicit Template Instantiation

Add explicit template instantiations at the end of the cola.cpp file:

template class cola<float>;
template class cola<string>;

This explicitly instructs the compiler to generate code for the cola template class with the specified types.

Approach 2: Move Implementation to Header Files

Move the implementation of the template class constructor and member functions into the header file (cola.h and nodo_colaypila.h).

This ensures that the compiler sees the implementation when it instantiates the template class, eliminating the need for explicit instantiation.

Header File vs Translation Unit

In Approach 1, explicit instantiation is done at the end of the translation unit (a single compiled file). This means that all code in that file must be compiled before the instantiation.

In Approach 2, the implementation is in the header file, which is included in every translation unit that uses the template class. As a result, the implementation is available to the compiler regardless of the order of compilation.

Conclusion

Both approaches are valid solutions to the "undefined reference to" error with template classes. The choice depends on the specific needs of the project. Explicit instantiation is more flexible and allows for better control over which template specializations are generated. However, moving the implementation to header files is more common and provides more flexibility in using the template class.

The above is the detailed content of Why Do I Get an 'Undefined Reference to' Error with Template Class Constructors in C ?. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

C   Polymorphism : is function overloading a kind of polymorphism? 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 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? 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 C Destructors: Common Errors Jun 20, 2025 am 12:12 AM

C destructorscanleadtoseveralcommonerrors.Toavoidthem:1)Preventdoubledeletionbysettingpointerstonullptrorusingsmartpointers.2)Handleexceptionsindestructorsbycatchingandloggingthem.3)Usevirtualdestructorsinbaseclassesforproperpolymorphicdestruction.4

Polymorphism in C  : A Comprehensive Guide with Examples 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  ? 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   tutorial for people who know Python 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

C   Polymorphism: Coding Style C Polymorphism: Coding Style Jun 19, 2025 am 12:25 AM

C polymorphismisuniqueduetoitscombinationofcompile-timeandruntimepolymorphism,allowingforbothefficiencyandflexibility.Toharnessitspowerstylishly:1)Usesmartpointerslikestd::unique_ptrformemorymanagement,2)Ensurebaseclasseshavevirtualdestructors,3)Emp

See all articles