How Can I Create and Use Dynamic Shared C Class Libraries on Linux?
Dec 05, 2024 am 05:12 AMDynamic Shared C Class Libraries on Linux
Introduction
Creating and utilizing shared class libraries in C on Linux can be a challenging task. This article provides a comprehensive guide that covers the process of creating and using shared C class libraries, including object creation, modification, and destruction.
Creating a Shared C Class Library
To create a shared C class library, follow these steps:
- Define the class interface: Create a header file (.h) that declares the class interface, including member variables and methods.
- Implement the class methods: Create a source file (.cc) that implements the class methods.
- Export the library functions: Use "extern 'C'" to export the functions that will be used to create and destroy library objects.
- Compile the library: Compile the header and source files into a shared library using the appropriate flags (-shared on Linux, -dynamiclib on macOS).
Using a Shared C Class Library
To use a shared C class library that has been created, follow these steps:
- Load the library: Use dlopen() to load the shared library into memory.
- Resolve function symbols: Use dlsym() to resolve the addresses of the exported functions.
- Create and use library objects: Use the function pointer retrieved from dlsym() to create objects of the library class and call their methods.
- Destroy library objects: When finished, use the destruction function pointer to properly destroy the library objects.
Example Implementation
The following code snippets demonstrate a simple shared C library (myclass.h, myclass.cc) and a C program (class_user.cc) that utilizes the library:
myclass.h:
class MyClass { public: MyClass(); virtual void DoSomething(); private: int x; };
myclass.cc:
extern "C" MyClass* create_object() { return new MyClass; } extern "C" void destroy_object(MyClass* object) { delete object; } MyClass::MyClass() { x = 20; } void MyClass::DoSomething() { cout << x << endl; }
class_user.cc:
MyClass* (*create)(); void (*destroy)(MyClass*); create = (MyClass* (*)())dlsym(handle, "create_object"); destroy = (void (*)(MyClass*))dlsym(handle, "destroy_object"); MyClass* myClass = (MyClass*)create(); myClass->DoSomething(); destroy(myClass);
Compilation (Linux):
g++ -fPIC -shared myclass.cc -o myclass.so g++ class_user.cc -ldl -o class_user
By following these steps, you can successfully create and use dynamic shared C class libraries on Linux.
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