Why Does Accessing a Static Class Variable from a Non-Static Method in C Cause an Undefined Reference?

Accessing Static Class Variable from Non-Static Method

In C , when encountering an undefined reference to a static variable, such as in the given code snippet, the issue usually lies in the lack of a definition for that variable.

In the example provided, where the code attempts to access the static variable x from within the non-static method foo, it's important to note that foo is not a static function. Therefore, to resolve this issue, a definition for Helloworld::x must be provided outside of the class definition.

int Helloworld::x = 0; // Provide an initial value or leave uninitialized

Once the static variable is defined, the non-static method foo can access and modify it without requiring foo to be static itself.

void Helloworld::foo() {
     Helloworld::x = 10;
}

By providing a definition for the static member variable, the compiler can locate its memory address and resolve the undefined reference.

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