c++ - Does this self-assignment do something sensible?

Question

I just found this line of code within a function, which puzzles me. Can this make sense in any context or it is undefined behavior?

char * acFilename = acFilename;

EDIT: The compiler complains with Warning C4700, that I am using an uninitialized variable.

Answer 1

At block scope, in C++, this is undefined behaviour, as the right-hand side reads the variable the variable before it has been initialized (C++14 [dcl.init]/12).

At block scope, in C11, this could either be undefined behaviour or behave as an uninitialized variable, depending on various details of the implementation and the rest of the function, see here for detailed analysis.

At namespace scope, in C++, it is OK well-defined and makes a null pointer. This is because all static variables are zero-initialized before their initializers are considered. (C++14 [basic.start.init]/2).

At file scope in C, it is a constraint violation; static variables must have a constant expression as initializer, and the value of a variable cannot be a constant expression.