Question

In the process of automatically renaming many variables in a big project I may have created a lot of things like these:

class Foo {
    int Par;
    void Bar(int Par) {
        Par = Par;       // Nonsense
    }
};

Now I need to identify those locations to correct them. E.g. into “this->Par = Par;”.
Unfortunately the Visual C++ Compiler des not give me any comment about it even with all warnings on.
I remember there once was a warning about it. It said “Code has no effect” or something. But it seems to be gone maybe because some people used that practice to avoid “unreferenced parameter” warnings.
Is there a way to re-activate that warning?
Does GCC warn here?
Any Idea?

Answer 1

A couple of compilers can generate warnings on this:

• GCC and Clang can warn on code like this if you add the -Wshadow option. (Specifically, while they don’t warn about the meaningless assignment, they do warn about the local variable Par shadowing the member variable Par – you may or may not like this.)
• Embarcadero C++Builder does not warn that Par = Par is useless, but it can warn that Par isn’t used after it’s assigned to, which should meet your needs.

I suspect a tool like PC-Lint could also identify code like this.

Another solution is to mark your parameters as const:

class Foo {
    int Par;
    void Bar(const int Par) {
        Par = Par;       // Compiler error!
    }
};

const on pass-by-value parameters is not part of the function signature, so you only need to add it to the function definitions within your .cpp file, not your function declarations within your .h file. In other words, it’s legal to do this:

// foo.h
class Foo {
    int Par;
    void Bar(int Par);
};

// foo.cpp
void Foo::Bar(const int Par) { ... }