Using a local variable of the same name in another part of the application

Declaring a variable like this:

int MyVariableName;

creates it as visible across all translation units. Even if you don’t use it as “extern int MyVariableName;” somewhere else, it’s still visible across all files.

If you go and do the same thing again, create a variable of the same name, even though you are only using it locally within that file and aren’t using extern, you’re going to get a GCC “multiple definition of” error because the linker tries to link them together and it’s see a conflict.

It should be static

static int MyVariableName;

The static keyword creates a variable that is not visible across translation units.