Static const vs const in global variable

Question

In Foo.h I define 1 global variable as

static const int g_var = 4;

Then I include this header file in many different header files and .cpp files. If I just write

int g_var = 4;

I get errors "g_var already defined in", which is understandable, so I had to add static so it is just initialized once. But using

const int g_var = 4; 

solves the "already defined in" problem. I read that this is because const global variables have internal linkage by default. So is the keyword static here redundant?

Answer 1

Static keyword is an access specifier. If you use static inside a function it allows the variable to exist outside the function scope and preserve its value between diffrent function calls. If you define a static variable or constant outside a function its scope will be limited to that particular file. With constant, static keyword simply optimizes the complilation.