No linker error when global variable declared static in the header file [duplicate]

Question

Possible Duplicate:
Static variables in C++

// x.h
int i = 3;

// x1.cpp
#include"x.h"
//...

// x2.cpp
#include"x.h"
//...

Above code will give linker error. However If I declare,

//x.h
static int i = 3;

It doesn't give linker error in gcc, even we have the same #include! Are we creating different static int i; for every .cpp file ? Will it cause any silent linking bug (due to same name)?

Answer 1

When C code is compiled, it's one "translation unit" at a time. Early on, #includes are expanded into the text of the referenced files. So what you've got in the static case is equivalent to x1.cpp saying static int i = 3; and x2.cpp doing the same. And static in this context means roughly "don't share this with other translation units."

So yes, when you use static there you are making two different i variables which have nothing to do with each other. This will not cause a linking error.