Compiler Warning (level 4) C4211

nonstandard extension used : redefined extern to static

With the default Microsoft extensions (/Ze), you can redefine an extern identifier as static.

Example

// C4211.c
// compile with: /W4
extern int i;
static int i;   // C4211

int main()
{
}

Such redefinitions are invalid under ANSI compatibility (/Za).