Let's have the following example:
-------------------------
static bool flag = false;

void
function_01(void)
{
    if(flag) {
        // some code
    } else {
        // some other code
    }
}

int
main(int argc, char** argv)
{
    return 0;
}
----------------------------
The add the following function _before_ "static bool flag" declaration:
void
function_02(void)
{
    if(flag) {
        // code
    }
}
The editor does not mark "flag" global variable usage as error, but it's actually declared _after_ the function_02() body.