Definition (in php_xdebug.h):
ZEND_BEGIN_MODULE_GLOBALS(xdebug)
    int           status;
    int           reason;
...
    zend_bool  do_scream;
ZEND_END_MODULE_GLOBALS(xdebug)
Using:
    if (XG(remote_enabled) && XG(context).handler->register_eval_id && fse->function.type == XFUNC_EVAL) {
        eval_id = XG(context).handler->register_eval_id(&(XG(context)), fse);
    }
In other .c files:
ZEND_EXTERN_MODULE_GLOBALS(xdebug)