#define FB_CKMAG(_ptr, _magic, _str) {  \
        if( !(_ptr) )  { \
                fb_log("ERROR: null %s ptr, file %s, line %d\n", \
                        _str, __FILE__, __LINE__ ); \
                abort(); \
        } \
        else \
        if ((_magic) != (_ptr->if_magic))       { \
                fb_log("ERROR: bad %s ptr x%x, s/b x%x, was x%x, file %s, line %
                        _str, _ptr, _magic, \
                        *((long *)(_ptr)), __FILE__, __LINE__ ); \
                abort(); \
        } \
        return; \
        }