[avr-gcc-list] How .weak?

[Kang Tin LAI]

Hi,

I have some questions, the C startup code of AVR libc:

; These too can be set with the avr-ld --defsym name=value option
; (MCUCR must be set up correctly to enable external SRAM).
        .weak   __init_mcucr__
        .weak   __init_emcucr__
        .weak   __init_wdtcr__

... stuff skipped

#ifdef WDTCR
        ldi     r_tmp1, lo8(__init_wdtcr__)
        wdr
        out     WDTCR, r_tmp1
#endif
#ifdef MCUCR
        ldi     r_tmp1, lo8(__init_mcucr__)
        out     MCUCR, r_tmp1
#endif
#ifdef EMCUCR
        ldi     r_tmp1, lo8(__init_emcucr__)
        out     EMCUCR, r_tmp1
#endif


1. .weak is AVR specific directive?
2. .weak  __init_mcucr__ will allocate a storage? Or just define
   a symbol?
3. What value will be assigned to WDTCR, MCUCR and EMCUCR
   after instructions above? Zero sure? Assume no --defsym option.

Thank you very much!

KTL