Re: [avr-gcc-list] avr-gcc 4.2.2 atmega 2561 issues

[Simon Eatough]

Ok 
So after some reading it appears that the problem is due to avr-gcc's use of  
16 bit function pointers, and means that calls to glibc that are over the 
128k boundary are broken.
Simon


On Tue, 16 Dec 2008 15:49:34 Simon Eatough wrote:
> Hi folks
> I've got a project where the code has just crossed the dreaded 128k
> boundary. Specifically glibc straddles the boundary.
> I've got problems with the code crashing,  due i think to call of
> si_to_float in libgcc  which sets up the Z register for the eijmp in
> __prolog_saves__  ,but does not set EIND . causing the eijmp instruction to
> jump to the wrong address.
>
> disassembly below.
>
> si_to_float (SItype arg_a)
> {
>    1fee4:   a8 e0           ldi r26, 0x08   ; 8
>    1fee6:   b0 e0           ldi r27, 0x00   ; 0
>    1fee8:   e8 e7           ldi r30, 0x78   ; 120
>    1feea:   ff ef           ldi r31, 0xFF   ; 255
>    1feec:   0d 94 7f 04     jmp 0x208fe ; 0x208fe <__prologue_saves__+0x12>
>    1fef0:   9b 01           movw    r18, r22
>    1fef2:   ac 01           movw    r20, r24
>   fp_number_type in;
>
> /snip
>
>
> 000208ec <__prologue_saves__>:
>    208ec:   2f 92           push    r2
>    208ee:   3f 92           push    r3
>    208f0:   4f 92           push    r4
>    208f2:   5f 92           push    r5
>    208f4:   6f 92           push    r6
>    208f6:   7f 92           push    r7
>    208f8:   8f 92           push    r8
>    208fa:   9f 92           push    r9
>    208fc:   af 92           push    r10
>    208fe:   bf 92           push    r11
>    20900:   cf 92           push    r12
>    20902:   df 92           push    r13
>    20904:   ef 92           push    r14
>    20906:   ff 92           push    r15
>    20908:   0f 93           push    r16
>    2090a:   1f 93           push    r17
>    2090c:   cf 93           push    r28
>    2090e:   df 93           push    r29
>    20910:   cd b7           in  r28, 0x3d   ; 61
>    20912:   de b7           in  r29, 0x3e   ; 62
>    20914:   ca 1b           sub r28, r26
>    20916:   db 0b           sbc r29, r27
>    20918:   0f b6           in  r0, 0x3f    ; 63
>    2091a:   f8 94           cli
>    2091c:   de bf           out 0x3e, r29   ; 62
>    2091e:   0f be           out 0x3f, r0    ; 63
>    20920:   cd bf           out 0x3d, r28   ; 61
>    20922:   19 94           eijmp
>
>
> Wonder if there is a workaround for this ?
>
> Cheers
> Simon
>
>
> --
> Simon Eatough
> Development Engineer
> Pertronic Industries
> Wellington NZ
>
>
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-- 
Simon Eatough
Development Engineer
Pertronic Industries
Wellington NZ

tel +4445673229x808