[fpc-devel] dwarf 2 warning CIE

[Dimitrios Chr. Ioannidis]

Hi,

Στις 2/2/2021 7:33 μ.μ., ο/η Dimitrios Chr. Ioannidis via fpc-devel έγραψε:
> Hi,
>
> On 2021-02-02 18:47, Christo Crause wrote:
>> On Tue, Feb 2, 2021 at 12:28 PM Dimitrios Chr. Ioannidis via fpc-devel
>> <fpc-devel at lists.freepascal.org> wrote:
>>
>>> Reading dwarf information with avr-embedded-objdump.exe --dwarf
>>> returns
>>> : "avr-embedded-objdump.exe: Warning: Invalid CIE pointer 0x00c80000
>>> in
>>> FDE at 0x000014"
>>
>> I get the same warning on Linux using avr-objdump (GNU objdump (GNU
>> Binutils) 2.26.20160125), your test code and all of the dwarf debug
>> options in the compiler.  Not sure if this is really a problem when
>> debugging with gdb, I've managed to debug across units before.  Do you
>> have a reproducible problematic debug situation that can be tested?
>
>  I checked with the dwarf 2.o specification and I read that "in FDE 
> (Frame Description Entry) there is a CIE_pointer field which is a 
> uword constant offset into the .debug_frame section that denotes the 
> CIE that is associated with this FDE."
>
>
>  AFAIU, both are used, among others of course, to provide virtual 
> unwind information to debugger . But here there is a problem, IMO, the 
> FDE has an CIE_id of fd39e538 but there is none CIE with that id. 
> There is only one CIE with id ffffffff .


Correction ! There is only one CIE with id 00000000 not ffffffff ( copy 
past error, sorry ).


>
>
> "dwarf_CIE_FDE_Bug.elf:     file format elf32-avr
>
> Contents of the .debug_frame section:
>
>
> 00000000 0010 ffffffff CIE
>   Version:               1
>   Augmentation:          ""
>   Code alignment factor: 1
>   Data alignment factor: -4
>   Return address column: 24
>
>   DW_CFA_def_cfa: r32 ofs 2
>   DW_CFA_offset_extended: r36 at cfa+0
>   DW_CFA_nop
>
> 00000014 0000 00c80000 FDE cie=fd39e538 pc=0002..0002"
>
>
> Of course I maybe be wrong and this is not a problem.
>
> regards,
>
> -- 
> Dimitrios Chr. Ioannidis
>
>
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