Re: [msp430-elf] Dwarf line numbers not being encoded properly?

[Orlando Arias <orlandoarias at gmail dot com>]

Greetings,

Thank you for your time and your response. Yes, back during last
September, there was a conversation regarding the proper behaviour of
the tools regarding this particular issue. The Dwarf specification was
brought up and it was discussed that it was particularly unclear what
the proper behaviour should be, hence the confusion on which tool is at
fault.

I saw your other message with the patch included, and I can confirm it
works (just finished rebuilding the entire toolchain and testing it).
Thank you very much for all your assistance.

Cheers,
Orlando.

On 01/27/2016 05:32 PM, Kevin Buettner wrote:
> On Wed, 27 Jan 2016 15:22:18 -0500
> Orlando Arias <orlandoarias@gmail.com> wrote:
> 
>> Thank you for your reply. At the moment, I have a patch which was kindly
>> given to me by Simon Marchi which makes GDB utilize the readelf
>> algorithm to obtain line numbers from the binary. We were never sure
>> which tool was at fault (if gdb for not reading dwarf information
>> properly, binutils for not encoding it properly, or gcc for not
>> generating it properly), so I did not pursue the issue for a while.
>>
>> With the new release of binutils, I decided to "reopen" the case, as the
>> distribution I am doing this for prefers using pristine sources from
>> upstream rather than applying patches to work around issues. Besides, if
>> there is something I am doing incorrectly or a bug in a tool, I would
>> rather have that fixed instead.
>>
>> For reference, I have attached the patch that Simon Marchi provided. It
>> applies cleanly to the GDB sources but if the problem is elsewhere, I
>> would have it fixed correctly (hence the temporary workaround comment in
>> there). Again, thank you.
> 
> I've looked over Simon's patch.  I think it's a fine patch to use
> as a work around.
> 
> I think that GDB should detect size mismatches between the CU and the
> encoding of the address associated with DW_LNE_set_address.  It should
> issue a complaint when this mismatch is detected.
> 
> It's not clear to me if GDB should take any action beyond that.  The
> DWARF4 standard says:
> 
>     The DW_LNE_set_address opcode takes a single relocatable address
>     as an operand.  The size of the operand is the size of an address
>     on the target machine.  It sets the address register to the value
>     given by the relocatable address and sets the op_index register to
>     0.
> 
> The key point here is that second sentence.  If we could be certain
> that incorrect behavior would never result by going ahead and using
> the readelf algoritm, then I think it makes sense to go ahead and
> use that algorithm.  Otherwise, I think we need to be content with
> issuing a complaint or perhaps a warning.  (In gdb, complaints are 
> usually not seen unless they're explicitly turned on.)
> 
> You've probably already seen it, but in case you haven't, here's a link
> to my patch for gas:
> 
> https://sourceware.org/ml/binutils/2016-01/msg00304.html
> 
> Kevin
>

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