Re: [PATCH/i386newframe/RFC] DWARF CFI frame unwinder

[Andrew Cagney <ac131313@redhat.com>]

>> 
>> This isn't right.  It should return DW_AT_frame_base.  However, since 
>> dwarf2expr.c doesn't yet use these methods it doesn't [?] really matter. 
>>  Only affects ``info frame''.


> I don't think it should.

Er ...

> The frame's CFA is the basis for identifying the frame and locating
> saved registers in the CFI.  It is always present when you have CFI.
> 
> DW_AT_frame_base is the basis for locating saved variables and locals. 
> It is generally present when you have DWARF-2 debug info.

You and I went through all this not too long ago.  frame-base is for 
this high level thingie, frame-unwind is for the low level register 
information.

> The two are not necessarily related.  I don't remember how we settled
> on providing DW_AT_frame_base.  Possibly a debug info auxiliary to the
> function symbol or to the block.
> 
> 
> By the way, I don't remember something else I believe we've
> discussed...  Does each target that wants to use the CFI unwinder have
> to add it in its gdbarch initialization?

At present yes.

Given the amount of upheval required before a target will work with this 
code, it doesn't really matter.  As I,and now Mark, discovered, it is 
something of an all or nothing afair.

Andrew