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

Andrew Cagney
2003-05-05T14:08:26Z

>>
>> 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