Re: dwarf_begin_elf() won't create handle without .debug_* sections

[Mark Wielaard <mark at klomp dot org>]

On Wed, 2018-05-30 at 17:32 +0000, Sasha Da Rocha Pinheiro wrote:
> I just fixed something interesting in Dyninst. We were assuming that
> the FDEs were following the CIE in the eh_frame section, but this is
> not correct. I found them mixed in an ARM binary and this caused
> wrong parsing. 
> So we I did dwarf_next_cfi() in the loop to go through the FDE's, and
> I had to use it again in the loop to get the corresponding CIE. I
> don't think it's a problem, just kinda not intuitive, for who wants
> to understand after me.

dwarf_next_cfi () is a very low level interface. Other cfi related
interfaces that work with a Dwarf_CFI handle (dwarf_getcfi () and
dwarf_getcfi_elf ()) and don't make any assumptions about the order. 

But they do build up a cache of all entries. In return for some extra
memory usage you can use them without caring about the order in which
they appear with dwarf_cfi_addrframe () by just giving an address you
are interested in and using dwarf_frame_info (), dwarf_frame_cfa () and
 dwarf_frame_register () to extract the information (which might be
less/different than what you would get from the "raw" Dwarf_CFI_Entry).

Cheers,

Mark