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Re: [libunwind] problems parsing dwarf frame info on amd64 optimized cod
Re: [libunwind] problems parsing dwarf frame info on amd64 optimized code
Fri, 12 Mar 2004 10:12:57 -0800
>>>>> On Mon, 8 Mar 2004 10:49:45 -0800, Max Asbock <address@hidden> said:
Max> Hi all,
Max> I am trying to parse the dwarf frame info on amd64 using
Max> libunwind which I had to slightly modify to run on amd64.
Max> The parser works correctly in unoptimized code that uses frame pointers.
Max> When I turn on the -O flag things fall apart. This is with gcc 3.2.2.
Max> The parser finds two rules in the CIE:
Max> CFA_def_cfa r7+0x8 (rsp)
Max> CFA_offset r16 at cfa-0x8 (return address)
Max> and then in the FDE it finds:
Max> CFA_def_cfa_offset <offset>
Max> This works for stepping from the first frame to the second, but
Max> on the next step it fails, since the CFA is read again from r7 (rsp)
Max> which hasn't changed. And it seems that the CFA <offset> is the
Max> offset relative to the current CFA, not relative to the value in rsp.
Hmmh, I suspect the bug is in apply_reg_state(). It probably should
use c->cfa instead of unw_get_reg() "under the right circumstances".
I'll see if I can reproduce the problem with x86. What test-case did