On Tue, Jul 30, 2013 at 06:05:00PM +0400, Andrey Ponomarenko wrote:
> I created a dump of a library debug-info by the "eu-readelf
> --debug-dump=info" command. The formal_parameter of a subprogram has
> type "(GNU_ref_alt) [ N]", but N is not described anywhere in the
> I have take a look at the source code of elfutils and found, that
> DW_FORM_GNU_ref_alt is an offset in the "alternate debuginfo":
> DW_FORM_GNU_ref_alt = 0x1f20, /* offset in alternate .debuginfo. */
> DW_FORM_GNU_strp_alt = 0x1f21 /* offset in alternate .debug_str. */
> How can I read/dump this "alternate debuginfo"?
DWARF extensions elfutils recognizes/supports are described at:
When configured with --enable-dwz libdw will resolve these FORMs.
The new forms are described in this DWARF5 proposal:
You can find the alt dwz file by reading the .gnu_debugaltlink section.
Which contains a file name followed by the build-id of the dwz file.
Resolving the build-id is done in the regular way as described at
The build-id symlink will point at the /usr/lib/debug/.dwz/ file.
What is the best way to read the file name from .gnu_debugaltlink section?
I've tried objdump:
$> eu-objdump -s -j .gnu_debugaltlink
Contents of section .gnu_debugaltlink:
0000 2e2e2f2e 2e2f2e64 777a2f4f 43452d30 ../../.dwz/OCE-0
0010 2e31322d 312e6663 31382e78 38365f36 .12-1.fc18.x86_6
0020 3400f971 c94aa7b5 33115f63 bbc3d3ed 4..q.J..3._c....
0030 88f7cdb6 ae09 ......
So the path to the alternate debug info file is
"../../.dwz/OCE-0.12-1.fc18.x86_64", but it's not so easy to parse it
from the output.
Andrey Ponomarenko, ROSA Lab.