[Bug debug/54568] New: Unused codes in unwind-dw2-fde.c on PT_GNU_EH_FRAME targets

[Bug debug/54568] New: Unused codes in unwind-dw2-fde.c on PT_GNU_EH_FRAME targets

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54568

             Bug #: 54568
           Summary: Unused codes in unwind-dw2-fde.c on PT_GNU_EH_FRAME
                    targets
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hjl.tools@gmail.com


From

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24724#c15

--
On a system whose linker supports --eh-frame-hdr, we will use the version of
_Unwind_Find_FDE in unwind-dw2-fde-dip.c.  It will override the version in
unwind-dw2-fde.c by renaming it via #define.  This file is selected by
libgcc/config/t-eh-dw2-dip.  It will still call the version of
_Unwind_Find_FDE, but that function will only look through files registered by
__register_frame_info_bases.  __register_frame_info_bases is called by
crtstuff.c, but it is only called on systems whose linker does not support
--eh-frame-hdr.
--

On PT_GNU_EH_FRAME targets, even __register_frame_info_bases isn't
defined/used, we still include unwind-dw2-fde.c and call its
_Unwind_Find_FDE as _Unwind_Find_registered_FDE.  Should we skip
the whole thing?

[Bug debug/54568] Unused codes in unwind-dw2-fde.c on PT_GNU_EH_FRAME targets

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54568

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at redhat dot com

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> 2012-09-13 15:50:08 UTC ---
It is needed by crtbeginT.o for -static since PT_GNU_EH_FRAME isn't
used for static executables.  However, dl_iterate_phdr works fine
with libc.a from glibc.  Jakub, do you remember why PT_GNU_EH_FRAME
isn't used on static executables?

[Bug debug/54568] Unused codes in unwind-dw2-fde.c on PT_GNU_EH_FRAME targets

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54568

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-09-13 16:11:12 UTC ---
Think about libraries built with older GCC versions or built with older
binutils.  Those would still call the register routines instead of building
.eh_frame_hdr.

[Bug debug/54568] Unused codes in unwind-dw2-fde.c on PT_GNU_EH_FRAME targets

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54568

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> 2012-09-13 16:18:24 UTC ---
(In reply to comment #2)
> Think about libraries built with older GCC versions or built with older
> binutils.  Those would still call the register routines instead of building
> .eh_frame_hdr.

We are talking static executables here.  .eh-frame-hdr section is generated by
the linker to create static executable and we know --eh-frame-hdr works with
the linker.  Why shouldn't --eh-frame-hdr work for static executable linked
with libraries built with older GCC versions or built with older binutils?

[Bug debug/54568] --eh-frame-hdr should also be enabled for static executable

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54568

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Unused codes in             |--eh-frame-hdr should also
                   |unwind-dw2-fde.c on         |be enabled for static
                   |PT_GNU_EH_FRAME targets     |executable

--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> 2012-09-13 22:23:08 UTC ---
The old interface is needed for DSO and executable created by
the older binutils.  However, it has nothing to with -static.
Also for Android targets, there is no old DSO.