Re: Questions about ``[PATCH] GCC side of .eh_frame_hdr support (take 3)''

[Richard Henderson <rth at redhat dot com>]

On Wed, Apr 24, 2002 at 01:09:42PM -0500, Loren James Rittle wrote:
> Are these optimized EH frames readable by the unwinder in unwind-dw2-fde.c?

Yes.  There is nothing unusual about these modified EH frames.
We eliminated some duplicate information is all.

> Do I need to add this to the port's configuration file for any port
> that might someday use GNU ld 2.12+? (Based on comment in alpha/elf.h,
> I suspect it is not strictly required when unwind-dw2-fde.c is used by
> a port.)
> 
> #if defined(HAVE_LD_EH_FRAME_HDR)
> #define LINK_EH_SPEC "%{!static:--eh-frame-hdr} "
> #endif

It is not required until

  (1) The OS implements dl_iterate_phdr or some equivalent functionality,
  (2) unwind-dw2-fde.c is suitably modified (a-la unwind-dw2-fde-glibc)
      to use (1).

> (I should not ask the obvious question: Why is something which depends
>  solely upon the GNU ld version being added on a per-port basis?
>  Perhaps adding it to config/elfos.h would have been wiser.  Oh well.)

*shrug*  I suppose Jakub was trying to save a bit of space in
the binary for those systems that never use the eh-frame-hdr.

> (I suspect so.)  Does this likely mask a binutils and/or gcc port bug
> that should be tracked down?

Likely a binutils bug.

> The only difference I could detect with readelf(1) between GNU ld
> 2.12.1 without --traditional-format and GNU ld 2.12.1 with
> --traditional-format was the size of .eh_frame:

Look at the output of readelf -wf.

> Trick question: What does --traditional-format mean to GNU ld 2.12.1
> when it *is* the native linker for the system? ;-)

Don't fiddle with the bits.  ;-)


r~